Square Wave Voltammetry Techniques Research Articles

Electrochemical Sensing of Phenylbutazone using Multi-Walled Carbon Nanotube Paste Electrode in Pharmaceutical and Biological Fluids

The electrochemical performance of phenylbutazone (PBZ) was studied using a multi-walled carbon-nanotube-modified paste electrode (MWCNT/CPE) using a variety of voltammetric tools like cyclic voltammetry (CV), linear sweep voltammetry (LSV), and square wave voltammetry (SWV). The results showed that the MWCNT/CPE exhibited remarkable electro-catalytic action towards the electrochemical oxidation of PBZ in a phosphate buffer solution of physiological pH 7 compared to a bare carbon paste electrode. The electro-kinetic parameters like heterogeneous rate constant, transfer coefficient, scan rate, pH, and involvement of electrons in electro-oxidation of PBZ was investigated. For bare CPE, the peak current was noted to be 19.53 μA with peak potential of 0.6871 V. For MWCNT/CPE, the peak current was 30.53 μA with peak potential of 0.6792 V. The anodic peak was analyzed, and the process was diffusion controlled. For the estimation of PBZ, a SWV technique was developed with great precision and accuracy, with a detection limit of 5.2 nM and a limit of quantification of 17 nM, in the concentration range 1 × 10−7 to 10 × 10−6 M. The MWCNT/CPE has been used successfully for PBZ detection in injection, blood, and urine samples, with recovery rates of 98.9% to 101.5%, 96.3% to101.7% and 98.3% to 102.8%, respectively.

Development of an Electroanalytical Method for Ronidazole Determination in Environmental and Food Matrices Using Boron-Doped Diamond Electrode

A novel electroanalytical approach is presented for the determination of ronidazole in environmental and food matrices by applying a cathodically pretreated boron-doped diamond electrode and the square-wave adsorptive cathodic stripping voltammetry technique. From the studies of cyclic voltammetry to investigate the electroactivity of the ronidazole molecule, the occurrence of an irreversible cathodic process was verified, which was more efficiently detected using the cathodically pretreated boron-doped diamond electrode compared to the anodically pretreated electrode. Still on the electrochemical response of ronidazole, the effects of pH and scan rate were studied and, its apparent diffusion coefficient was determined by chronoamperometry (8.20 × 10−6 cm2 s−1). Under optimal experimental conditions, the analytical curve obtained for ronidazole was linear in two concentration ranges (12.70 to 63.40 µmol L−1 and 76.04 to 126.2 µmol L−1), with a limit of detection of 2.55 µmol L−1. For intra- and inter-day repeatabilities, relative standard deviations of only 2.7 and 3.5% were verified, which demonstrated the stable analytical response of the electrode. Recovery percentages ranging from 96 to 100% were achieved in the analysis of natural water and whole milk samples. Therefore, the proposed electroanalytical method shows satisfactory analytical performance towards ronidazole determination in varied matrice samples.

Impedance and voltammetric detection of bromate in food samples using CoPcMWCNTs nanocomposites modified glassy carbon electrode

Bromate in food and water has been linked to cancer risks for lifetime exposures, and the present techniques for its detection have significant limitations that necessitate the development of new and more efficient approaches. The study describes the synthesis and characterization of CoPcMWCNTs nanocomposites before modifying a glassy carbon electrode for bromate detection. The nanocomposite CoPcMWCNTs was prepared from cobalt nanoparticles, phthalocyanine, and functionalized MWCNTs via ultrasonication. The successful synthesis of the nanomaterials was confirmed via XRD, UV–visible spectroscopy, SEM, and TEM. The CV and EIS studies in 5 mM [Fe(CN)6]4−/[Fe(CN)6]3− prepared in 0.1 M PBS (pH 7) revealed that the GCE-CoPcMWCNTs exhibited higher current response and faster electron transfer than the other electrodes. The electrochemical reduction of bromate was achieved in a solution containing 0.1 M H2SO4 at a pH of 1 using the techniques of electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). Using the SWV technique, an LoD of 1.31 μM was obtained with a sensitivity of 497.59 μA μM−1 over a linear dynamic range (LDR) of 6–20 μM. In contrast, utilizing the EIS technique yielded a lower limit of detection (LoD) of 0.32 μM, accompanied by a sensitivity of 72.42 μM kΩ−1, over a linear dynamic range (LDR) of 1–8 μM. The developed sensor exhibited good selectivity, high stability (93.5 %), and good reproducibility (% RSD; 3.9 %). The proposed sensor successfully detected bromate in bread samples, exhibiting a reasonable recovery rate. Thus, demonstrating the practical application of the sensor to detect bromate in real samples (bread).

Simultaneous estimation of total phenolic and alkaloid contents in the tea samples by utilizing the catechin and caffeine oxidation signals through the square-wave voltammetry technique

This work outlines the simultaneous estimation of the total phenolic and alkaloid contents in the tea samples by using catechin (C) and caffeine (CAF) oxidation signals at a non-modified boron-doped diamond (BDD) electrode. Two irreversible oxidation peaks, about + 1.03 (for C) and + 1.45 V (for CAF) vs Ag/AgCl in acetate buffer solution at pH 4.7, were seen in the cyclic voltammetric profile of the binary mixtures of C and CAF. In optimal conditions and utilizing the square-wave mode, the BDD electrode allows for simultaneous quantification of C and CAF within the concentration ranges of 5.0–100.0 µg mL−1 (1.72 × 10-5 − 3.45 × 10-3 mol/L) and 1.0–50.0 µg mL−1 (5.15 × 10-6 − 2.57 × 10-4 mol/L) respectively. The corresponding detection limits are 1.22 µg mL−1 (4.21 × 10-6 mol/L) for C and 0.11 µg mL−1 (5.66 × 10-7 mol/L) for CAF. Other phenolic compounds (like tannic acid, gallic acid, epicatechin, and epigallocatechin gallate) and other alkaloids (theophylline and theobromine) present in tea samples were examined for selectivity assessment. Ultimately, the applicability of the proposed approach was demonstrated by estimating the total phenolic and alkaloid contents in the black and green tea samples, expressed as C and CAF equivalents. The results obtained were contrasted against those acquired using UV–Vis spectrometry.

Electrocatalytic reduction of hydrogen peroxide in solution in the presence of polyacrylic acid and copper ions: Application for gaseous hydrogen peroxide detection

A comprehensive voltammetric investigation into the electrocatalytic electrode mechanism for the reduction of hydrogen peroxide in an aqueous polyacrylic acid solution, in the presence of Cu2+ ions, is presented. The primary objective is to lay the groundwork for the development of a straightforward electrochemical sensor for the detection of gaseous H2O2. Various electrode reaction pathways have been observed depending on the potential applied to the glassy carbon electrode. At potentials approximately −0.400 V vs. Ag/AgCl (3 mol L−1 KCl), an electrochemical reduction of H2O2 occurs. In this context, the Cu2+/Cu+ redox couple, stabilized by polyacrylic acid, acts as a redox mediator, following the EC’ reaction scheme. Additionally, a complex Fenton-like spontaneous redox chemistry takes place between Cu2+/Cu+ and H2O2 within the bulk of the polyacrylic aqueous solution. This results in the generation of a variety of reactive oxygen species (ROS), with the superoxide anion and hydroxyl radical being the most probable intermediates. The electrochemical reduction of ROS species effectively recycles H2O2 near the electrode surface, constituting an electrocatalytic mechanism of the second order. This particular electrocatalytic process is evident as a prominent reduction current tail at potentials more negative than −0.400 V. This, in conjunction with the adsorption and stabilizing influence of polyacrylic acid, facilitates exceptional analytical sensitivity for the detection of gaseous H2O2. The sensor exhibits the capability to detect concentrations of gaseous H2O2 as low as 10−11 mol L−1, accomplished through the utilization of square-wave voltammetry and other advanced voltammetric techniques.

Graphitic carbon nitride infused with PVA-Mn:ZnS modified carbon sensor for electrochemical investigation of Metoclopramide hydrochloride

The primary focus is on determining the trace amount of Metoclopramide hydrochloride (MCH) which widely used to treat gastrointestinal disorders such as gastroparesis and acid reflux. The present study involves the development of a novel carbon paste-based sensor modified with Poly vinyl alcohol capped Manganese-doped ZnS nano particles decorated g-C3N4 nanocomposite (PVA-Mn:ZnS/g-C3N4@CPE), for the detecting and investigation of MCH. Cyclic voltammetry (CV) and square wave voltammetry (SWV) were used to measure the electrochemical performance of MCH. The limit of detection and quantification is found to be 5 nM and 16 nM respectively. Using the SWV technique in pH 7.0 phosphate buffer, the examination of urine and water spiked with MCH was monitored. When PVA-Mn:ZnS/g-C3N4 nanocomposite was used as a modifier in electrode-based sensors, results in well-resolved peaks and improved electrochemical current sensitivity. The electrode material was characterized by CV, scanning electron microscopy, atomic force microscopy, and electrochemical impedance spectroscopy. The electro-oxidation of MCH was explored using electro-kinetic characteristics such as heterogeneous rate constant, accumulation time, entropy, enthalpy, Gibbs free energy and other parameters like scan rate and pH. A suitable mechanism was proposed for the number of protons and electrons involved in the electro oxidation of MCH.

Square-wave voltammetry of human blood serum

A study on voltammetric analysis of blood serum diluted in a phosphate buffer is presented using advanced square-wave voltammetry at an edge plane pyrolytic graphite electrode. The results demonstrate that even in a complex medium like human blood serum, electrochemical characterization can be achieved through the use of advanced voltammetric techniques in conjunction with an appropriate commercially available electrode, such as the edge plane pyrolytic graphite electrode, which boosts superior electrocatalytic properties. Without undergoing any chemical treatment of the serum sample, the square-wave voltammetry technique reveals, for the first time, the electrode reactions of uric acid, bilirubin, and albumin in a single experiment, as represented by well-defined, separated, and intense voltammetric signals. All electrode processes are surface-confined, indicating that the edge plane sites of the electrode serve as an ideal platform for the competitive adsorption of electroactive species, despite the extensive chemical complexity of the serum samples. The speed and differential nature of square-wave voltammetry are crucial for obtaining an outstanding resolution of the voltammetric peaks, maintaining the quasi-reversible nature of the underlying electrode processes, while reducing the impact of follow-up chemical reactions that are coupled to the initial electron transfer for all three detected species, and minimizing fouling of the electrode surface.

Electrochemical Determination of Flavonoid Fisetin in Commercial Dietary Supplements Using a Boron‐Doped Diamond Electrode

AbstractFor the first time, a boron‐doped diamond electrode was utilized to quantitatively determine flavonoid fisetin (FST). Cyclic voltammetric studies have shown that the electrochemical oxidation of FST is irreversible and well‐separated two peaks (PA1 and PA2) in 0.1 M HNO3 solution. The effects of electrode pretreatment, solution pH, nature of the supporting electrolyte, and instrumental variables on the peak current and potentials of the FST were investigated by square‐wave voltammetry (SWV) and then optimum ones were determined. It was observed that the cathodically pre‐treated BDD (CPT‐BDD) electrode‘s performance was better than the other pre‐treatment procedures for increasing the FST oxidation signal. Under optimized conditions and using the SWV technique, the response of the first anodic peak (PA1) of the FST was proportional in a concentration range of 0.5–20.0 μg mL−1 (1.7×10−6–6.9×10−5 mol L−1) with a detection limit of 0.08 μg mL−1 (2.8×10−7 mol L−1). Also, it was successfully demonstrated that the proposed method is applicable in commercial nutritional supplement formulations.

Design of a printed electrochemical strip towards miRNA-21 detection in urine samples: optimization of the experimental procedures for real sample application

MicroRNAs (miRNAs) are clinical biomarkers for various human diseases, including cancer. They have been found in liquid biopsy samples, including various bodily fluids. They often play an important role in the early diagnosis and prognosis of cancer, and the development of simple and effective analytical methods would be of pivotal importance for the entire community. The determination of these targets may be affected by the different physicochemical parameters of the specimen of interest. In this work, an electrochemical detection platform for miRNA based on a screen-printed gold electrode was developed. In the present study, miRNA-21 was selected as a model sequence, due to its role in prostate, breast, colon, pancreatic, and liver cancers. A DNA sequence modified with methylene blue (MB) was covalently bound to the electrochemical strip and used to detect the selected target miRNA-21. After optimization of selected parameters in standard solutions, including the study of the effect of pH, the presence of interferent species, and NaCl salt concentration in the background, the application of square-wave voltammetry (SWV) technique allowed the detection of miRNA-21 down to a limit in the order of 2 nM. The developed device was then applied to several urine samples. In this case too, the device showed high selectivity in the presence of the complex matrix, satisfactory repeatability, and a limit of detection in the order of magnitude of nM, similarly as what observed in standard solutions.

Highly Selective and Sensitive Sensor Based IL and CMC-MWCNTs Nanocomposite for Rutin Determination

Rutin is a natural antioxidant flavonoid compound with anti-inflammatory, antioxidant, and antiviral effects that is used to prepare drugs with wide application in clinical treatment. Therefore, the quantitative detection of rutin has important practical significance. In this work, a novel electrochemical sensor based on glassy carbon electrodes (GCEs) modified with sodium carboxymethylcellulose (CMC), multi-walled carbon nanotubes (MWCNTs), and 1-butyl-3-methylimid (ionic liquid, IL) was developed for the super-sensitive detection of the flavonoid rutin. The properties of these modified materials were analyzed by transmission electron microscope (TEM), cyclic voltammograms (CVs), and electrochemical-impedance spectroscopy (EIS). CMC was used to disperse MWCNTs to further enhance their hydrophilicity and biocompatibility. The modified MWCNTs improved the sensitivity of rutin detection. The square-wave voltammetry (SWV) technique showed that the linear range of rutin concentration determination was 0.01 μM to 1 µM and 1 µM to 10 µM. The minimum concentration detection of rutin was 0.83 nM and 6.6 nM, respectively. The proposed sensor presented good selectivity for rutin and successfully analyzed rutin content in the pharmaceutical rutin tablets. These results are consistent with those measured by ultra-high-performance liquid chromatography (UHPLC). Therefore, this sensor has latent application value in the analysis of rutin in food and drug tablets and nutraceutical samples.

Determination of salicylic acid content in pharmaceuticals using chitosan@Fe3O4/CPE electrode detected by SWV technique.

Chitosan-coated magnetite nanoparticles (Chitosan@Fe3O4) were used to modify the carbon paste electrode (Chitosan@Fe3O4/CPE) to enhance sensitivity for salicylic acid (SA) analysis using square wave voltammetry (SWV). The performance and behaviour of the purposed electrodes were investigated using cyclic voltammetry (CV). The results showed that the mixed behaviour process was observed. Furthermore, parameters affecting SWV were also studied. It was discovered that the optimum conditions were a two-linearity range of SA determination, 1-100 and 100-400 μM. The limit of detection (LOD) and the limit of quantitation (LOQ) for SA are 0.57 μM and 0.90 μM, respectively. The proposed electrodes were successfully used to determine SA in applications employing pharmaceutical samples.

PVA Capped Mn-Doped ZnS Encapsulated Nontoxic MoS2 Nano-Sheet Probe for the Sensitive Estimation of Cardiovascular β-Blocking Agent Acebutolol in Biomedical and Environmental Samples

In the present study, a novel sensor PVA capped Mn doped ZnS incorporated MoS2 nanosheet composite modified gold electrode (PVA-Mn:ZnS/MoS2@GE) has been developed for the determination of acebutolol (ACB). Cyclic voltammetry (CV) and square wave voltammetry (SWV) were used to measure the electrochemical performance of ACB. When nanocomposite PVA-Mn:ZnS/MoS2 was used as a modifier in electrode-based sensors, results in well-resolved peaks and improved electrochemical current sensitivity compared to bare gold electrode. Using the SWV technique in pH 7.0 phosphate buffer, the examination of samples of biological, environmental and tablet spiked with ACB was monitored, the limit of detection and quantification is found to be 0.38 × 10−9 M and 1.28 × 10−9 M respectively. CV, energy dispersive X-ray, scanning electron microscopy, and impedance spectroscopy were performed to characterize the electrode material. A suitable mechanism was proposed for the number of protons and electrons involved in the redox reaction of ACB.

Square wave voltammetric detection of cholesterol with biosensor based on poly(styrene--ε-caprolactone)/MWCNTs composite.

A novel poly(styrene--ε-caprolactone)/multiwalled carbon nanotubes/cholesterol oxidase film-coated glassy carbon electrode was designed for cholesterol detection by square wave voltammetry (SWV). The biosensor responded to cholesterol with a measurement concentration range between 1 and 130μM, a relative standard deviation of only 0.095% and accuracy of 100.42% ±2.85 with the SWV technique in the potential range from -0.6 to +0.6V. The limit of detection was calculated to be 0.63μM. The biosensor was preserved 91 and 84% of its initial response at the end of the 9st and 25st days, respectively. Human serum from human male AB plasma was analyzed without pretreatment except for dilution to investigate the performance of the biosensor in a complex medium.

Electrochemical stripping voltammetrical sensor based on polypyrrole exfoliated polyetheramine-montmorillonite nanocomposite for nanomolar detection of nifuroxazide.

A series of polypyrrole/polyetheramine-montmorillonite nanocomposites have been fabricated by the intercalation of different types of polyoxyalkylene amine hydrochloride (Jeffamines: D400, D2000, T5000, and T403) into montmorillonite layers via the cation-exchange process followed by in situ polymerization of pyrrole. The physicochemical characteristics of as-prepared nanocomposites were investigated using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and electrochemical impedance spectroscopy (EIS) instruments. The change of the types of Jeffamine causes a change in the geometrical structure, and surface area of nanocomposites. Noteworthy, the resulting polypyrrole/D2000-montmorillonite ([PDM-50]) nanocomposite exhibited a cauliflower-like shape with a specific surface area (116.2 m2 g-1) with the highest conductivity. Furthermore, the modified stripping voltammetric carbon paste sensor was fabricated based on 1.0% [PDM-50] nanocomposites to detect the drug nifuroxazide (NF). The sensor achieved detection limits (LD) of 0.24, and 0.9 nM of NF in the medication, and human urine fluid, respectively. This sensor showed appropriate repeatability, reproducibility, stability, and selectivity for NF sensing in different fluids accompanied by other interferents.

Square wave voltammetry as a powerful tool for studying multi-electron molecular catalysts

• SWV of homogeneous two-electron molecular catalysis is theoretically investigated. • The rigorous theory applies to wide mechanistic diversity and SWV parameters. • SWV signal can enable the determination of catalytic pathways and rate constants. • SWV components are remarkably valuable to elucidate the catalyst active form. • Accurate guidelines and data analysis protocols are given. A comprehensive theoretical investigation of the square wave voltammetry (SWV) of the homogeneous two-electron molecular catalysis of electrochemical reactions is carried out. The SWV signal is studied as a function of the pulse time, the SW amplitude and the mechanistic features (catalytic rate constants, substrate concentration, formal potentials), also paying attention to the SW components that are demonstrated to be remarkably helpful in the identification of the catalyst active form. Thus, the ability of the SWV technique for the elucidation of the catalytic species and pathways, and for the determination of the corresponding rate constants is assessed, establishing accurate and valuable diagnosis criteria and procedures for quantitative data analysis based on mathematical expressions that are rigorous and easy-to-implement, and that consider the influence of diffusion on the response.

Biomass valorization of walnut shell into biochar as a resource for electrochemical simultaneous detection of heavy metal ions in water and soil samples: Preparation, characterization, and applications

Lately, due to its accessibility and eco-friendliness, walnut shell biochar (WS-BC) is gaining attention as an electrode material component in the electrochemical detection of water pollutants. The overall performance of WS-BC is reliant on the nature of raw biomass and the production methods as well. In our concept, biochar, prepared from raw walnut shell (WS) by pyrolysis, was added to a carbon paste electrode (CPE), and poly-tyrosine (p-Tyr) was electrodeposited on the surface of the BC-doped electrode. The conditions of the elaboration of the electrode, such as pH, potential, and the number of deposition cycles, pH were optimized. The obtained p-Tyr-BC-CPE platform was tested for the determination of cadmium, lead, copper, and mercury ions in water and soil samples, using square wave voltammetry (SWV). The raw WS biomass and its BC were examined by thermal analysis (TG-DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) techniques. The synergistic effects of the coexistence of the WS-BC and the thin film of p-Tyr, for the detection of traces of heavy metal ions were investigated by electrochemical tests. The electrochemical characterization of the unmodified and modified electrodes was performed using the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods, while the Cd2+, Pb2+, Cu2+, and Hg2+ detection experiments were studied using the CV and SWV techniques. The optimized experimental conditions for the p-Tyr-BC-CPE platform were evaluated. The obtained electrochemical results showed that the p-Tyr-BC-CPE platform produced excellent sensitivity toward the heavy metal ions: LOD of 0.086, 0.175, 0.246, and 0.383 nM for Cd(II), Pb(II), Cu(II) and Hg(II), respectively. The modified electrode platform displayed high selectivity, stability, and good reproducibility.

Miniaturized 3D printed electrochemical platform with optimized Fibrous carbon electrode for non-interfering hypochlorite sensing.

3D printing technology based electrochemical device can provide ease of fabrication, cost effectiveness, rapid detection and lower limit of detection. Herein, a novel, customized, portable and inexpensive 3D printed electrochemical device, has been presented. Fibrous carbon Toray paper, deposited with gold nanoparticles through electrodeposition, used as a working electrode which Further device was tested with 1mM sodium hypochlorite using cyclic voltammetry (CV) and square wave voltammetry (SWV) in 0.1M PBS. Hypochlorite has a pivotal role in supporting the growing chemical and paper industries and finds diverse uses in several clinical applications. It is primarily used for disinfecting food, water and surfaces. The scan rate study was carried out from 20mVs-1 to 250mVs-1 using cyclic voltammetry technique. The diffusion coefficient obtained from scan rate effect was 1.39×10-6 cm2s-1. The concentration range was evaluated with SWV technique, in a linear range of 0.6μM-40μM, with a detection limit of 0.7μM. The device was further analyzed to ensure non-interference from co-existing chemicals like sodium chloride, potassium nitrate, sodium carbonate, sodium nitrite. Real sample analysis was done with sea, artificial sea and tap water with impressive recovery values. In summary, the developed working electrode can be customized and modified based on testing analyte; thus, the proposed device can be used for various other biochemical analytes.

Development of 2D graphene oxide sheets-based voltammetric sensor for electrochemical sensing of fungicide, carbendazim.

Incorporating new pollutants and environmental pollution has become a formidable issue as new pollutants are introduced into it and have become a significant concern in recent years. Detection of such pollutants needs a susceptible, selective, and cost-effective sensor that can sense their presence and quantify them at a trace level. In the present study, we have designed a 2D graphene oxide (GO)-based glassy carbon electrode (GCE) electrochemical sensor (GO/GCE) and utilized it as a sensing material for the detection and determination of CRZ. The voltammetric behavior of CRZ was studied using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. The SWV was applied to quantify and analyze CRZ in actual samples. A better response of CRZ was noticed at GO/GCE when phosphate buffer solution of pH 4.2 was used as a supporting electrolyte for to experiment. The SWV technique achieved trace-level detection of CRZ. A linearity plot was obtained for the concentration range of 1.0×10-7M to 2.5×10-4M with a limit of detection of 1.38×10-8M. The selectivity of the modified sensor was verified by the interference study of metal ions and other pesticides with CRZ. The agricultural and environmental significance of the developed method was successfully tested by estimating CRZ in water and soil samples.

Sensing of Alphacypermethrin Pesticide Using Modified Electrode of Chitosan-Silver Nanowire Nanocomposite Langmuir Blodgett Film

ABSTRACT We report on the sensing of a hazardous pesticide alphacypermethrin (ACM) using electrochemical technique through a nanocomposite film modified electrode. The nanocomposite film comprising of octadecylamine, chitosan, polyvinyl alcohol-silver nanowires and haemoglobin, shortly (OCPAH), was prepared by Langmuir–Blodgett (LB) film deposition technique on various substrates and electrodes. The composite LB film was characterised by UV-visible spectroscopy and scanning electron microscopy, which confirms the stable and multilayer film. The LB film modified electrode was used for sensing ACM pesticide by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) techniques. The achieved sensing parameters such as limit of detection as 14 nM, 5 nM and 10 nM; linear range as 10–100 nM, 10–40 nM and 50–100 nM/10–100 nM; and sensitivity as 0.418 µA/nM/cm2, 0.259 µA/nM/cm2 and 0.271 µA/nM/cm2 for CV, DPV and SWV techniques, respectively. The reported sensor is found to have stability of 74% upto 20 cycles, the relative standard deviation (RSD) value for metal ion/organic interference species as 2% and for real samples are within 1.4% using CV technique. The reported nanocomposite-based ACM pesticide sensor will open up new options for research on LB film nanocomposite-based sensing of different organophosphorus groups of pesticides.

Transdermal Polymeric Microneedle Sensing Platform for Fentanyl Detection in Biofluid.

Opioid drugs are extremely potent synthetic analytes, and their abuse is common around the world. Hence, a rapid and point-of-need device is necessary to assess the presence of this compound in body fluid so that a timely countermeasure can be provided to the exposed individuals. Herein, we present an attractive microneedle sensing platform for the detection of the opioid drug fentanyl in real serum samples using an electrochemical detection method. The device contained an array of pyramidal microneedle structures that were integrated with platinum (Pt) and silver (Ag) wires, each with a microcavity opening. The working sensor was modified by graphene ink and subsequently with 4 (3-Butyl-1-imidazolio)-1-butanesulfonate) ionic liquid. The microneedle sensor showed direct oxidation of fentanyl in liquid samples with a detection limit of 27.8 μM by employing a highly sensitive square-wave voltammetry technique. The resulting microneedle-based sensing platform displayed an interference-free fentanyl detection in diluted serum without conceding its sensitivity, stability, and response time. The obtained results revealed that the microneedle sensor holds considerable promise for point-of-need fentanyl detection and opens additional opportunities for detecting substances of abuse in emergencies.