The material was synthesized through a two-step hydrothermal and phosphorization strategy. Its three-dimensional nanoflower architecture consists of interconnected nanosheets, producing a hierarchical structure with a large specific surface area and abundant accessible active sites. When deposited on the glassy carbon electrode, NiCoP exhibited good electrocatalytic activity toward the oxidation of hydroquinone, catechol and acetaminophen.

The sensor’s calibrated operating ranges extended from 10 to 100,000 micromolar for hydroquinone, from 25 to 19,000 micromolar for catechol and from 25 to 15,000 micromolar for acetaminophen. The hydroquinone range spans four orders of magnitude, while the ranges for catechol and acetaminophen each span approximately three orders of magnitude. The reported detection limit for hydroquinone was the lowest of the three, followed by acetaminophen and then catechol.

These values characterize performance under the optimized conditions used by the researchers; the supplied study summary does not provide the number of replicate measurements or the uncertainty estimates associated with each calibration result. Real-water testing provided the practical validation of the sensor. The investigators quantified hydroquinone, catechol and acetaminophen in water samples and reported satisfactory recoveries for all three analytes, indicating that the electrode could measure the targets in the tested samples as well as under controlled laboratory conditions.

The available evidence does not identify the number or composition of the real-water samples, the full set of tested interferents or the extent to which results would change across other water matrices. The findings support the use of NiCoP as a promising sensing material for environmental monitoring, but they do not establish performance in every environmental setting or establish a clinical use for the sensor.

Subject of Research: Electrochemical sensing of hydroquinone, catechol and acetaminophen with a bimetallic NiCoP nanoflower electrode

Article Title: Bimetallic NiCoP nanoflowers as an efficient electrochemical platform for simultaneous detection of hydroquinone, catechol, and acetaminophen

Article References: Chang, T., Shi, Y., Wu, P., Xie, W., Hao, R., Gao, X., & Lu, W. (2026). Bimetallic NiCoP nanoflowers as an efficient electrochemical platform for simultaneous detection of hydroquinone, catechol, and acetaminophen. Journal of Materials Science, 61(42), 33005-33018. https://doi.org/10.1007/s10853-026-13707-7

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13707-7

Keywords: NiCoP, electrochemical sensor, nanoflowers, glassy carbon electrode, hydroquinone, catechol, acetaminophen, environmental monitoring, bimetallic phosphide, water analysis, Bimetallic, efficient

The driving problem is the relentless spread of emerging contaminants. Industrialization, agricultural intensification, and rising pharmaceutical consumption have dispersed antibiotics such as sulfamethoxazole and ciprofloxacin, proton pump inhibitors like esomeprazole, and organophosphorus pesticides into water bodies, soils, food, and biological fluids at concentrations from nanograms to micrograms per liter. These compounds raise concerns ranging from antibiotic resistance to endocrine disruption and genotoxicity. Conventional techniques such as high-performance liquid chromatography and gas chromatography-mass spectrometry deliver excellent accuracy, but they demand expensive instrumentation, trained personnel, laborious sample preparation, and substantial organic solvent consumption, and they are poorly suited to on-site analysis.

Electrochemical sensors address many of these constraints by converting chemical information into electrical signals through oxidation or reduction reactions at the electrode-electrolyte interface. A typical three-electrode cell comprises a working electrode where the target redox reaction occurs, a reference electrode such as Ag/AgCl maintaining a stable potential, and a platinum counter electrode completing the circuit. In voltammetric techniques, the peak current follows the Randles-Sevcik relationship, scaling with the number of electrons transferred, electrode area, analyte concentration, diffusion coefficient, and scan rate. Cyclic voltammetry serves mainly as a qualitative diagnostic for reversibility and electron-transfer kinetics, while differential pulse and square wave voltammetry suppress capacitive background current and deliver the nanomolar detection limits that make trace analysis practical. Electrochemical impedance spectroscopy characterizes the interface itself, revealing charge-transfer resistance and surface-area changes upon modification.

The review identifies glassy carbon electrodes as the substrate of choice because of their wide potential window from about minus 1.0 to plus 1.5 volts versus Ag/AgCl, low background current, chemical inertness, and affordability. Bare electrodes, however, suffer from a small electroactive surface area of roughly 0.07 to 0.12 square centimeters, sluggish electron transfer, fouling, and poor selectivity. Modification strategies therefore center on two material families. Transition-metal complexes of manganese, copper, cobalt, and ruthenium offer well-defined redox centers and efficient electron mediation, while conducting polymers such as polypyrrole, polyaniline, polythiophene, poly(cytosine), and polythiourea combine high conductivity, chemical stability, film-forming ability, and dense functional groups for analyte interaction.

The standout results come from copper-phenanthroline chemistry. A poly([Cu(H2O)2P2]I2)-modified glassy carbon electrode detected the antibiotic trimethoprim down to 3.91 nanomolar over a linear range of 0.5 to 160 micromolar, with a relative standard deviation of 1.67 percent and spike recoveries of 97.50 to 103.75 percent in blood serum, urine, and cow’s milk. The same modifier detected esomeprazole at 28.90 nanomolar with 0.59 percent RSD, quantifying the drug in four commercial tablet brands at 96.05 to 107.90 percent of labeled content. A tetranuclear copper complex bridged by 4,4′-bipyridine achieved simultaneous detection of sulfamethoxazole and trimethoprim, with detection limits of 27.94 and 21.56 nanomolar respectively, RSD values as low as 0.11 percent, and more than 97 percent signal retention after 15 days.

A manganese(II) resorcinolato complex extended the approach to the DNA bases adenine and guanine, detecting both simultaneously with limits of 66.54 and 9.1 nanomolar and validating the method in urine, serum, and DNA extracts with recoveries of 96 to 104 percent. On the polymer side, a poly(cytosine)-modified electrode boosted the guanine oxidation signal 7.5-fold relative to bare glassy carbon, reaching 6.10 nanomolar with less than 1 percent RSD, and directly quantified endogenous guanine at 1.40 micromolar in DNA extracts without interference from other bases. Impedance measurements explain these gains: modification cut charge-transfer resistance from 5140 ohms to roughly 440 to 500 ohms, corresponding to about a hundred-fold enhancement in the heterogeneous electron-transfer rate constant, and tripled the electroactive area.

Mechanistic analysis underpins the performance claims. Scan-rate studies consistently showed diffusion-controlled oxidation, with log current versus log scan-rate slopes of 0.45 to 0.62 near the theoretical value of 0.5 for pure diffusion. Tafel analysis and pH-dependence data revealed one-electron, one-proton rate-determining steps for trimethoprim, esomeprazole, sulfamethoxazole, and adenine, while guanine oxidizes through a two-electron pathway, with near-Nernstian slopes of 56 to 66 millivolts per pH unit confirming coupled proton-electron transfer. The copper systems outperform the manganese platform because the Cu(II)/Cu(I) couple is more accessible and reversible, and the pi-acidic phenanthroline ligand field delocalizes charge more effectively than the resorcinolate environment.

The review is candid about limitations. Stability data stop at 14 to 21 days, far short of commercial shelf-life requirements. Only one study reported sensor-to-sensor reproducibility, and without stating the number of electrodes tested. None of the sensors was actually validated in environmental water samples; nanomolar limits measured in buffer or serum do not guarantee performance in wastewater, where natural organic matter and variable ionic strength alter fouling and selectivity. Electrode fouling under continuous protein exposure remains untested, simultaneous detection is capped at two analytes, and the claimed equivalence to USP HPLC methods lacks formal statistical comparison. Multistep synthesis of the copper complexes also adds a scale-up burden absent from the single-monomer poly(cytosine) system.

Looking forward, the review charts several converging trends. Graphene and reduced graphene oxide offer surface areas up to 2630 square meters per gram; carbon nanotubes, gold and platinum nanoparticles, metal-organic frameworks, and MXenes promise further signal amplification and preconcentration. Screen-printed electrodes and smartphone-connected handheld potentiostats point toward decentralized field testing, while wearable and microfluidic platforms could enable continuous biomarker monitoring. Artificial intelligence adds another layer: partial least squares regression and convolutional neural networks could resolve overlapping voltammetric peaks and automate interpretation, though the author cautions that large, standardized electrochemical datasets essentially do not exist, making overfitting a central risk that demands leave-one-electrode-out validation and external test sets.

The bottom line is a field at an inflection point. Modified glassy carbon electrodes now routinely deliver nanomolar detection, sub-2.5 percent precision, and validated performance across serum, urine, milk, DNA extracts, and tablets, with recoveries consistently between 95 and 106 percent. Converting these laboratory successes into deployed technology will require matrix-matched validation in real environmental waters, standardized reproducibility protocols with stated sample sizes, formal statistical benchmarking against pharmacopeial methods, open voltammetric datasets for machine learning, and scalable, low-complexity modifier synthesis. If those gaps close, the review concludes, the convergence of materials science, electrochemistry, and data science could yield sensing systems that bring laboratory-grade contaminant surveillance out of the lab and into the field.

Subject of Research: Modified electrochemical sensors for pharmaceutical and environmental pollutant detection

Article Title: A comprehensive review on modified electrochemical sensors for pharmaceutical and environmental pollutant detection: Recent advances and future perspectives

Article References: Metto, M. (2026). A comprehensive review on modified electrochemical sensors for pharmaceutical and environmental pollutant detection: Recent advances and future perspectives. Results in Chemistry, 31, Article 103966. https://doi.org/10.1016/j.rechem.2026.103966

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103966

Keywords: electrochemical sensors, glassy carbon electrode, metal-organic complexes, conducting polymers, pharmaceutical detection, environmental pollutants, sulfamethoxazole, trimethoprim, square wave voltammetry, nanomolar detection limits, electropolymerization, sensor validation

Ticagrelor is a mainstay of modern cardiology. It works by reversibly blocking the platelet P2Y12 receptor, which prevents adenosine diphosphate from activating platelets and triggering the clotting cascade. Physicians prescribe it, often alongside aspirin, to patients with acute coronary syndrome or ST-segment elevation myocardial infarction to ward off further thrombotic events. Because the drug’s therapeutic effect depends on careful dosing and because patients differ widely in how they metabolize it, analytical methods that can measure ticagrelor quickly and accurately are clinically valuable. Until now, that job has mostly fallen to chromatography-based techniques such as high-performance liquid chromatography, liquid chromatography coupled with mass spectrometry, reverse-phase HPLC, and various spectrophotometric and bio-analytical approaches. These methods are accurate but typically require expensive instrumentation, trained operators, lengthy sample preparation, and centralized laboratory facilities.

Electrochemical sensing offers an appealing alternative. By translating molecular interactions at an electrode surface into an electrical current, such sensors can be fast, cheap, portable, and sensitive. The catch is that a bare electrode rarely provides enough signal for trace-level detection of a drug in a complex biological matrix. The standard remedy is to coat the electrode with a nanomaterial or nanocomposite that boosts conductivity, surface area, and catalytic activity. The Iranian-led team behind the new study chose an unusual pairing: carbon black, an abundant and highly conductive industrial carbon, and a silver-based metal-organic framework, a crystalline coordination network built from silver ions and the organic linker 1,3,5-benzenetricarboxylic acid.

Each component brings distinct strengths. Carbon black offers excellent porosity, high surface area, strong electrical conductivity, and a wide potential window, making it an ideal conductive backbone. Metal-organic frameworks, meanwhile, are prized for their enormous surface areas, tunable structures, and high porosity, all of which improve the interface between electrode and electrolyte. In this system, the silver framework performs three critical jobs: it supplies metal-based catalytic activity, it acts as an intrinsic electrochemical signal source through its own silver-related redox chemistry, and its tunable porosity facilitates molecular diffusion while enlarging the effective surface area available for recognition events. The researchers synthesized the framework by dissolving the organic linker and silver nitrate separately in methanol, combining the solutions, and heating the mixture at 120 degrees Celsius overnight, a straightforward and economical preparation.

Microscopy and spectroscopy confirmed that the marriage worked. Field-emission scanning electron microscopy showed carbon black forming a spherical film-like coating, while the silver framework appeared as sheet-like crystals with sharp, regular morphologies. In the composite, the two components merged into a porous, spongy, interconnected architecture with no phase separation, exactly the kind of structure that maximizes both conductivity and accessible surface area. Energy-dispersive X-ray analysis and elemental mapping verified that carbon, oxygen, nitrogen, and silver were uniformly distributed throughout the material. Fourier-transform infrared spectroscopy revealed characteristic bands from the aromatic linker and carboxylate groups, and X-ray diffraction showed that the framework’s crystalline structure survived composite formation intact, with no detectable separate crystalline silver oxide or metallic silver impurity phases.

Electrochemical tests then revealed why the composite outperforms its ingredients. Using cyclic voltammetry and electrochemical impedance spectroscopy with a ferricyanide redox probe, the team found that adding carbon black to a glassy carbon electrode increased current and lowered charge-transfer resistance from 687 ohms for the bare electrode to 344 ohms. The silver framework alone, hampered by its intrinsically low conductivity, actually raised resistance to 2016 ohms. But the combined composite slashed resistance to just 221 ohms, clear evidence of synergy. Calculations based on the Randles-Sevcik equation showed the composite electrode’s electrochemically active surface area reached 0.045 square centimeters, more than double the 0.021 square centimeters of the bare electrode.

Perhaps the most intriguing finding concerns how the sensor actually detects ticagrelor. Neither the bare electrode nor the carbon-black-modified electrode produced a distinct response to the drug. Instead, the signal originates from the silver-containing framework itself: the drug, with its sulfur-, nitrogen-, and oxygen-containing functional groups, accumulates on the electrode through affinity interactions with accessible silver sites and hydrogen bonding with the organic linker, thereby blocking the electroactive silver sites and suppressing the silver-related current. The result is an indirect, signal-off mechanism in which the drug’s presence is measured by how much it dampens the baseline signal. Carbon black amplifies this effect dramatically. The drug-induced current change was approximately 519 microamperes at the composite electrode versus 196 microamperes at the framework alone, a roughly 2.6-fold enhancement, because the conductive carbon network improves electron transfer between the electroactive silver sites and the underlying electrode while also dispersing the framework particles more effectively.

After optimizing the composite ratio, buffer pH, and salt concentration, the sensor delivered striking analytical performance. Differential pulse voltammetry yielded a linear response across an extraordinarily wide concentration range spanning 0.01 to 2500 nanomolar, with a correlation coefficient of 0.9983 and a calculated detection limit of 0.0033 nanomolar. For comparison, previously reported ticagrelor sensors based on carbon paste electrodes modified with multiwalled carbon nanotubes and titanium nanoparticles, zeolite-modified carbon paste, or solid gold electrodes achieved detection limits in the hundreds of nanomolar to micromolar range. The authors caution that such cross-study comparisons should be interpreted carefully, since electrode architectures, sample preparation, and detection-limit calculations differ, but the numbers nonetheless underline the platform’s analytical promise. Microscopy before and after testing also confirmed the composite’s structural stability under operating conditions.

The sensor proved robust in the ways that matter for real-world use. It tolerated high concentrations of structurally related drugs and common biological interferents, including ticlopidine, clopidogrel, warfarin, ascorbic acid, dopamine, uric acid, and glucose. Five identical electrodes produced responses with a relative standard deviation of just 2.5 percent, and five repeated measurements on a single electrode gave 3.1 percent. After fifteen days of storage at room temperature, the electrode retained 93 percent of its initial response, and fifty consecutive voltammetric cycles preserved 95.32 percent of the original signal. Most importantly, when the team spiked human serum samples with 50, 100, and 200 nanomolar ticagrelor after protein precipitation, the sensor recovered between 99.5 and 101.2 percent of the added drug with relative standard deviations below 2.8 percent, demonstrating that the platform can function in a genuine biological matrix rather than only in pristine buffer solutions.

The broader significance of the work lies in its demonstration that cheap, readily available materials can be engineered into sensors rivaling far costlier analytical instruments. Carbon black costs pennies, the silver framework is synthesized in a single overnight reaction, and the entire electrode modification involves ultrasonicating the two powders in a drop of solvent and drying five microliters onto a glassy carbon electrode. A sensor built this way could, in principle, support point-of-care or bedside monitoring of ticagrelor, helping clinicians tailor antiplatelet therapy to individual patients and detect abnormal drug levels before they translate into bleeding or clotting complications. The signal-off design, in which the analyte suppresses a built-in silver redox signal, also offers a template that other researchers could adapt to different drug molecules capable of binding silver sites. While further validation in larger clinical studies would be needed before any diagnostic deployment, the study adds a compelling entry to the growing toolkit of metal-organic framework sensors and shows how the right nanoscale partnership can turn an ordinary electrode into an extraordinarily perceptive one.

Subject of Research: Electrochemical detection of the antithrombotic drug ticagrelor using a silver metal-organic framework and carbon black nanocomposite-modified electrode

Article Title: Electrochemical sensor based on Ag-metal organic framework/carbon black nanocomposite for the selective detection of Ticagrelor

Article References: Roushani, M., Karazan, Z. M., & Makki, I. S. (2026). Electrochemical sensor based on Ag-metal organic framework/carbon black nanocomposite for the selective detection of Ticagrelor. Results in Chemistry, 31, Article 103939. https://doi.org/10.1016/j.rechem.2026.103939

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103939

Keywords: ticagrelor, electrochemical sensor, metal-organic framework, carbon black, nanocomposite, glassy carbon electrode, antithrombotic drug, differential pulse voltammetry, human serum, detection limit, silver framework, P2Y12 receptor

The stakes behind this kind of analytical chemistry are higher than they might first appear. Chloramphenicol is a broad-spectrum antibiotic that once saw wide clinical use, including historic applications against pneumonic plague and typhoid, but it has been banned or tightly restricted in food-producing animals in many jurisdictions because residues in meat, milk, honey, and aquaculture products can pose direct toxic risks to consumers. Beyond acute toxicity, the presence of antibiotic residues in the food supply is one of the pressures that drives the emergence and spread of antimicrobial resistance, a public health threat that regulators worldwide now treat with mounting urgency. European regulations, including Commission Regulation (EU) 2019/1871 with its reference point for action and the monitoring framework of Regulation (EU) 2021/808, impose strict performance demands on any method used to police banned veterinary drug residues, which is precisely why faster, cheaper, and more portable detection platforms attract so much research attention.

Conventional methods for detecting chloramphenicol are powerful but cumbersome. Liquid chromatography coupled to mass spectrometry remains the gold standard for confirmatory analysis, and it has been applied to everything from honey to chicken muscle and eggs, often after dispersive solid-phase extraction or other cleanup steps. Capillary electrophoresis and high-performance liquid chromatography with ultraviolet detection have also been used, while immunoassays such as enzyme-linked immunosorbent assays offer screening capability at lower cost, and commercial ELISA kits have recently been comparatively assessed for meat and aquaculture products under the new European rules. Fiber optic chemiluminescent immunosensors and time-resolved fluorescence methods have pushed toward on-site use. Each of these techniques, however, typically involves sample preparation, instrumentation, trained operators, and turnaround times that are poorly matched to the pace of modern food distribution. Electrochemical sensors promise something different: direct electrical readout, small footprints, low reagent consumption, and the potential for field deployment.

The core of the new sensor is a zirconium metal-organic framework, a class of crystalline materials in which zirconium clusters are linked by organic struts into porous, cage-like architectures. Zr-MOFs have become favorites in the sensing literature because they combine high surface area with remarkable chemical and thermal stability, and they have already been engineered into platforms for detecting nitrofurazone, amoxicillin, tetracyclines, sulfonamides, and chlorpromazine, among other analytes. Recent reviews have highlighted zirconium-based frameworks as especially promising for food safety sensing. In the new work, the framework provides an abundance of adsorption and catalytic sites, while its ordered porosity concentrates chloramphenicol molecules near the electrode surface, amplifying the current signal that the electrochemical measurement records.

The second ingredient is the most surprising: gadoteridol, a gadolinium-based contrast agent that radiologists inject into patients to sharpen magnetic resonance images. Gadolinium complexes are prized in MRI because the gadolinium ion shortens the relaxation time of nearby water protons, brightening the image, and gadoteridol is one of the clinically approved macrocyclic agents with a well-characterized safety profile for that purpose. Its appearance in an electrochemical sensor reflects a growing recognition that gadolinium chemistry can do more than light up scans. Several recent studies have exploited gadolinium compounds for chloramphenicol detection, including gadolinium tungstate paired with sulfur-doped carbon nitride, nanostructured gadolinium tungstate on reduced graphene oxide, and iron-doped gadolinium oxide nanoparticles, all of which reported enhanced electron transfer and electrocatalytic activity. In the new composite, the gadoteridol component is proposed to contribute gadolinium-centered redox activity and electronic mediation that accelerates the reduction of chloramphenicol’s nitro group, the electrochemical fingerprint the sensor reads out.

The third component, carbon fiber, supplies the conductive backbone. Carbon-based nanomaterials have long served as electrode modifiers because they conduct electricity efficiently, resist corrosion, and present large accessible surfaces. Carbon fibers have previously been functionalized with polydopamine for chloramphenicol sensing, and carbon nanofibers decorated with zirconium dioxide have delivered strong analytical performance in earlier studies. In the hybrid architecture, the fibers interweave with the MOF crystals to form a percolating network that shuttles electrons from the catalytic sites to the underlying glassy carbon electrode, while the ultrasonication-assisted synthesis ensures the three phases are intimately mixed rather than simply layered on top of one another.

Characterization and electrochemical testing together tell the story of why the composite works. Scanning electron microscopy revealed the morphology of the hybrid material, X-ray diffraction confirmed its crystalline structure, and energy-dispersive X-ray analysis verified the elemental composition expected from the three components. The team then interrogated the electrode with the standard toolkit of electroanalysis: electrochemical impedance spectroscopy to measure how readily charge crosses the electrode-solution interface, cyclic voltammetry to map the redox behavior of chloramphenicol at the surface, and differential pulse voltammetry to achieve the fine discrimination needed for quantitative work at low concentrations. These techniques were used to systematically optimize the operating parameters, tuning the conditions under which the reduction signal for chloramphenicol is largest and cleanest.

The analytical figures of merit place the sensor among the competitive entries in a crowded field. A detection limit of 0.2 micromolar and a sensitivity of 1.5 microamperes per micromolar per square centimeter compare favorably with other recent chloramphenicol platforms, from tin oxide on reduced graphene oxide and tin-reduced graphene oxide screen-printed electrodes to nickel-cobalt MOF composites, molybdenum disulfide on carbon nanomaterials, cobalt oxide on graphene, and copper-molybdenum sulfide nanocomposites. Equally important for any sensor hoping to leave the laboratory, the electrode demonstrated strong selectivity against potential interferents, reproducibility from electrode to electrode, and operational stability over repeated measurements. The recovery experiments in food samples, with relative standard deviations under five percent, address the question that matters most to regulators: whether the sensor can find the antibiotic in the messy chemical company of a real food matrix rather than in a pristine buffer solution.

The study is not the team’s first foray into this territory. The same group has previously reported a graphene oxide, copper oxide, and zinc oxide nanocomposite combined with carbon fibers for chloramphenicol detection, and a molybdenum disulfide and carbon nanotube aerogel-based PEDOT nanocomposite for simultaneously detecting chloramphenicol and furazolidone in food. A related hybrid Zr-MOF, carbon nanotube, and nanocellulose sensor achieved dual detection of furazolidone and chloramphenicol. The new work extends that program by introducing a clinically validated MRI contrast agent into the electrode material itself, a design choice that highlights how researchers are increasingly raiding unexpected corners of chemistry, from diagnostic medicine to coordination polymers, in search of better electrocatalysts.

What comes next will determine whether the sensor remains an elegant laboratory demonstration or becomes a practical screening tool. The published work establishes the composite’s synthesis, characterization, and analytical performance, and the encouraging recovery rates in food samples point toward real-world applicability, but translating a modified glassy carbon electrode into a deployable device typically requires integration with portable potentiostats, disposable electrode formats such as screen-printed substrates, and validation across many more food types and laboratories. The broader context is favorable: regulators continue to tighten surveillance of banned veterinary residues, proficiency tests such as the Italian national reference laboratory’s exercise on chloramphenicol in honey underscore how demanding routine control can be, and the literature on Zr-MOF sensing platforms for food safety is expanding rapidly. If hybrid electrodes like this one can be manufactured reliably and cheaply, the unlikely marriage of an imaging drug, a porous zirconium framework, and carbon fiber may help put rapid antibiotic residue testing within reach of far more of the food supply chain than today’s chromatography suites can cover.

Subject of Research: Electrochemical detection of chloramphenicol antibiotic residues in food using a hybrid Zr-MOF/gadoteridol/carbon fiber composite electrode

Article Title: A Hybrid Zr-MOF/gadoteridol/carbon fiber composite glassy carbon electrode for rapid and sensitive electrochemical determination of chloramphenicol in food samples

Article References: R. B., R., Reddy, S., K.N., H., & Achary, G. (2026). A Hybrid Zr-MOF/gadoteridol/carbon fiber composite glassy carbon electrode for rapid and sensitive electrochemical determination of chloramphenicol in food samples. Ionics. https://doi.org/10.1007/s11581-026-07548-2

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07548-2

Keywords: chloramphenicol, Zr-MOF, gadoteridol, carbon fiber, electrochemical sensor, food safety, antibiotic residues, metal-organic frameworks, voltammetry, antimicrobial resistance, glassy carbon electrode, gadolinium

Quercetin is a naturally occurring flavonoid found in fruits, vegetables, and grains, and it has attracted enormous attention for its antioxidant, anti-inflammatory, antibacterial, and cardiovascular protective effects. Those properties have made it a staple ingredient in pharmaceuticals and nutritional supplements around the world. But the same popularity has created a hidden environmental problem. Excessive intake or uncontrolled release of quercetin can induce adverse effects such as nephrotoxicity, and its polyhydroxyl structure allows it to bind strongly with metal ions, which can further increase its potential toxicity in environmental systems. Tracking this molecule in rivers, estuaries, and coastal waters has therefore become a genuine analytical priority.

Existing methods for measuring quercetin include high-performance liquid chromatography, UV-visible spectrophotometry, capillary electrophoresis, and electrochemical techniques. Electrochemical sensing stands out because it offers high sensitivity, fast response, low cost, and simple operation. Yet the literature is crowded with sensors that come with strings attached. Some achieve impressively low detection limits using complex nanocomposites, but their synthesis involves multiple procedures that hinder reproducibility and large-scale application. Polymer-modified electrodes often show narrow practical linear ranges, molecularly imprinted polymer sensors require template removal and multi-component assembly, and advanced bimetallic or ionic liquid platforms depend on specialized materials. The field has been waiting for a design that combines simple fabrication with reliable performance in messy real-world samples.

The new sensor tackles this challenge with a two-part strategy. The first component is MOF-79, a metal-organic framework constructed from titanium nodes and adenine ligands. Metal-organic frameworks are crystalline lattices in which metal centers are connected by organic linkers, producing structures with enormous internal surface areas, tunable pores, and well-defined architectures. Titanium-based MOFs in particular have demonstrated good chemical stability and promising electronic properties. The second component is gold, a metal prized in electrochemistry for its excellent conductivity, catalytic activity, and biocompatibility. Gold nanoparticles on their own tend to aggregate during synthesis or operation, which shrinks the active surface area and degrades sensing performance. The porous MOF-79 framework solves this by acting as a rigid scaffold that keeps the gold nanoparticles uniformly dispersed and prevents them from clumping.

The researchers synthesized the composite through a straightforward hydrothermal route. MOF-79 was first grown in a Teflon-lined autoclave from titanium dioxide, adenine, and an oxalic acid solution held at 70 degrees Celsius for 15 hours. The resulting solid was then stirred with chloroauric acid under alkaline conditions, reducing the gold precursor into metallic nanoparticles distributed across the framework. A drop of the suspended material was deposited onto a polished glassy carbon electrode, producing the finished Au@MOF-79/GCE sensor. Characterization by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy confirmed that the crystalline framework survived the gold incorporation intact and that the gold had been reduced to its metallic state, with characteristic Au 4f signals appearing at 83.1 and 87.0 electron volts.

Electrochemical testing revealed exactly why the marriage of gold and MOF works so well. In cyclic voltammetry experiments, the Au@MOF-79 electrode produced the strongest redox peaks for quercetin among three electrodes tested, outperforming both a bare glassy carbon electrode and one modified with MOF-79 alone. The porous framework showed a strong affinity for quercetin, enriching the molecule near the electrode surface, while the loaded gold enhanced the detection capability by accelerating electron transfer. When the team varied the scan rate from 10 to 175 millivolts per second, the peak currents rose in strict proportion to the sweep speed, with a correlation coefficient of 0.999 for the anodic peak. The reduced peak-to-peak separation after gold incorporation pointed to faster, more reversible charge transfer, and the overall behavior indicated an adsorption-controlled process in which the porous structure gathers more quercetin onto the electrode surface.

The team also fine-tuned the operating conditions. Peak currents remained above 2 microamps across a broad pH range from 5.7 to 8.0, but the signal reached its maximum at pH 7.0, where it was amplified roughly 1.7-fold compared with other values. Using differential pulse voltammetry at this optimum, the sensor delivered a linear response to quercetin concentrations spanning from 3.04 times ten to the minus fifth to 1.196 times ten to the minus third molar, with a detection limit of 6.0 times ten to the minus sixth molar. That limit sits at the micromolar level, higher than the best noble-metal-plus-carbon systems reported in the literature, but the authors argue the trade-off is deliberate. Their electrode was designed with an emphasis on structural stability, reproducibility, and straightforward fabrication rather than ultra-low detection limits achieved through sophisticated architectures, and the wide linear range and stable response make the sensitivity sufficient for practical determination.

Durability and selectivity proved equally convincing. A chronoamperometric run lasting 2600 seconds produced a smooth curve without obvious fluctuation, demonstrating high short-term operational stability. In interference experiments, metal ions including lead, lithium, iron, calcium, and cobalt were introduced at concentrations equal to that of quercetin, and none of them significantly disturbed the electrochemical signal. The real test, however, came from the environment itself. The researchers collected seawater from the Ten Mile Golden Beach in Jinzhou, Liaoning Province, mixed it fifty-fifty with phosphate buffer, and spiked it with known quercetin concentrations. The sensor tracked the added quercetin with a linear calibration closely mirroring the one obtained in pure buffer, and recovery measurements showed relative standard deviations between 2.1 and 3.8 percent, indicating excellent feasibility and accuracy in a matrix notorious for its salt, dissolved organic matter, and competing ions.

The significance of the work extends beyond one molecule. It offers a practical design philosophy for MOF-based electrochemical sensors destined for complex aqueous environments: let a porous framework do the enrichment work, let well-dispersed metal nanoparticles do the electron-transfer work, and keep the synthesis simple enough that the whole thing can be rebuilt reliably. As pharmaceutical consumption continues to climb worldwide, the residues of those compounds are increasingly detected in coastal and marine waters, and monitoring tools that are cheap, robust, and field-deployable will only grow in importance. A gold-studded molecular sponge that shrugs off seawater and still reads quercetin accurately is a small electrode with a large implication: environmental pharmaceutical surveillance may soon be within reach of any laboratory that can mix a few reagents and polish a glassy carbon rod.

Subject of Research: An Au nanoparticle and MOF-79 composite electrochemical sensor for detecting quercetin in seawater

Article Title: The electrochemical sensor Au@MOF-79 toward the quercetin detection in seawater

Article References: Duan, F., Yang, H., Qiao, C., Chen, J., Lin, P., & Ge, Q. (2026). The electrochemical sensor Au@MOF-79 toward the quercetin detection in seawater. Discover Electrochemistry, 3(1), Article 44. https://doi.org/10.1007/s44373-026-00117-2

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00117-2

Keywords: electrochemical sensor, quercetin, MOF-79, gold nanoparticles, metal-organic framework, seawater, differential pulse voltammetry, electrocatalysis, environmental monitoring, pharmaceutical residues, hydrothermal synthesis, glassy carbon electrode

4-Aminophenol is a small aromatic molecule with a dual identity. On one hand, it is an industrial workhorse, serving as an intermediate in the manufacture of paracetamol, dyes, and photographic developers, and it can appear as a degradation product or impurity in pharmaceutical preparations. On the other hand, it is classified as toxic and potentially carcinogenic, capable of causing severe harm to living organisms even at low concentrations. Because industrial effluents and pharmaceutical waste streams can carry the compound into rivers and groundwater, environmental agencies have long sought monitoring tools that are fast, cheap, and sensitive enough to catch dangerous levels before they spread. Traditional analytical techniques such as high-performance liquid chromatography and gas chromatography can do the job in the laboratory, but they require bulky instrumentation, trained operators, and lengthy sample preparation, none of which lends itself to routine field screening of wastewater.

Electrochemical sensing has emerged as a compelling alternative because it translates molecular recognition directly into an electrical signal. The basic idea is elegant: a working electrode, typically a glassy carbon electrode, is coated with a material that interacts selectively with the target molecule. When the analyte is oxidized or reduced at the electrode surface, the resulting current is proportional to its concentration. The challenge lies in finding coating materials that combine high conductivity or electrocatalytic activity with selectivity, so that the sensor responds to 4-aminophenol even in the presence of the many other electroactive species found in real wastewater. Over the past decade, metal-organic frameworks, or MOFs, have become one of the most popular families of such materials.

MOFs are crystalline lattices in which metal ions or clusters are connected by organic linker molecules into porous, sponge-like architectures. Their appeal for sensing is obvious: the enormous internal surface area and tunable pore sizes allow molecules to be concentrated near active sites, while the chemical identity of both metal nodes and linkers can be adjusted to tune interactions with specific analytes. In the case of MIL-53(Fe), the framework is built from iron ions and terephthalate linkers, and it possesses a famous quirk known as breathing behavior. The structure can reversibly swell and contract as guest molecules enter or leave its pores, a flexibility that has been studied extensively in adsorption science and that the authors argue contributes to the material’s analytical performance by accommodating guest molecules and facilitating their approach to the iron centers.

According to the study, this is the first reported application of pristine MIL-53(Fe) for the electrochemical detection of 4-aminophenol in contaminated water. Previous MOF-based sensors for the same target typically required complex nanocomposite preparation, combining the framework with graphene, metal nanoparticles, or other functional additives, or noble metal functionalization to achieve competitive performance. The new work demonstrates that the biocompatible iron nodes within the untouched framework are sufficient on their own. The researchers deposited the material onto a glassy carbon electrode, producing what they designate the MIL-53(Fe)/GCE, and characterized its response to 4-aminophenol using standard electrochemical techniques. The porous architecture of the framework appears to provide abundant pathways for the molecule to reach active sites, where the iron centers participate in the electron-transfer process that generates the measurable signal.

The performance figures reported by the team are impressive by any standard in the field. The modified electrode exhibited a sensitivity of 90.02 microamperes per micromolar per square centimeter, a detection limit of 40 nanomolar, and outstanding selectivity in the presence of common interferents, the co-existing compounds that ordinarily plague electrochemical measurements in complex environmental samples. To put the detection limit in context, the authors compare their sensor with previously reported systems: a Ce-MOF-based electrode achieved a detection limit of 0.08 micromolar, while Fe-MIL-101-NH2 and a MXene/Ti-MOF composite reached 0.16 micromolar. The pristine MIL-53(Fe) sensor outperforms these benchmarks while offering a simpler and more cost-effective fabrication protocol, an advantage that matters enormously when the goal is deploying sensors at scale for routine monitoring rather than producing one-off laboratory demonstrations.

Selectivity deserves particular emphasis, because it is often the Achilles heel of electrochemical detection in real matrices. Wastewater contains a cocktail of phenolic compounds, ions, surfactants, and organic matter, many of which can be oxidized at similar potentials to 4-aminophenol and thereby produce false signals. The researchers tested their electrode against common interferents and found that the sensor maintained its response to the target molecule with outstanding discrimination. This selectivity is attributed to the combination of size exclusion and specific interactions within the framework’s pores, which favor the target molecule while discouraging others from reaching the electroactive sites. The breathing behavior of the framework may also play a role, dynamically adjusting the pore environment in response to guest molecules in a way that rigid sensor materials cannot.

Perhaps the most important test for any laboratory sensor is whether it survives contact with the real world. The team applied their MIL-53(Fe)/GCE to actual wastewater samples and obtained recoveries ranging from 97.3 to 101.0 percent, a narrow window around the ideal 100 percent that indicates the sensor measures the true concentration of 4-aminophenol without significant interference or matrix effects. Recovery experiments of this kind are the gold standard for validating analytical methods, and results this close to theoretical values suggest the device could be genuinely useful for environmental monitoring programs rather than remaining a laboratory curiosity. The work was carried out at the National Centre of Excellence in Analytical Chemistry in Jamshoro, Pakistan, with support from the São Paulo Research Foundation under grants 2024/13394-1 and 2021/00356-6, reflecting an international collaboration spanning Pakistan, Saudi Arabia, and Brazil.

Beyond the immediate result, the study carries a broader message for the sensing community. The field of MOF-based electrochemistry has been racing toward ever more elaborate composites, layering frameworks onto MXenes, graphene, quantum dots, and noble metal nanoparticles in pursuit of incremental gains in sensitivity. This work suggests that sometimes the elegant answer is to step back and let the intrinsic chemistry of a well-chosen framework do the work. Iron is abundant, inexpensive, and biocompatible, and MIL-53(Fe) is among the most studied and easily synthesized MOFs in existence, with well-established scalable preparation routes. A sensor built from such a material sidesteps the cost and reproducibility problems that often accompany exotic nanocomposites, and the authors argue that its sustainable profile makes it attractive for widespread deployment.

The implications extend beyond 4-aminophenol itself. The same pristine-framework strategy could plausibly be applied to other phenolic pollutants, pharmaceutical residues, and industrial contaminants, provided the framework’s pore chemistry can be matched to the target. As concerns about micropollutants in water supplies intensify worldwide, the demand for portable, low-cost, and reliable detection technologies will only grow. A sensor that combines nanomolar sensitivity, strong selectivity, verified performance in real wastewater, and fabrication simplicity checks nearly every box on that wishlist. If the approach proves robust in further field trials, the humble iron terephthalate crystal, first synthesized decades ago and famous for its breathing pores, may find a new career as the beating heart of a new generation of environmental watchdogs, quietly converting the chemistry of polluted water into numbers that regulators and communities can act upon.

Subject of Research: Electrochemical detection of 4-aminophenol in wastewater using a pristine MIL-53(Fe) metal-organic framework modified glassy carbon electrode

Article Title: Development of MIL-53(Fe)-based electrochemical sensor for detection of 4-aminophenol in wastewater

Article References: Hyder, A., Baig, J. A., Mahar, N., Khan, Z. U., Mandelli, D., Lal, B., & Memon, A. A. (2026). Development of MIL-53(Fe)-based electrochemical sensor for detection of 4-aminophenol in wastewater. Ionics. https://doi.org/10.1007/s11581-026-07531-x

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07531-x

Keywords: 4-aminophenol, MIL-53(Fe), metal-organic framework, electrochemical sensor, wastewater, environmental monitoring, glassy carbon electrode, iron-based MOF, detection limit, water pollution, voltammetry, nanomaterials

The study, published in the journal Discover Electrochemistry, was led by Sandeep Kurundawade and Sharanappa T. Nandibewoor of KLE Technological University in Hubballi, together with colleagues at Atria Institute of Technology in Bengaluru and J.S.S. Banashankari Arts, Commerce and S.K. Gubbi Science College in Dharwad. Their choice of modifier was polyaniline, one of the oldest and best understood conducting polymers. Polyaniline is prized in materials science for its unique p-type doping chemistry, its reversible redox transitions between the leucoemeraldine, emeraldine and pernigraniline states, and its protonic conductivity, all of which allow it to alter the electronic behavior of an electrode surface. Compared with its polymeric cousins polypyrrole and polythiophene, polyaniline also offers superior environmental resilience, an essential property for a sensor intended for repeated laboratory use.

Synthesis of the polymer followed a classical route: oxidative polymerization of aniline in 1.5 molar hydrochloric acid, initiated by the gradual, drop-wise addition of ammonium persulphate while the reaction mixture was stirred. The slow addition is not decorative; it prevents over-oxidation and promotes uniform chain growth. The reaction mixture’s shift to the characteristic dark green color of polyaniline’s emeraldine salt signaled success. The researchers then characterized the product with scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Electron microscopy revealed a cohesive network of uniformly packed spherical agglomerates, while the diffraction pattern showed a broad peak near 2θ equal to 25 degrees, a signature of the polymer’s π-π stacked aromatic framework and its mildly crystalline, emeraldine-phase structure.

The heart of the sensor is a glassy carbon electrode, a workhorse of electroanalytical chemistry with a geometric area of just 0.09 square centimeters. A 1 milligram sample of polyaniline was dispersed in dimethylformamide by sonication and drop-cast onto the polished electrode, with the deposited volume optimized at 4 microliters after testing across a 2 to 8 microliter range. To measure how much the coating enlarged the electrochemically active surface, the team employed a ferricyanide redox probe and the Randles-Sevcik equation. The bare electrode’s active area was 0.04 square centimeters; with polyaniline it grew to 0.156 square centimeters, a 4.4-fold increase that translates into a far denser network of electroactive sites and correspondingly faster charge transfer.

Impedance measurements reinforced that picture. Nyquist plots, fitted to a Randles equivalent circuit, yielded charge transfer resistance values of 17.03 ohms for the bare electrode and 11.57 ohms for the modified one, while the calculated heterogeneous charge transfer rate constants rose from 1.56 × 10⁻⁵ to 2.3 × 10⁻⁵ centimeters per second and exchange currents climbed from 1.508 × 10⁻³ to 2.219 × 10⁻³ amperes. In plain terms, the polymer film does not merely add surface area; it actively lubricates the movement of electrons between the drug molecules in solution and the electrode beneath. An immersion-time study further showed that the analytical signal peaked after 40 seconds of accumulation, beyond which the response declined, likely because the available surface had saturated or an inhibitory molecular layer had formed.

With the hardware characterized, the team turned to the electrochemistry of oxybutynin itself. Cyclic voltammetry in phosphate buffer at pH 7.4, scanned between 0.5 and 1.5 volts, produced a single anodic peak with no counterpart on the reverse scan, marking the oxidation as irreversible. On the modified electrode the peak current reached 76.7 microamperes against 42.6 microamperes on bare glassy carbon, and the peak potential shifted slightly downward from 1.191 to 1.185 volts, evidence that polyaniline lowers the overpotential and eases the oxidation. Varying the pH from 3.0 to 9.2 revealed a maximum response at 7.4, close to physiological pH, and a peak potential that tracked pH with a slope of 64 millivolts per pH unit, near the Nernstian ideal of 59, indicating equal numbers of electrons and protons in the reaction.

Scan rate studies completed the mechanistic portrait. The peak current scaled linearly with the square root of the scan rate, and a log-log analysis produced a slope of 0.3285, close to the theoretical value of 0.5 for diffusion control. Applying the Laviron equation to the relationship between peak potential and scan rate gave a transfer-coefficient-electron product of 1.14, which resolved to approximately two electrons when the standard transfer coefficient of 0.5 was assumed. Combined with the pH result, the oxidation of oxybutynin at the modified electrode is therefore a diffusion-controlled, irreversible process involving two electrons and two protons, proceeding through successive electron-transfer and deprotonation steps toward an oxidized imine-type intermediate and ultimately an amine-based product.

The analytical performance is where the sensor earns its headline. Using square-wave voltammetry, a technique prized for its ability to reject background currents, the team recorded a linear response across 0.04 to 10 micromolar oxybutynin, with a detection limit of 9.16 nanomolar and a limit of quantification of 30.5 nanomolar, calculated by the standard equations based on the regression intercept’s standard deviation. That sensitivity compares favorably with previously reported oxybutynin sensors, which the authors note have tended to be either expensive, laborious to construct, or both. Selectivity testing with 100-fold excesses of citric acid, gum acacia, D-glucose, dopamine, L-ascorbic acid, sucrose, and common inorganic salts produced peak potential shifts all below the 2 percent tolerance limit, confirming the sensor’s robustness in messy real-world matrices.

The practical demonstrations may prove the most consequential part of the work. Pulverized commercial 5 milligram tablets, dissolved and diluted into the linear range, yielded recoveries in excellent agreement with the label claim, opening the door to routine pharmaceutical quality control. Human urine diluted 100-fold and spiked with known drug concentrations, along with tap water, Krishna River water from Belagavi in Karnataka, and RO-purified water, were all analyzed with acceptable recoveries, extending the sensor’s reach into pharmacokinetic monitoring and environmental surveillance of pharmaceutical contamination. Stability testing showed consistent within-day signals and retention of a high percentage of the initial response after 15 days of storage in a sealed container. Taken together, the results suggest that a coating of a cheap, easily synthesized conducting polymer can transform a routine glassy carbon electrode into a precision instrument, one well suited to clinical laboratories, quality control departments, and environmental monitoring programs that have historically been priced out of high-sensitivity drug analysis.

Subject of Research: Ultrasensitive electrochemical detection of the drug oxybutynin hydrochloride using a polyaniline-modified glassy carbon electrode sensor

Article Title: Ultrasensitive electrochemical detection of oxybutynin hydrochloride using polyaniline modified sensor

Article References: Kurundawade, S., Megalamani, M. B., Naik, K., Yaraguppi, D. A., & Nandibewoor, S. T. (2026). Ultrasensitive electrochemical detection of oxybutynin hydrochloride using polyaniline modified sensor. Discover Electrochemistry, 3(1), Article 73. https://doi.org/10.1007/s44373-026-00161-y

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00161-y

Keywords: oxybutynin hydrochloride, polyaniline, electrochemical sensor, glassy carbon electrode, square-wave voltammetry, cyclic voltammetry, overactive bladder, pharmaceutical analysis, detection limit, conducting polymer, electrocatalysis, pharmacokinetics