The motivation behind the work lies in a quiet revolution in the drug pipeline. Under the Biopharmaceutical Classification System, and its more modern cousin the Developability Classification System, orally administered drugs are sorted into four classes according to how soluble they are in gastrointestinal fluids and how easily they permeate intestinal membranes. In earlier eras, most new medicines fell into classes I and III, compounds with no real solubility problems. Today, the majority of new drug candidates are poorly soluble molecules belonging to classes II and IV, often the products of combinatorial chemistry and high-throughput screening that favour potent, lipophilic targets. For these compounds, a dissolution profile alone is a poor predictor of what happens in a patient, because the rate-limiting step may not be how fast the tablet breaks apart but how fast the dissolved molecules squeeze through the lipid barriers of the intestinal wall.

Commercial dissolution-permeation systems do exist, and they have become valuable tools for formulation screening. Yet the Latvian team, led by Andrejs Sitovs and Valentyn Mohylyuk, identified three persistent shortcomings. The acceptor compartments of commercially available systems that include compendial dissolution testing hold no more than 50 millilitres, a volume that quickly saturates when a poorly soluble drug finally dissolves and needs somewhere to go. None of the existing platforms is compatible with ex vivo membranes, such as excised segments of animal or human intestine, which would allow active and facilitated transport mechanisms to be studied. And the dissolution step in most devices is not the standardised, pharmacopoeial kind that regulators around the world already recognise. The researchers’ answer was to bolt a CHM1 Ussing chamber onto a compendial USP2 dissolution apparatus, connecting the two with silicone tubing and a six-channel peristaltic pump in a closed circulation loop.

The engineering of the setup is elegantly straightforward. Two one-litre USP2 vessels ran side by side at 37 degrees Celsius with paddles spinning at 50 revolutions per minute. One vessel held the donor medium, a phosphate buffer at pH 6.8 that mimics the small intestinal lumen, where the tablet dissolved. The other held the acceptor medium, a phosphate buffer at pH 7.4, representing the blood side of the intestinal barrier. Medium was pumped from the donor vessel, roughly one centimetre below its surface, through the Ussing chamber, where it contacted a membrane mounted over a 1.13 square centimetre aperture, and then dripped passively back into the donor vessel from a height of about one centimetre. The acceptor vessel circulated through the opposite side of the chamber. Each tube ran one metre in length, and adhesive tape over the dissolution apparatus apertures kept evaporative losses to between 0.3 and 1.3 percent of the total volume over the course of an experiment.

The membrane at the heart of the chamber was an artificial lipid barrier modelled on the parallel artificial membrane permeability assay, better known in the field as PAMPA. The researchers spread 18.4 microlitres of soy L-α-phosphatidylcholine dissolved in dodecane, a mixture abbreviated LiDo, across one of two supporting filter membranes: a hydrophobic polyvinylidene fluoride membrane with 0.45 micrometre pores and a thickness of 125 micrometres, or a polycarbonate membrane with 0.20 micrometre pores and a thickness of only 10 micrometres. They tested LiDo concentrations of 5 and 10 percent by weight, deliberately lower than the 20 percent used in conventional PAMPA, because previous work had shown that increasing lecithin concentration in dodecane tends to slow naproxen permeation. Scanning electron microscopy confirmed clear differences in pore size and structure between the two filter materials, differences that would later prove consequential.

Naproxen itself was chosen with care. The drug, administered here as Nalgesin 550 milligram tablets containing naproxen sodium equivalent to 500 milligrams of naproxen, is a BCS class II compound: poorly soluble in acidic fluids but highly soluble at near-neutral pH, and transported across intestinal membranes purely by passive diffusion. That last property matters, because an artificial lipid membrane can only model passive transport. At the pH values of the small intestine, between 6.8 and 7.4, more than 99 percent of naproxen exists in its ionised, water-soluble form, according to the Henderson-Hasselbalch relationship. The researchers confirmed that proper sink conditions were maintained, with sink indices of 7.2 in the donor medium and 2.9 in the acceptor medium, meaning the buffers could hold far more dissolved drug than the experiments actually delivered. The tablets released more than half their payload within ten minutes and essentially the entire dose within thirty.

The permeability numbers that emerged were striking, and humbling. Across the 0.45 micrometre PVDF membrane, the apparent permeability coefficient of naproxen was 0.91 plus or minus 0.35 times ten to the minus eight centimetres per second with 5 percent LiDo, and 0.75 plus or minus 0.23 times ten to the minus eight with 10 percent LiDo, a difference that statistical analysis found not significant. The thinner polycarbonate membrane, however, roughly doubled the measured permeability, yielding 1.99 plus or minus 0.57 times ten to the minus eight centimetres per second at 5 percent LiDo. A control experiment in which donor and acceptor media were identical, both at pH 6.8, produced a similar value of 0.95 times ten to the minus eight, suggesting the pH gradient was not the dominant factor. Every one of these figures was approximately one hundred times lower than permeability values reported in the literature for naproxen, whether from artificial membrane-Ussing models, which report 19.55 times ten to the minus six centimetres per second, or from PAMPA experiments, which report around 4.2 times ten to the minus six.

The authors attribute this hundredfold gap primarily to the composition of their acceptor medium. Other studies routinely add chemical scavengers that mimic serum proteins, binding permeated drug and pulling the equilibrium forward, thereby inflating the apparent flux. The Latvian system used plain phosphate buffer with no such additives, so the acceptor side offered no extra thermodynamic incentive beyond the pH gradient. Membrane architecture likely played a supporting role: although the PVDF pores are on average 2.25 times larger than those of the polycarbonate filter, they appear structurally more complex under the microscope, which may affect how the lipid solution coats and distributes across the surface. The polycarbonate membrane is also twelve times thinner, shortening the diffusional path. Notably, electron microscopy showed the PVDF membrane used here matched the one in the commercial MicroFLUX system, meaning the discrepancy with published values cannot be blamed on a defective filter.

What the study delivers, then, is not a perfected predictive model but a validated platform with unusual flexibility. Because the permeation module is a standard Ussing chamber, the same rig can accept ex vivo tissue mounts, opening the door to dissolution-permeation experiments that capture active and facilitated transport, something no artificial membrane can do. The one-litre vessels provide large and adjustable acceptor volumes that poorly soluble compounds demand, and the dissolution step remains fully compendial, which matters for regulatory conversations. The researchers frame the potential payoff in broad terms: better bioavailability for oral formulations, fewer failed clinical trials, lower therapeutic doses, less unabsorbed drug excreted into the environment, and reduced financial risk across the development pipeline.

The work, funded through the European Union Recovery and Resilience Facility under a Latvian scientist grant for innovative biopharmaceutical evaluation of hard-to-develop oral medicines, is explicitly a feasibility study, and the authors are candid about its limits. The artificial membrane setup simulates passive transport only, and the permeability coefficients it generates are not yet calibrated against in vivo data. But the direction of travel is clear. If the methodology is adequately improved, as the team puts it, the humble dissolution paddle and the century-old Ussing chamber, working in tandem, could give formulation scientists a far more honest preview of how a new medicine will behave inside the human body, long before a single volunteer swallows the first tablet.

Subject of Research: A compendial dissolution-permeation system combining a USP2 dissolution apparatus with an Ussing chamber for biopharmaceutical evaluation of poorly soluble drugs

Article Title: Dissolution-permeation approach for biopharmaceutical evaluation: a feasibility study using naproxen

Article References: Sitovs, A., Gurkina, K., Petersone, L., & Mohylyuk, V. (2026). Dissolution-permeation approach for biopharmaceutical evaluation: a feasibility study using naproxen. Journal of Pharmacy & Pharmaceutical Sciences, 29, Article 16570. https://doi.org/10.3389/jpps.2026.16570

Image Credits: AI Generated

DOI: 10.3389/jpps.2026.16570

Keywords: dissolution-permeation, Ussing chamber, naproxen, BCS class II, biopharmaceutics, PAMPA, drug permeability, oral drug absorption, pharmaceutical analysis, LiDo membrane, sink conditions, in vitro testing

Nevirapine holds a special place in HIV medicine. It was the first non-nucleoside reverse transcriptase inhibitor, or NNRTI, approved by the United States Food and Drug Administration for the treatment of HIV-1 infection, and it remains a mainstay of combination therapy in many parts of the world. But the drug comes with baggage. Its toxicity profile includes serious dermatological reactions, Stevens-Johnson Syndrome and significant hepatotoxicity, and most nevirapine-based regimens require twice-daily dosing. That dosing burden, in part because drug levels cannot always be maintained sufficiently high, has contributed to the emergence of multi-drug resistant strains of HIV. To address these therapeutic shortcomings, researchers have proposed novel delivery systems, including niosomes, tiny surfactant-based vesicles stabilised with dicetyl phosphate and cholesterol, which the same research group previously developed using Span 20 or Span 80 surfactants.

Measuring a drug accurately across such diverse matrices, from crystalline bulk powder to lipid vesicles, demands a robust analytical method. Existing techniques for nevirapine include gradient elution, ion-pair reversed-phase HPLC, conventional isocratic HPLC, gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. Most were designed for plasma or dosage form analysis and suffer from long run times that make them poorly suited to routine quality control laboratories, where large numbers of samples must be processed quickly. Worse, many were developed by the one-factor-at-a-time approach, in which a single variable is adjusted while everything else is held constant. This strategy requires a large set of experiments and, critically, cannot reveal how factors interact with one another, potentially compromising the optimisation process.

The AQbD philosophy turns method development on its head. Rather than stumbling toward a workable separation, the analyst first identifies the critical analytical attributes that define success and the method parameters that influence them, then uses science- and risk-based understanding to build a defensible design space within which the method reliably performs. The cornerstone of this approach is design of experiments, and the researchers chose one of its most powerful tools: the Central Composite Design. This second-order design allows five levels of each input factor to be evaluated with far fewer experiments than a three-level full factorial design would demand, while still capturing curvature and interaction effects in the response surface.

Three input parameters were judged significant in preliminary studies: mobile phase flow rate, the fraction of organic solvent, and column temperature. The responses monitored were the retention time of nevirapine and the resolution factor between nevirapine and carbamazepine, the internal standard chosen after candidates including efavirenz and tenofovir disoproxil fumarate were considered. Twenty experiments, run in randomised order and in triplicate to minimise bias, mapped the design space. Analysis of variance revealed that flow rate and organic solvent content dominated both responses, with F-values reaching 545 and 823 for retention time and 2,578 for the solvent effect on resolution, while column temperature was statistically negligible across the range explored. Quadratic terms confirmed measurable curvature, meaning the relationships were not strictly linear, and a modest interaction between flow rate and solvent composition was detected.

The chemistry behind these effects is intuitive. Increasing the organic solvent content weakens the hydrophobic interaction between nevirapine and the C18 stationary phase, shortening retention, while a higher flow rate simply sweeps the analyte through the column faster. Resolution, by contrast, decreased as either solvent fraction or flow rate rose, because faster elution leaves less time for the analyte and internal standard to separate. Numerical optimisation using a desirability function in Design-Expert software converged on a set-point of 1.0 mL/min flow, 57.5:42.5 acetonitrile-to-water, and 25 degrees Celsius. Experimental verification in five replicates delivered a nevirapine retention time of 4.10 minutes, carbamazepine at 6.7 minutes, and a resolution factor of 13, with prediction errors of under four percent against the model’s forecasts.

Validation followed ICH Q2 (R1) guidelines and covered the full battery of required parameters. The calibration curve was linear from 0.5 to 200 micrograms per millilitre with a correlation coefficient of 0.9994, an unusually wide range that spans both low-dose and high-concentration applications. Repeatability and intermediate precision both produced relative standard deviations well below the five percent acceptance criterion, with some concentrations showing variability of less than 0.05 percent. Accuracy experiments at low, medium and high levels recovered between 99.1 and 101.5 percent of the theoretical concentration, with bias under two percent. The limit of quantitation was 0.5 micrograms per millilitre, confirmed experimentally with a precision of 0.65 percent, and the limit of detection was set at 0.033 micrograms per millilitre by convention.

Specificity and stability-indicating capability were then put to the test. Chromatograms of blank mobile phase, standards and tablet extracts showed no interference at the analyte retention time, confirming that excipients in both commercial Aspen nevirapine 200 mg tablets and in-house 400 mg sustained-release tablets did not disturb the measurement. Forced degradation studies subjected nevirapine to eight hours of reflux at 90 degrees Celsius in 30 percent hydrogen peroxide, 0.1 M hydrochloric acid, 0.1 M sodium hydroxide, neutral water and intense light at 500 watts per square metre. Recovery fell to 84.7 percent under oxidative stress, 90.7 percent under acidic conditions and 87.3 percent under alkaline stress, while the drug remained essentially stable under neutral and photolytic conditions. Crucially, no degradation peaks appeared at the analyte retention time in any experiment, demonstrating that the method can distinguish intact nevirapine from its breakdown products.

Real-world application sealed the case. The commercial tablets assayed at 98.35 percent of label claim and the in-house sustained-release tablets at 99.13 percent, both comfortably within pharmacopoeial expectations. When applied to niosomes, the method quantified both free drug in the supernatant and entrapped drug released by destroying the vesicle pellet with n-propanol, yielding entrapment efficiencies of 96.8 percent for optimised Span 20 systems and 98.0 percent for Span 80 systems, with values of 92.4 to 94.1 percent even in cholesterol-containing formulations. Compared with published methods, most of which rely on laborious phosphate or acetate buffers that shorten column life, generate waste and complicate preparation, the buffer-free isocratic system offers clear advantages in cost, sustainability and throughput. The authors argue that the AQbD framework, by explicitly defining a design space in which the method tolerates small fluctuations in flow, temperature and solvent ratio, produces analytical procedures that are not merely validated once but robust by construction, a lesson with universal application for pharmaceutical laboratories worldwide.

Subject of Research: Development and validation of a stability-indicating RP-HPLC method using Analytical Quality by Design for quantifying nevirapine in bulk, tablet and niosome formulations

Article Title: The use of QbD for the development and validation of a stability-indicating RP-HPLC method for the quantitation of nevirapine in bulk, tablet and niosome formulations

Article References: Witika, B. A., & Walker, R. B. (2026). The use of QbD for the development and validation of a stability-indicating RP-HPLC method for the quantitation of nevirapine in bulk, tablet and niosome formulations. Frontiers in Analytical Science, 6, Article 1735125. https://doi.org/10.3389/frans.2026.1735125

Image Credits: AI Generated

DOI: 10.3389/frans.2026.1735125

Keywords: nevirapine, Analytical Quality by Design, RP-HPLC, Central Composite Design, response surface methodology, stability-indicating method, niosomes, HIV, pharmaceutical analysis, ICH Q2 validation, forced degradation, carbamazepine internal standard

The research, led by Jagdish V. Manwar of the Takshashila Institute of Pharmaceutical Education and Research in Washim, India, applies an approach known as Analytical Quality by Design, or AQbD. Rather than relying on trial-and-error tinkering to find workable chromatographic conditions, AQbD treats the analytical method itself like a manufactured product. The scientist first defines what the method must achieve, identifies the variables that most strongly influence performance, and then uses structured experiments and statistical models to map out a design space in which the method is guaranteed to work. This philosophy mirrors the Quality by Design principles that regulators already expect in pharmaceutical manufacturing, and it is increasingly being extended to the laboratory procedures that verify drug quality.

Bempedoic acid presents a genuinely interesting analytical puzzle. The molecule is an ATP-citrate lyase inhibitor, blocking a key enzyme in hepatic cholesterol biosynthesis, and its chemical structure includes a substituted aromatic ring with a tert-butyl group and a terminal carboxylic acid. That carboxylic acid has a pKa of roughly 4.5, which means its ionization state, and therefore its chromatographic behavior, changes dramatically with pH. In reversed-phase high-performance liquid chromatography on a C18 column, the drug is retained mainly through hydrophobic interactions between its aromatic portion and the alkyl chains of the stationary phase. When the mobile phase is acidic, at pH 2.5, the carboxyl group remains protonated and non-ionized, strengthening those hydrophobic interactions, sharpening the peak, and suppressing troublesome secondary interactions with residual silanol groups on the silica support. At higher pH, the molecule becomes ionized, retention drops, and peak tailing can appear.

To exploit this chemistry systematically, Manwar designed a 3² full factorial experiment examining two critical method parameters: the percentage of acetonitrile in the mobile phase, ranging from 30 to 40 percent, and the flow rate, ranging from 0.8 to 1.2 milliliters per minute. Three critical quality attributes were tracked across nine experimental runs: retention time, the number of theoretical plates as a measure of column efficiency, and the tailing factor as a measure of peak symmetry. The resulting data were fitted with second-order quadratic models using response surface methodology, allowing the researcher to visualize how each variable, and their interactions, shaped chromatographic performance across the entire experimental space rather than at a single arbitrary point.

The statistics told a clear story. The retention time model achieved a coefficient of determination of 0.97446, with an F-value of 48.31 and a p-value of 0.00158, confirming that flow rate was the dominant lever on how quickly the drug eluted. The theoretical plate model was even more impressive, explaining 99.7 percent of the variance in column efficiency with an F-value of 564.38. The tailing factor model was weaker, at R² of 0.78467, but this turned out to be good news rather than bad: peak symmetry stayed within acceptable limits, between 1.0 and 1.2, across all nine runs, meaning the method was inherently robust to small fluctuations in operating conditions. Pareto analysis confirmed that acetonitrile composition had the largest positive effect on column efficiency, while both variables had only minor influence on peak shape.

From this statistical landscape, one experimental run emerged as the winner. Batch BMP.1, corresponding to 30 percent acetonitrile in water adjusted to pH 2.5 with orthophosphoric acid, delivered at 0.8 milliliters per minute through a C18 column with ultraviolet detection at 276 nanometers, produced a retention time of approximately 3.42 minutes with nearly 7,900 theoretical plates and a tailing factor of about 1.20. The choice of 276 nanometers was itself deliberate: it matches the drug’s absorption maximum from aromatic π–π* transitions while avoiding interference from mobile phase components and degradation products that absorb more strongly at lower wavelengths. Notably, the 30 percent organic content is far below the 60 to 70 percent used in many reported methods, a choice that pays dividends later in the environmental assessment.

Validation followed the ICH Q2(R1) guidelines that govern analytical procedure testing worldwide, and the numbers are impressive. Linearity held across the range of 5 to 25 micrograms per milliliter with a correlation coefficient of 0.9993. Precision was tight, with relative standard deviations below 1.5 percent for both intra-day and inter-day measurements. Accuracy, confirmed by standard addition recovery studies at three concentration levels, ranged from 101.21 to 101.52 percent. The limits of detection and quantitation came in at 0.81 and 2.07 micrograms per milliliter respectively, sensitive enough for trace-level work. When the method was applied to a commercial tablet formulation, Bemdac 20 milligrams, it measured a drug content of 100.41 percent of the label claim with a relative standard deviation of just 0.71 percent, with no interference from tablet excipients.

Perhaps most compelling for regulators and manufacturers is the method’s stability-indicating capability. Forced degradation studies exposed bempedoic acid to oxidative stress with 3 percent hydrogen peroxide, acidic hydrolysis with 0.01 normal hydrochloric acid, and alkaline hydrolysis with 0.01 normal sodium hydroxide. The drug proved most vulnerable to oxidation, degrading by 93.30 percent, while acidic conditions caused 78.43 percent degradation and alkaline conditions only 18.83 percent. Crucially, in every case the chromatographic method cleanly resolved the remaining parent drug peak from the degradation products, which appeared at distinct retention times. This ability to distinguish intact drug from its breakdown products is exactly what stability testing under ICH guidelines demands, and it means the method can serve not just for routine quality control but for assessing how formulations age over time.

The final layer of the study is its environmental accounting, an increasingly important dimension of analytical chemistry. Using the Analytical Eco-Scale, which subtracts penalty points for solvent hazards, consumption, energy demand, and waste from a perfect score of 100, the method earned an 82, well above the threshold of 75 that signifies an excellent green procedure. The AGREEprep metric, which evaluates sample preparation against ten criteria derived from the principles of green analytical chemistry, returned a score of 0.38, reflecting moderate greenness typical of conventional reversed-phase methods that rely on organic solvents. The National Environmental Method Index pictogram confirmed that the method uses no persistent, bioaccumulative, or toxic chemicals, operates at a non-corrosive pH, and generates less than 50 grams of waste per analysis, with acetonitrile’s hazardous classification being the main deduction.

Taken together, the study demonstrates that rigorous statistics and environmental responsibility need not be competing goals. By systematically mapping the design space rather than guessing at optimal conditions, the method achieves fast, precise, stability-indicating analysis in under four minutes per run while keeping organic solvent use deliberately low. The author notes that photolytic and thermal degradation studies were outside the present scope and could extend the stability profile in future work, but the framework is ready for routine quality control of bempedoic acid tablets and adaptable to other formulations after appropriate validation. As green analytical chemistry moves from aspiration to expectation in pharmaceutical laboratories, this AQbD-guided approach offers a template for how the next generation of quality-control methods might be built: statistically grounded, regulatorily compliant, and environmentally self-aware.

Subject of Research: Development and greenness evaluation of an AQbD-optimized RP-HPLC method for quantifying bempedoic acid in pharmaceutical dosage forms

Article Title: AQbD-guided statistical optimization and multi-metric greenness evaluation of liquid chromatographic method for analysis of bempedoic acid in pharmaceutical dosage forms

Article References: Manwar, J. V. (2026). AQbD-guided statistical optimization and multi-metric greenness evaluation of liquid chromatographic method for analysis of bempedoic acid in pharmaceutical dosage forms. Discover Chemistry, 3(1), Article 580. https://doi.org/10.1007/s44371-026-01026-4

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01026-4

Keywords: bempedoic acid, AQbD, RP-HPLC, factorial design, green analytical chemistry, stability-indicating method, forced degradation, pharmaceutical analysis, Analytical Eco-Scale, AGREEprep, method validation, cholesterol

The use of density functional theory as a companion tool to electroanalysis reflects a broader trend in sensor development, where computational screening of molecular orbitals, charge distribution, and bond strengths can guide the interpretation of voltammetric peaks before extensive experimental optimization is undertaken. In the case of bepotastine, identifying the piperidine nitrogen as the electroactive site is chemically sensible, because tertiary amine groups in drug molecules commonly undergo electrochemical oxidation at carbon-based electrodes. The transfer of two electrons accompanied by a single proton suggests a concerted pathway in which the nitrogen center loses electron density while the proton balance is maintained by the surrounding buffer environment. Such mechanistic clarity has practical consequences: it informs the selection of operating pH, helps anticipate potential interferences from structurally related amines, and provides a foundation for extending the same sensing logic to other antihistaminic compounds that share similar piperidine or piperidine-like motifs.

Tungsten doping of vanadium dioxide deserves particular attention as a materials strategy. Vanadium dioxide is well known for its reversible metal-insulator transition, a property that has been exploited in switching devices, thermochromic coatings, and infrared sensing. When tungsten atoms are incorporated into the VO2 lattice, they act as electron donors and structural stabilizers, shifting the transition temperature and modifying the density of charge carriers available at the particle surface. For electrochemical sensing, this translates into a material with improved electrical conductivity and a greater number of electroactive sites per unit mass. The nanoparticles used in the study, with dimensions in the range of zero to fifty nanometers, present a high surface-to-volume ratio, which multiplies the contact area between the analyte and the sensing layer. Drop-casting a dilute suspension of these nanoparticles onto the printed carbon electrode, repeated twice to ensure an even coating, is a simple yet effective deposition route that avoids the need for sophisticated cleanroom equipment and keeps the fabrication process accessible to laboratories with modest infrastructure.

The screen-printed carbon electrode format itself is central to the green chemistry argument advanced by the authors. Conventional analytical methods for bepotastine have relied predominantly on chromatographic separation, which, while accurate and well established, demands significant quantities of organic solvents, specialized columns, and trained personnel. Sample preparation schemes for chromatography can be lengthy, and the associated solvent consumption poses both environmental and economic burdens, particularly when large numbers of samples must be processed. Electrochemical sensing with disposable printed electrodes inverts this equation. The measuring cell consumes microliter volumes of sample, the electrodes are mass-producible at low cost, and the instrumentation required is comparatively compact and affordable. The home-made printing ink described in the experimental section, built from graphite powder, conductive carbon black, ethyl cellulose, and a polyurethane binder dissolved in a terpineol, ethanol, and acetone solvent blend, illustrates how functional sensors can be formulated from widely available materials without resorting to exotic or hazardous reagents.

The analytical performance figures reported for the W-VO2 nanoparticle modified sensors are competitive with, and in several respects superior to, previously described methods for bepotastine quantification. A linear dynamic range extending from 0.02 to 3.65 micrograms per milliliter covers the concentration window relevant to pharmaceutical quality control, where tablet and ophthalmic formulations must be assayed for content uniformity and potency. The limit of detection of 0.006 micrograms per milliliter indicates sensitivity sufficient to monitor trace residues, which is valuable not only for formulation analysis but also for the detection of low-level impurities or degradation products that could compromise patient safety. The validation of the differential pulse voltammetric method across the standard parameters of accuracy, precision, linearity, specificity, stability, and reproducibility follows internationally recognized expectations for analytical method development, lending credibility to the claim that the platform is suitable for routine deployment rather than merely a laboratory demonstration.

The demonstration of the sensor in real and simulated matrices strengthens its practical relevance. Pharmaceutical tablets and ophthalmic formulations represent the primary products in which bepotastine besilate is marketed, and assaying these directly, without extensive pretreatment, showcases the robustness of the electrochemical approach against formulation excipients. The use of synthetic aqueous humor as a biological surrogate is particularly thoughtful, because bepotastine is administered topically for allergic conjunctivitis, and the tear film is the biological fluid most directly relevant to its therapeutic action. Non-invasive monitoring in ocular fluids is an attractive concept for pharmacokinetic and therapeutic drug monitoring studies, and a disposable printed electrode modified with a stable metal oxide nanoparticle layer offers a plausible route toward such applications in resource-limited clinical settings where chromatographic facilities are unavailable.

The additional reporting of degradation behavior and dissolution profiles for bepotastine in pharmaceutical tablets adds a formulation science dimension to the analytical work. Dissolution testing is a cornerstone of solid oral dosage form evaluation, because the rate at which a drug is released from its tablet matrix governs its bioavailability and therapeutic onset. Degradation studies, meanwhile, are mandated by stability testing guidelines to establish how a drug responds to stress conditions such as heat, light, oxidation, and hydrolysis. The observation that the stock bepotastine solution was kept in the dark to avoid photocatalytic degradation hints at the drug’s susceptibility to light-induced breakdown, a property that the electrochemical sensor could potentially exploit for monitoring photodegradation pathways in real time. Integrating sensing with dissolution and stability assessment within a single analytical framework is an efficient approach that reduces the overall experimental burden on quality control laboratories.

Electrochemical impedance spectroscopy played a complementary role in characterizing the modified electrodes, providing insight into the charge transfer resistance at the electrode-solution interface. The use of a ferricyanide and potassium chloride solution for these measurements is a standard practice, since the reversible ferricyanide couple serves as a sensitive probe of interfacial kinetics. A decrease in charge transfer resistance after modification with the tungsten-doped vanadium dioxide nanoparticles would confirm that the sensing layer enhances electron transport, consistent with the conductive character imparted by tungsten doping. Cyclic voltammetry, in turn, allowed the authors to map the pH dependence of the bepotastine oxidation peak and to establish the scan rate relationships that underpin the mechanistic assignment of the one proton and two electron pathway. The combination of SEM and EDX characterization verified that the nanoparticles were uniformly distributed across the printed electrode surface and that the elemental signature of tungsten and vanadium was present as intended, ruling out concerns about incomplete or heterogeneous modification.

The selectivity assessment of the W-VO2 nanoparticle sensors against potential interferents is critical for their intended use in pharmaceutical and biological matrices. Formulations commonly contain excipients such as binders, colorants, and preservatives, while biological fluids contain ascorbate, urate, and a variety of endogenous amines that can be electroactive at carbon electrodes. The reported adequate selectivity suggests that the operating pH and the nanoparticle sensing layer jointly suppress responses from these species, preserving the integrity of the bepotastine signal. Mechanical stability, measurement reproducibility, and prolonged storage lifetime are additional attributes that determine whether a sensor can transition from a research prototype to a practical quality control tool. Disposable printed electrodes modified with a stable metal oxide layer are inherently suited to single-use deployment, which eliminates electrode fouling concerns between measurements and simplifies standardization across laboratories.

Looking at the broader context of sustainable analytical chemistry, the study aligns with the priorities of the US Green Chemistry Program by emphasizing reagent safety, energy efficiency, waste reduction, and miniaturization. The greenness of an analytical method is increasingly evaluated through formal assessment tools that score solvent hazard, energy consumption, and sample throughput, and electrochemical sensing with printed electrodes generally performs favorably under such metrics. The vanadium-derived electrode materials combine low fabrication cost with safety and strong electrochemical metrics, making them an appealing alternative to more expensive noble metal modifiers such as gold or platinum nanoparticles. As regulatory expectations around environmental sustainability in pharmaceutical analysis continue to tighten, methods of this kind are likely to see growing adoption, particularly for routine content uniformity testing, stability monitoring, and point-of-need drug quantification where speed, simplicity, and minimal environmental footprint are paramount considerations.

The convergence of computational mechanistic insight, nanomaterials engineering, and green analytical chemistry in this work illustrates how modern sensor development has become a genuinely multidisciplinary endeavor. The tungsten-doped vanadium dioxide nanoparticles serve as the enabling material, the screen-printed carbon electrode provides the sustainable and disposable platform, and the density functional theory calculations supply the molecular-level understanding that connects the observed voltammetric behavior to the structure of the drug. Together, these elements produce a sensing system that is not only sensitive and selective but also interpretable, reproducible, and environmentally considerate, qualities that position it well for integration into routine pharmaceutical quality control and for future extension toward non-invasive human health monitoring in clinical and field settings.

Subject of Research: Green electrochemical sensing of bepotastine besilate using tungsten-doped vanadium dioxide nanoparticles with DFT mechanistic analysis

Article Title: First report on green electrochemical sensing of bepotastine besilate based on tungsten doped vanadium dioxide nanoparticles: DFT assisted mechanistic insight

Article References: Alhawiti, A. S., Alharbi, B. H., Alhifthi, A., Alfadhli, S., Jawhari, A. H., Snari, R. M., Bahamran, A. A., & El-Metwaly, N. M. (2026). First report on green electrochemical sensing of bepotastine besilate based on tungsten doped vanadium dioxide nanoparticles: DFT assisted mechanistic insight. Journal of Saudi Chemical Society, 30(6), Article 78. https://doi.org/10.1007/s44442-026-00131-4

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00131-4

Keywords: bepotastine besilate, electrochemical sensor, vanadium dioxide, tungsten doping, screen-printed electrode, voltammetry, green analytical chemistry, DFT, antihistamine, pharmaceutical analysis, First, report

The two active ingredients occupy distinct pharmacological territories. Brexpiprazole, chemically 7-[4-[4-(1-benzothiophen-4-yl)piperazin-1-yl]butoxy]-1H-quinolin-2-one, is an atypical antipsychotic classified as a serotonin-dopamine activity modulator. It partially activates D2 dopamine and serotonin 1A receptors and binds strongly to serotonin, dopamine, and alpha-adrenergic receptors; the United States Food and Drug Administration approved it on July 10, 2015. Escitalopram oxalate, structurally (1S)-1-[3-(dimethylamino)propyl]-1-(4-fluorophenyl)-3H-2-benzofuran-5-carbonitrile oxalate, belongs to the selective serotonin reuptake inhibitor class and treats depression and anxiety by increasing serotonergic activity in the brain. The combination of the two agents was approved in 2014 and has been studied in clinical trials for mood disorders, which makes reliable analytical tools for the pair increasingly important.

To build the method, the team used a Shimadzu semi-automatic liquid chromatograph equipped with a photodiode array detector and Win Chrome software, injecting samples through a microliter syringe onto a reversed-phase C18 column measuring 250 millimeters by 4.6 millimeters with five-micron particles. Raw materials were supplied as gift samples by Virdev Pharma of Palsana and Sun Pharmaceutical Industries of Panoli, and the researchers prepared a synthetic mixture mimicking a combined dosage form at a ratio of 40 micrograms per milliliter of brexpiprazole to 120 micrograms per milliliter of escitalopram oxalate. Because no commercial product exists, the synthetic mixture served as the practical test bed for the entire validation exercise.

Optimization of the chromatographic conditions revealed that a mobile phase of methanol and phosphate buffer, adjusted to pH 4.0 with orthophosphoric acid and mixed in a 55:45 volume ratio, delivered the best performance. Elution ran in isocratic mode at a flow rate of one milliliter per minute, with detection at 214 nanometers and a total run time of ten minutes. Under these conditions brexpiprazole eluted at 2.7 minutes and escitalopram at 7.0 minutes in the reported system suitability work, with symmetrical peak shapes, theoretical plate counts above 2000, and tailing factors at or below 2.0. The separation logic is rooted in the chemistry of the two molecules: both carry basic functional groups and exist predominantly in protonated form at pH 4.0, but brexpiprazole is considerably more lipophilic, with a log P of roughly 4.7 to 5.0 compared with 3.5 to 4.0 for escitalopram. That difference governs how strongly each analyte interacts with the nonpolar C18 stationary phase and therefore dictates the elution order.

Validation followed the International Council for Harmonization guideline Q2(R2), the current global standard for analytical procedure validation. Linearity was assessed at five concentration levels with six replicates each, spanning 0.5 to 3 micrograms per milliliter for brexpiprazole and 5 to 30 micrograms per milliliter for escitalopram oxalate. Calibration curves returned correlation coefficients exceeding 0.999 for both drugs, indicating an exceptionally straight relationship between peak area and concentration across the working ranges. Accuracy was confirmed through standard addition and recovery studies at 80, 100, and 120 percent spiking levels, with satisfactory recoveries demonstrating that common formulation excipients do not interfere with quantification.

Precision, the method’s ability to produce consistent results, was evaluated in both intraday and interday experiments. Three standard solutions of different concentrations were injected repeatedly within a single day and again across three consecutive days, and the relative standard deviation stayed below 2.0 percent throughout. Specificity was demonstrated by analyzing blank mobile phase and sample solutions, with no interfering peaks appearing at the retention times of either analyte. Sensitivity limits were calculated from the standard deviation of the response and the slope of the calibration curve using the ICH equations LOD equals 3.3 times sigma over S and LOQ equals 10 times sigma over S, yielding low detection and quantification limits that confirm the method’s suitability for trace-level work. Robustness testing deliberately introduced small variations in flow rate, mobile phase composition, pH, and detection wavelength, while ruggedness was probed through changes of analyst and column, with retention times remaining stable in all cases.

When the optimized method was applied to the synthetic mixture containing 2 micrograms per milliliter of brexpiprazole and 20 micrograms per milliliter of escitalopram oxalate, the assay results were striking: 99.67 percent recovery for brexpiprazole with a relative standard deviation of 0.308 percent, and 99.94 percent for escitalopram oxalate with a relative standard deviation of 0.227 percent. These figures indicate that the procedure measures the actual content of a mixture with near-perfect fidelity and minimal scatter, exactly the profile a quality control laboratory needs when certifying batches of a finished product.

What distinguishes this study from a routine validation exercise is its systematic greenness assessment. The authors evaluated the method with three complementary tools drawn from Green Analytical Chemistry. The AGREE metric, which scores a procedure against the twelve principles of green analytical chemistry, returned 0.71, indicating good compliance. The Blue Applicability Grade Index, which weighs practical applicability alongside sustainability, scored 72.5, and the Complex GAPI pictogram, which accounts for reagent hazards, energy consumption, and waste generation across the whole procedure, scored 81. The environmental arithmetic is straightforward: each ten-minute analysis consumes roughly ten milliliters of mobile phase, split into 5.5 milliliters of methanol and 4.5 milliliters of water, and generates only about ten milliliters of waste. The simple methanol-water system avoids more hazardous solvents entirely, and the short run time keeps energy demand low.

The team also extended the evaluation into White Analytical Chemistry, a framework that mirrors the twelve green principles but adds two further pillars: red for analytical performance and blue for practical and economic factors. By reporting the arithmetic means for the red, green, and blue sections separately, the authors acknowledged that a truly sustainable method must be green without sacrificing accuracy, precision, or cost-effectiveness. Their conclusion was that the method is acceptably green and suitable for sustainable routine applications without compromising performance, with only minor limitations remaining.

The practical significance of the work lies in its readiness for routine use. Because the method is the first created for rapid analysis of this binary mixture at a single wavelength, and because it passed every ICH Q2(R2) validation parameter with strong margins, pharmaceutical laboratories could adopt it directly for stability studies, formulation development, and batch release testing of any future brexpiprazole-escitalopram combination product. The combination of a ten-minute run time, modest solvent consumption, sub-2-percent variability, and recoveries near 100 percent represents a template for how modern analytical chemistry can serve drug development while shrinking its own environmental footprint, a balance that regulators and manufacturers alike are increasingly demanding.

Subject of Research: Development and greenness assessment of a validated RP-HPLC method for simultaneous estimation of brexpiprazole and escitalopram oxalate

Article Title: Development, validation, and greenness assessment of a green RP-HPLC method for rapid simultaneous estimation of brexpiprazole and escitalopram oxalate in combined dosage form

Article References: Solanki, D., & Dedania, Z. (2026). Development, validation, and greenness assessment of a green RP-HPLC method for rapid simultaneous estimation of brexpiprazole and escitalopram oxalate in combined dosage form. Discover Chemistry, 3(1), Article 444. https://doi.org/10.1007/s44371-026-00887-z

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00887-z

Keywords: RP-HPLC, brexpiprazole, escitalopram oxalate, method validation, ICH Q2(R2), green analytical chemistry, AGREE metric, pharmaceutical analysis, liquid chromatography, antidepressants, quality control, sustainable chemistry

The two drugs involved work in strikingly different ways. Escitalopram oxalate belongs to the selective serotonin reuptake inhibitor (SSRI) family, a class that raises serotonin levels in the brain by blocking its reabsorption, thereby strengthening serotonergic signaling. It is widely prescribed for depression and anxiety because of its high tolerability and selectivity. Bupropion hydrochloride, by contrast, is an atypical antidepressant classified as a norepinephrine–dopamine reuptake inhibitor, or NDRI. By preventing the reuptake of norepinephrine and dopamine, it boosts extracellular levels of these monoamine neurotransmitters and increases noradrenergic and dopaminergic neurotransmission, ultimately raising postsynaptic neuronal activity. The fixed-dose combination of the two was approved in April 2017 and has since been used to manage mood disorders, offering clinicians a way to target multiple neurotransmitter systems at once.

Measuring both compounds in one tablet, however, is not trivial. The two molecules differ in polarity, concentration ratio, and chemical behavior, and a synthetic tablet typically contains a large excess of bupropion relative to escitalopram. In the new method, the researchers dissolved a quantity of synthetic mixture equivalent to 10 milligrams of escitalopram and 150 milligrams of bupropion in methanol, sonicated it for 15 to 20 minutes to ensure complete extraction, filtered the solution through a 0.45-micrometer membrane, and diluted it to yield a final sample containing 1 microgram per milliliter of escitalopram and 15 micrograms per milliliter of bupropion. That 1:15 ratio is a demanding test for any chromatographic method, because the detector must remain linear across very different concentration ranges for the two analytes.

The chromatographic conditions the team settled on are elegantly simple. Separation was achieved on a C18 column measuring 250 by 4.6 millimeters with 5-micrometer particles, using a mobile phase of acetonitrile and phosphate buffer at pH 3, adjusted with orthophosphoric acid, in a 75:25 volume ratio. The system ran under isocratic elution, meaning the solvent composition stays constant throughout the run, at a flow rate of 1.0 milliliter per minute with a 10-microliter injection volume and detection at 233 nanometers using a photodiode array detector. The column temperature was held at 30 degrees Celsius. Under these conditions, escitalopram eluted first, at about 4.2 minutes, followed by bupropion at about 7.7 minutes. The order makes physical sense: the more polar escitalopram has a stronger affinity for the polar mobile phase and spends less time interacting with the non-polar stationary phase, while the less polar bupropion lingers longer on the hydrophobic C18 surface before washing off.

Reaching that clean separation took systematic optimization. The researchers experimented with different solvents, pH levels, and solvent compositions before landing on the acidic acetonitrile–buffer blend. Ultraviolet spectra of both drugs were recorded between 200 and 400 nanometers to choose a wavelength at which both compounds absorb strongly enough for simultaneous detection, and 233 nanometers emerged as the best compromise. The resulting chromatograms showed well-resolved, symmetrical peaks without significant tailing, and system suitability testing confirmed healthy values for resolution, tailing factor, and theoretical plates, the classic metrics chromatographers use to judge whether a system is performing properly before trusting any data it produces.

Validation followed the international ICH Q2(R1) guideline, the industry standard for analytical procedure validation. Linearity was demonstrated for escitalopram across 1 to 6 micrograms per milliliter and for bupropion across 15 to 90 micrograms per milliliter, with correlation coefficients of 0.999 in both cases, meaning the detector response rose almost perfectly in proportion to concentration. Accuracy, assessed through recovery experiments, ranged from 98.51 to 100.33 percent for escitalopram and 99.05 to 100.23 percent for bupropion, figures comfortably within the narrow windows regulators expect. Precision was evaluated as repeatability, intraday, and interday variability expressed as relative standard deviation, and all values came in below 2 percent, indicating the method produces consistent results regardless of when or how the measurements are made within a day or across days.

The method also proved sensitive enough for its purpose. Limits of detection, calculated using the ICH equations LOD = 3.3σ/S and LOQ = 10σ/S, where σ is the standard deviation of the response and S the slope of the calibration curve, came out at 0.101 micrograms per milliliter for escitalopram and 1.188 micrograms per milliliter for bupropion. The corresponding limits of quantification were 0.308 and 3.602 micrograms per milliliter, respectively. Specificity testing added another layer of confidence: when blank solutions were analyzed, no interfering peaks appeared at the retention times of either drug, showing that common tablet excipients would not distort the results. Robustness and ruggedness studies, in which chromatographic conditions were deliberately varied, confirmed that retention times and peak areas held steady, meaning the method tolerates small everyday fluctuations in a quality-control laboratory.

When the team applied the method to a synthetic mixture containing 10 milligrams of escitalopram and 150 milligrams of bupropion, the assay recovered 99.98 percent of the escitalopram and 99.94 percent of the bupropion. That near-perfect recovery, combined with the confirmation that additives in the mixture did not disrupt the analysis, demonstrates that the approach is ready for real-world formulation testing. The authors note that the method offers simple chromatographic conditions, rapid analysis, and simultaneous estimation of both drugs at a single wavelength, a combination that translates directly into lower costs and faster turnaround times for pharmaceutical quality-control labs that must analyze thousands of samples.

Why does this matter beyond the laboratory bench? Fixed-dose combination antidepressants sit at the intersection of pharmacology and manufacturing, and every batch that reaches patients depends on validated analytical methods like this one. The literature already contains numerous chromatographic techniques for bupropion and escitalopram individually or paired with other drugs such as clonazepam, etizolam, naltrexone, or aripiprazole, but each new approved combination demands its own validated method tuned to the specific ratio and properties of the drugs involved. By providing a straightforward, reproducible RP-HPLC procedure validated to ICH standards for the escitalopram–bupropion pair, Solanki and Dedania have given manufacturers and regulators a practical tool for routine quality control. It is a reminder that behind every psychiatric prescription lies a web of unglamorous but essential chemistry, ensuring that the pill in the bottle delivers precisely what the label promises.

Subject of Research: Development and validation of an RP-HPLC method for simultaneous quantification of escitalopram oxalate and bupropion hydrochloride in pharmaceutical formulations

Article Title: RP-HPLC method for the simultaneous estimation of escitalopram oxalate and bupropion hydrochloride used for treatment of mood disorder

Article References: Solanki, D., & Dedania, Z. (2026). RP-HPLC method for the simultaneous estimation of escitalopram oxalate and bupropion hydrochloride used for treatment of mood disorder. Discover Chemistry, 3(1), Article 576. https://doi.org/10.1007/s44371-026-01025-5

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01025-5

Keywords: RP-HPLC, escitalopram oxalate, bupropion hydrochloride, method validation, ICH guidelines, antidepressants, mood disorders, pharmaceutical analysis, quality control, chromatography, SSRI, NDRI

The technique at the heart of the work is reverse-phase high-performance liquid chromatography, or RP-HPLC, a workhorse of pharmaceutical quality control. In essence, the method pushes a dissolved sample through a narrow column packed with microscopic silica beads coated in a nonpolar layer. The drug molecules interact with this stationary phase while being carried along by a liquid mobile phase, and because different compounds interact with different strengths, they separate and emerge at distinct times. A detector then registers each compound as a peak, and the size of the paracetamol peak reveals how much of the drug is present. The sensitivity, precision, and reproducibility of RP-HPLC have made it the default choice for verifying the content of pharmaceutical formulations, including the ubiquitous paracetamol tablet.

What makes the new study notable is not the mere existence of another paracetamol assay, as the authors themselves acknowledge, but the systematic way the method was constructed. Conventional method development typically proceeds one variable at a time: adjust the solvent mixture, run the sample, adjust the pH, run it again. This trial-and-error process is slow, and worse, it can miss interactions between variables, situations where changing two parameters together produces effects that neither produces alone. Analytical Quality by Design, or AQbD, flips the script. It begins with an Analytical Target Profile, a formal statement of what the method must achieve, and then uses risk assessment and designed experiments to map out how every critical parameter influences performance. The result is not just a working method but a deep, quantitative understanding of why it works.

The researchers, led by Kranti Satpute of Dayanand College of Pharmacy in Latur, Maharashtra, began by defining the attributes their method needed: adequate retention of the paracetamol peak, good peak symmetry, high chromatographic efficiency, a reproducible signal, and clean separation from any tablet excipients or impurities. They then ranked potential method variables by risk, classifying each as low, medium, or high priority. This triage focused their experimental effort on the parameters most likely to disrupt the analysis, a philosophy borrowed directly from quality risk management frameworks used across the pharmaceutical industry. Variables deemed low risk, such as those unlikely to affect retention or peak shape, were set aside, while high-risk candidates were earmarked for systematic investigation.

For the optimization itself, the team turned to a Central Composite Design, a form of Response Surface Methodology that examines multiple factors simultaneously across five levels each. Three chromatographic parameters were varied: the concentration of organic modifier in the mobile phase, the pH of that phase, and the flow rate of the pump. The ranges, spanning 5 to 25 percent organic modifier, pH 6.3 to 6.7, and flow rates of 0.8 to 1.2 milliliters per minute, were grounded in preliminary experiments. The design tracked three responses: retention time, peak area, and theoretical plate count, the last being a measure of column efficiency. Analysis of variance then revealed which factors and interactions were statistically significant, something a one-factor-at-a-time approach could never expose.

The statistics delivered a clear verdict. Retention time was strongly influenced by organic modifier concentration, with a p-value of 0.0001, and by flow rate, at p equal to 0.0004, while pH turned out to be statistically irrelevant to retention, with a p-value of 0.9917. Flow rate also significantly affected peak area and theoretical plate count. Three-dimensional response surface plots visualized these relationships, showing retention time falling as organic modifier increased while peak area and plate counts remained comparatively stable across the studied ranges. This kind of visual and statistical map of method behavior is precisely the knowledge that conventional approaches leave on the table, and it gave the team a rational basis for deciding which parameters must be tightly controlled during routine use.

The final method settled on a mobile phase of water, acetonitrile, and methanol in an 80:15:5 ratio, adjusted to pH 6.5 with triethylamine, flowing at 1.0 milliliter per minute through an Agilent TC-C18 column, with ultraviolet detection at 254 nanometers, the wavelength where paracetamol absorbs most strongly. Under these conditions, paracetamol eluted as a sharp, symmetrical peak at roughly 5.4 minutes, within a total run time of just seven minutes. Crucially, the design of experiments also defined a Method Operable Design Region, a design space within which the method is guaranteed to perform acceptably even if conditions drift slightly. Instead of a single fragile set of settings, quality control laboratories gain a flexible operating window with assured performance, a concept regulators increasingly favor under ICH Q14.

Validation followed the latest ICH Q2(R2) guidelines, and the numbers were impressive. Linearity held across concentrations from 18 to 42 micrograms per milliliter with a correlation coefficient of 0.9995, about as close to a perfect straight line as analytical chemistry allows. Repeatability produced a relative standard deviation of just 0.66 percent, and intermediate precision, tested across different days, analysts, and instruments, came in at 1.75 percent. Accuracy experiments at 80, 100, and 120 percent of the target concentration yielded recoveries between 100.03 and 102.85 percent, with an overall mean recovery of 101.58 percent and a relative standard deviation of 0.70 percent, comfortably within the accepted 97 to 103 percent window. Specificity testing confirmed that blank, placebo, and impurity-spiked samples produced no interfering peaks at the paracetamol retention time, and photodiode array assessment supported peak purity.

Robustness testing added a final layer of confidence, showing that the method tolerated small deliberate variations in conditions within the established design space, though the authors caution that flow rate and organic modifier concentration deserve strict control given their outsized influence on retention. An updated risk assessment confirmed that controls such as instrument calibration and proper material handling had reduced residual risks to a minimum. The practical upshot is a method that is simple, fast, accurate, and, perhaps most importantly, self-documenting: a laboratory adopting it inherits not just a recipe but a scientifically justified understanding of which knobs matter and how much they can be turned. For a drug taken by hundreds of millions of people daily, that transparency is more than academic elegance.

The broader significance of the study lies in its demonstration of a lifecycle mindset for analytical procedures. Rather than treating method development as a one-off exercise capped by a validation report, the AQbD framework embeds risk management, multivariate statistics, and control strategies into the very fabric of the method, aligning with the quality-by-design principles now sweeping through pharmaceutical manufacturing. As regulators worldwide push for analytical flexibility backed by scientific justification, studies like this one, applying Central Composite Design to an everyday drug, show how even the most routine quality control test can be rebuilt as a model of modern, data-driven science. The humble paracetamol tablet, it turns out, is a fitting stage for that quiet revolution.

Subject of Research: Development and validation of an AQbD-based RP-HPLC method for quantifying paracetamol in pharmaceutical tablets

Article Title: Analytical quality by design driven RP HPLC method development and validation for quantification of paracetamol in pharmaceutical tablets

Article References: Satpute, K., Avhad, A., Syed, S. M., Sonwane, S., Yelmate, A., Shetkar, B., Birajdar, M., & Lohiya, G. (2026). Analytical quality by design driven RP HPLC method development and validation for quantification of paracetamol in pharmaceutical tablets. Discover Chemistry, 3(1), Article 565. https://doi.org/10.1007/s44371-026-01007-7

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01007-7

Keywords: paracetamol, RP-HPLC, Analytical Quality by Design, Central Composite Design, method validation, pharmaceutical analysis, liquid chromatography, ICH Q2(R2), design space, quality control, response surface methodology, tablets

The analytical challenge is more subtle than it might first appear. Most existing methods for baricitinib were developed for bulk powder, tablets, or blood plasma. Each of those matrices is comparatively forgiving. A transdermal nano-formulation, by contrast, is a chemical jungle: polymers, adhesives, permeation enhancers, and nano-carrier excipients all crowd the chromatogram, and any of them can co-elute with the drug and corrupt the result. Diffusion experiments add another layer of difficulty, because receptor fluid samples collected over many hours contain low drug concentrations that demand sensitivity, and repeated sampling demands stability. Spectrophotometric approaches lack the sensitivity for these dilute samples, while LC-MS/MS methods, though exquisitely sensitive, require expensive instrumentation and complex sample preparation that few quality control laboratories can justify for routine release testing. The Hyderabad team set out to fill that gap with a method that is simple, cheap, and robust enough for everyday use.

The heart of the method is an unusual choice of stationary phase. Baricitinib is a moderately polar molecule studded with hydrogen bond donors and acceptors, and on conventional C18 columns those features tend to interact with residual silanol groups on the silica surface, producing peak tailing and erratic retention. During preliminary experiments, the researchers found exactly that behavior. Their solution was the Phenomenex Synergi Polar-RP column, which embeds a polar group within the alkyl chain of the stationary phase. This polar-embedded design shields the analyte from unwanted silanol interactions and improves selectivity for moderately polar compounds, yielding sharper, more symmetrical peaks and better retention control, particularly under the aqueous-rich mobile phase conditions the method requires. The 80 angstrom pore size and 150 millimeter column length struck an optimal balance between efficiency and analysis time.

The mobile phase was tuned with equal care. The final system pairs 10 millimolar potassium dihydrogen phosphate buffer at pH 3.0 with acetonitrile in a 70:30 ratio, run isocratically at 1.0 milliliter per minute on an Agilent 1260 Infinity II system with diode array detection at 254 nanometers. The acidic pH is not arbitrary: it holds baricitinib in a consistent ionization state and suppresses the ionization of residual silanol groups, both of which sharpen the peak and improve reproducibility. Acetonitrile won out over methanol after direct comparison, offering stronger elution strength, lower viscosity, reduced backpressure, and crucially lower UV absorbance at the detection wavelength, which produced a stable baseline and better sensitivity. Under these conditions baricitinib elutes at almost exactly 5 minutes, with theoretical plate counts of 5402 for assay samples and 9657 for diffusion samples and tailing factors near 1.05, indicating excellent column efficiency and near-ideal peak symmetry in both matrices.

Validation followed the International Council for Harmonisation Q2(R2) guidelines, the global benchmark for analytical method performance. For the assay of the finished nano-formulation, the method proved linear from 12 to 100 micrograms per milliliter with a correlation coefficient of 0.999. Recovery studies, in which known quantities of drug were spiked into pre-analyzed formulation matrix at three levels, returned mean recoveries between 98.14 and 100.56 percent, confirming that the methanol-based extraction, which involves an hour of sonication with intermittent agitation, pulls the drug out of the nano-carrier matrix completely and without degradation. Intra-day and inter-day precision both produced relative standard deviations below 2 percent, and peak purity analysis confirmed that no excipient interfered at the analyte’s retention time. The assay of the actual transdermal nano-formulation came in at 99.8 plus or minus 0.15 percent drug content, a result that speaks to both the uniformity of the formulation and the accuracy of the measurement.

For the Franz diffusion application, the team revalidated the method in the diffusion matrix, where samples are drawn from receptor fluid rather than extracted from the formulation. Calibration was linear from 5 to 75 micrograms per milliliter, again with a correlation coefficient of 0.999, and recoveries ranged from 99.36 to 100.83 percent. The diluent for this variant is simply the dissolution medium itself, pH 7.4 phosphate buffer containing 0.5 percent Tween 80, which eliminates an extra sample preparation step and reduces the chance of error. Robustness testing, which deliberately perturbs flow rate, organic phase composition, and detection wavelength, showed no meaningful impact on retention time, plate count, or tailing factor. Solution stability studies demonstrated that both standards and samples remain stable for 24 hours at bench-top conditions and up to 48 hours refrigerated at 2 to 8 degrees Celsius, a practical boon for laboratories that batch-process diffusion samples collected across a full day of experiments.

With the analytical platform secured, the researchers turned it loose on the question that matters most for a transdermal product: how does the drug actually move? Using a Franz diffusion cell with a 10 milliliter receptor compartment, a 1 square centimeter effective diffusion area, and a pretreated Strat-M membrane held at 37 degrees Celsius, they sampled at 0.5, 1, 2, 4, 6, 12, and 24 hours, replacing each withdrawn aliquot with fresh medium to maintain sink conditions. The cumulative permeation data showed a controlled and sustained release profile stretching across the full 24-hour window, with drug crossing the membrane at a steady, predictable rate rather than dumping in an initial burst. For a once-daily anti-inflammatory that currently relies on oral dosing, a formulation capable of steady transdermal delivery could smooth plasma concentration peaks and troughs and potentially reduce systemic exposure.

The release kinetics told a coherent mechanistic story. When the diffusion data were fitted to four classical models, the Higuchi equation emerged as the clear best fit, with a correlation coefficient of 0.9951. The Higuchi model describes drug release governed by Fickian diffusion through a matrix, and its dominance here indicates that diffusion, not matrix erosion or swelling, is the primary engine of release. The zero-order model also performed reasonably well at 0.9539, suggesting a nearly constant release rate over time, while the first-order model at 0.9291 and the Korsmeyer-Peppas model at 0.6398 lagged behind, the latter indicating that anomalous transport does not describe the system. Together, the kinetic analysis paints a picture of a nano-formulation that releases baricitinib through a diffusion-controlled mechanism, exactly the behavior a formulator would want in a patch-like delivery system intended for steady, around-the-clock drug supply.

What distinguishes this work from the crowded field of baricitinib analytical papers is its deliberate bridging of two worlds that rarely meet. Stability-indicating HPLC methods and quality-by-design approaches have thoroughly covered bulk drug and tablets, and LC-MS/MS methods have conquered plasma pharmacokinetics, but none of the prior literature was designed to handle polymer-laden transdermal matrices or the repeated-sampling demands of permeation studies. By validating a single, inexpensive RP-HPLC platform for both the assay of the finished nano-formulation and the quantification of release samples, Tabassum and Makula have effectively handed formulation scientists a complete analytical toolkit: one method that certifies content uniformity on day one and then tracks every microgram that crosses the membrane over the next 24 hours. As JAK inhibitors continue to migrate toward dermatological applications such as atopic dermatitis and alopecia areata, where topical and transdermal delivery could localize therapy and limit systemic side effects, methods like this one will become the quiet infrastructure that makes such products testable, regulatable, and ultimately manufacturable. The study, funded by ANRF and conducted at JNTU Hyderabad, is open access, allowing laboratories worldwide to adopt the chromatographic conditions and validation framework directly.

Subject of Research: Validated RP-HPLC quantification of baricitinib in transdermal nano-formulations and its application to in vitro Franz diffusion release studies

Article Title: Quantification of Baricitinib and Franz diffusion study in transdermal nano-formulation by optimized and validated liquid chromatographic method

Article References: Tabassum, S., & Makula, A. (2026). Quantification of Baricitinib and Franz diffusion study in transdermal nano-formulation by optimized and validated liquid chromatographic method. Discover Chemistry, 3(1), Article 512. https://doi.org/10.1007/s44371-026-00897-x

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00897-x

Keywords: baricitinib, RP-HPLC, transdermal drug delivery, nano-formulation, Franz diffusion, method validation, ICH Q2(R2), drug release kinetics, Higuchi model, JAK inhibitor, pharmaceutical analysis, quality control

The triple combination is becoming increasingly common in the management of type 2 diabetes, and for good reason. Each drug attacks high blood sugar through a different biological route: metformin suppresses glucose production in the liver and improves insulin sensitivity, gliclazide prods the pancreas to release more insulin, and dapagliflozin forces the kidneys to flush excess glucose out through the urine. Combining them in a single pill improves patient compliance and delivers better glycaemic control than any one agent alone. But that therapeutic synergy creates an analytical headache, because a quality-control laboratory must be able to verify the exact amount of each ingredient in every batch before the tablets reach patients.

The difficulty lies in chemistry. Metformin is a small, strongly polar, highly hydrophilic molecule with a log P value of roughly minus 2.64, which means it barely interacts with the oily, hydrophobic surface of a reverse-phase column and tends to zip through unretained. Dapagliflozin and gliclazide, by contrast, are far more lipophilic, with log P values around 2 or higher, so they cling to the stationary phase much longer. On top of that, the dose disparity is enormous: commercial tablets contain 500 to 1000 milligrams of metformin, 40 to 80 milligrams of gliclazide, and a mere 5 to 10 milligrams of dapagliflozin, so any single method must accurately quantify compounds whose concentrations in solution differ by orders of magnitude.

Led by Rajendra Patel, with Nishith Teraiya and Anjali Prajapati, all of the K.B. Institute of Pharmaceutical Education and Research in Gandhinagar, the team systematically tuned every variable that governs chromatographic behavior. They tested water-methanol and water-acetonitrile mixtures in various ratios, but unbuffered systems produced broad, asymmetrical peaks with poor resolution. The breakthrough came from adding a volatile 20 millimolar ammonium acetate buffer adjusted to pH 3.0 with ortho-phosphoric acid. At that acidity, metformin remains fully protonated and water-loving, so it elutes first, while the more lipophilic dapagliflozin and gliclazide linger progressively longer on the hydrophobic C18 stationary phase, producing clean, well-resolved peaks.

The final recipe is elegantly simple. Separation occurs on a Kromasil C18 column, 250 millimeters long with a 4.6 millimeter internal diameter and 5 micrometer particles, using a mobile phase of the acetate buffer and acetonitrile mixed 35:65 by volume, pumped at a constant 0.8 milliliters per minute in isocratic mode. A UV detector set at 224 nanometers, a wavelength where the absorption spectra of all three drugs overlap acceptably, monitors the eluate. Under these conditions metformin appears at 2.47 minutes, dapagliflozin at 3.90 minutes, and gliclazide at 6.46 minutes. Because the solvent composition never changes during the run, the method avoids the complexity, variability, and extra solvent consumption of gradient elution, keeping both analysis time and operating costs low.

Validation followed the International Council for Harmonisation’s Q2 (R2) guidelines, the global benchmark for analytical procedures. Calibration curves were linear across 125 to 375 micrograms per milliliter for metformin, 2.5 to 7.5 for dapagliflozin, and 15 to 45 for gliclazide, with correlation coefficients all above 0.997. Recovery experiments, in which known amounts of standard drug were spiked into tablet samples at 80, 100, and 120 percent of target, yielded recoveries between 98 and 102 percent for every analyte, demonstrating negligible interference from tablet excipients. Precision testing, repeated within a single day and across three separate days, produced relative standard deviations consistently below 2 percent, the accepted threshold for repeatability in pharmaceutical analysis.

The robustness trials are particularly reassuring for routine laboratories. The researchers deliberately nudged the method’s settings, slightly altering mobile phase composition, flow rate, detection wavelength, buffer pH, and column temperature, and found that the separation held up every time, with peaks remaining symmetrical, well resolved, and statistically unchanged. Sample solutions stored for 48 hours at room temperature and at refrigerator temperature showed no degradation and no loss of assay value, meaning laboratories can prepare samples in advance without compromising results. Limits of detection and quantification, calculated from the regression statistics of the calibration lines, confirmed the method is sensitive enough for the low-dose dapagliflozin component.

The most dramatic evidence for the method’s stability-indicating power came from forced degradation studies, which regulators require to prove that an analytical method can spot decomposition before it spots nothing at all. The team exposed the drugs to 0.1 normal hydrochloric acid for one hour, 0.1 normal sodium hydroxide for two hours, 3 percent hydrogen peroxide for one hour, 40 degrees Celsius heat for one hour, and direct sunlight for two hours. Each stressor told a chemical story: gliclazide degraded most under acid, consistent with hydrolysis of its sulfonylurea linkage; dapagliflozin proved most vulnerable to light, its aromatic glucoside structure susceptible to photo-oxidation; and metformin, shielded by its highly polar biguanide scaffold, stayed comparatively stable even under heat. Crucially, in every case the degradation products eluted as separate peaks that never overlapped the three drug peaks.

Applied to a real commercial tablet containing 10 milligrams of dapagliflozin, 60 milligrams of gliclazide, and 500 milligrams of metformin, the method returned assay values of 101.52, 98.19, and 99.64 percent respectively, comfortably within pharmacopoeial expectations and confirming that the technique works outside the pristine world of pure standards. That real-world performance matters because regulators and manufacturers increasingly rely on such methods for batch release, shelf-life determination, and post-market surveillance. A method that is simultaneously accurate, robust, and stability-indicating gives quality-control chemists a single, streamlined workflow where they previously might have needed multiple runs or separate methods for each drug pair.

The broader significance extends past one formulation. As fixed-dose combinations multiply across modern pharmacotherapy, the analytical community faces growing pressure to verify ever more complex mixtures with fewer resources. This study demonstrates that careful exploitation of fundamental properties, lipophilicity, ionization state, and spectral overlap, can tame even a three-drug combination spanning a hundredfold dose range in a simple isocratic run. For the millions of patients taking triple antidiabetic therapy, the work represents an invisible but vital layer of assurance: every tablet’s contents can now be confirmed, and its chemical deterioration detected, in under seven minutes of chromatography.

Subject of Research: Development and validation of a stability-indicating RP-HPLC method for simultaneous quantification of dapagliflozin, gliclazide, and metformin in antidiabetic combination tablets

Article Title: Development of a robust stability-indicating RP-HPLC method for simultaneous estimation of triple antidiabetic combination containing dapagliflozin, gliclazide and metformin

Article References: Patel, R., Teraiya, N., & Prajapati, A. (2026). Development of a robust stability-indicating RP-HPLC method for simultaneous estimation of triple antidiabetic combination containing dapagliflozin, gliclazide and metformin. Discover Chemistry, 3(1), Article 518. https://doi.org/10.1007/s44371-026-00978-x

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00978-x

Keywords: RP-HPLC, dapagliflozin, gliclazide, metformin, type 2 diabetes, stability-indicating method, forced degradation, pharmaceutical analysis, ICH Q2 (R2), chromatography, quality control, fixed-dose combination

The molecule at the center of the study, 5-[(Z)-1,3-thiazol-2-yldiazenyl]quinolin-8-ol, abbreviated TDQ, belongs to the azo dye family, compounds defined by their signature nitrogen-nitrogen double bond, the azo group, which gives them their intense colors. Azo dyes have historically dominated textiles, leather, paints, and printing, but researchers have increasingly explored them in solar cells, optical systems, and even pharmacology, where azo-bearing heterocycles show antibacterial, antiviral, and antifungal activity. Quinoline, the second structural element of TDQ, brings its own electrochemical pedigree: the redox behavior of quinoline derivatives has attracted sustained research interest, making the pairing of a quinoline scaffold with a thiazole-linked azo bridge a logical candidate for electrode modification.

Synthesis of the dye followed a classic diazotization-coupling route performed under carefully controlled cold conditions. The team dissolved 2-aminothiazole in concentrated hydrochloric acid and rapidly chilled the mixture in an ice-salt bath to roughly 0 to 5 degrees Celsius before adding nitrosylsulfuric acid to generate the diazonium salt. After two hours of stirring at the same low temperature, the diazonium solution was combined with an alkaline solution of 8-hydroxyquinoline, with the pH held between 5 and 6 throughout the coupling step. Thin-layer chromatography tracked the reaction to completion, and the resulting dark red solid was filtered, washed, dried, and recrystallized from ethanol, delivering a 70 percent yield with a melting point of 95 to 96 degrees Celsius.

Structural confirmation relied on a battery of spectroscopic techniques. Infrared spectroscopy revealed the hydroxyl stretch of the quinoline group at 3382 inverse centimeters, aromatic carbon-hydrogen stretches at 2929, carbon-nitrogen and carbon-sulfur vibrations at 1602 and 778, and, critically, the azo linkage at 1454 inverse centimeters. Proton nuclear magnetic resonance in DMSO-d6 showed the expected hydroxyl singlet near 9.0 ppm alongside aromatic signals between 6.82 and 7.37 ppm. Ultraviolet-visible spectra recorded in DMSO, DMF, ethanol, and acetone displayed sharp absorptions at 414, 396, 386, and 409 nanometers respectively, with DMSO giving the strongest response, while mass spectrometry produced a molecular ion peak at m/z 257.3, consistent with the formula C12H8N4OS.

To build the sensor, the researchers ground one milligram of TDQ with graphite powder and silicon oil in a 70:30 ratio for half an hour, then packed the paste into a 3-millimeter electrode cavity. Electrochemical benchmarking against a bare carbon paste electrode used the standard potassium ferrocyanide redox probe in 1 M potassium chloride. The bare electrode showed weak redox peaks and large peak separations, hallmarks of slow electron transfer and a limited active surface. The TDQ-modified version, by contrast, delivered markedly higher peak currents at reduced overpotential, and calculations based on the Randles-Sevcik equation put the electroactive surface area at 0.04526 square centimeters, well above the 0.0267 square centimeters of the unmodified paste.

Impedance spectroscopy reinforced that story. Nyquist plots showed a semicircle at high frequencies whose diameter reflects charge transfer resistance: the bare electrode registered 234.82 ohms, while the TDQ-modified electrode dropped to 177.47 ohms, indicating faster interfacial electron transport and more efficient ion pathways. Bode plots added a capacitive dimension, with the modified electrode displaying more negative phase angles at low frequencies, a sign of stronger charge retention and better energy storage behavior. The authors note that this combination of lower resistance and enhanced capacitance makes the dye-modified surface attractive not only for sensing but potentially for energy storage applications as well.

With the platform validated, the team turned to the three target analytes in 0.2 M phosphate buffer. pH optimization across the range 5.8 to 7.4 showed peak currents rising to a maximum at pH 7.0, the physiological value, which was adopted for all subsequent experiments. Scan rate studies then probed the underlying mechanism: for dopamine, a log-log slope of 1.012 indicated an adsorption-controlled process, while uric acid’s slope of 0.370 pointed to diffusion control, and paracetamol’s slope of 0.474 likewise suggested diffusion-dominated behavior. Concentration studies from 10 to 100 micromolar produced calibration curves with correlation coefficients of 0.9979 for dopamine, 0.9982 for uric acid, and 0.98 for paracetamol.

The detection limits, calculated as three times the standard deviation divided by the calibration slope, came out at 6.86 micromolar for dopamine, 10.28 micromolar for uric acid, and 15.93 micromolar for paracetamol, with corresponding quantification limits of 21.15, 34.29, and 42.58 micromolar. The most striking result, however, came from simultaneous detection. In cyclic voltammetry, the modified electrode resolved three distinct oxidation peaks at 0.265 volts for dopamine, 0.554 volts for uric acid, and 0.875 volts for paracetamol, giving peak-to-peak separations of 0.289 and 0.321 volts. Differential pulse voltammetry sharpened the discrimination further, with separations of 0.227 and 0.362 volts, allowing all three compounds to be identified and quantified in a single run.

Practical durability and real-world performance rounded out the evaluation. Across five identically prepared electrodes, the relative standard deviation was just 0.85 percent, and the sensor retained 94 percent of its original dopamine response after twenty days of laboratory storage. When the team applied the standard addition method to a commercially available dopamine hydrochloride injection diluted into buffer, recoveries of spiked samples ranged from 97 to 102 percent, demonstrating that the sensor can deliver accurate measurements in a genuine pharmaceutical matrix rather than only in idealized solutions.

The broader significance lies in the simplicity and economy of the approach. Carbon paste electrodes are cheap, easy to prepare, and easy to refresh, and a milligram-scale dye modifier transforms their otherwise mediocre electrochemistry into a selective, stable sensing platform. Because dopamine imbalances are linked to Parkinson’s disease, Alzheimer’s disease, schizophrenia, and Huntington’s disease, uric acid levels flag kidney failure, pneumonia, and metabolic disorders, and paracetamol monitoring underpins safe use of one of the world’s most common analgesics, a single low-cost electrode that reads all three simultaneously could find a home in clinical labs, pharmaceutical quality control, and point-of-care diagnostics. The Davangere team’s work adds a quinoline-azo dye to the growing toolbox of molecular modifiers, showing that sometimes the fastest route to better biosensing runs through the chemistry of color.

Subject of Research: Electrochemical detection of dopamine, uric acid, and paracetamol using a quinoline-azo dye modified carbon paste electrode

Article Title: Electrochemical sensing of dopamine, uric acid, and paracetamol using a quinoline-azo dye modified carbon paste electrode

Article References: Paalaplara, K. H., Chinnagiri, K. T., Chinnagiri, R. T., & Thippandegowdru, R. M. (2026). Electrochemical sensing of dopamine, uric acid, and paracetamol using a quinoline-azo dye modified carbon paste electrode. Discover Electrochemistry, 3(1), Article 42. https://doi.org/10.1007/s44373-026-00127-0

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00127-0

Keywords: electrochemical sensor, azo dye, quinoline, carbon paste electrode, dopamine, uric acid, paracetamol, cyclic voltammetry, differential pulse voltammetry, electrocatalysis, detection limit, pharmaceutical analysis