Differential Pulse Adsorptive Voltammetry Research Articles

Electrochemical sensor based on a glassy carbon electrode modified with a 3D carbon nanoporous composite for the detection of paracetamol in pharmaceutical samples

With the continued appearance of new drugs, there is a growing interest in the development of new analytical tools to detect and quantify drugs using a simple and reliable way. In this work, we describe the development of an electrochemical sensor based on glassy carbon electrodes modified with a carbon tubular nanocomposite for the detection of paracetamol in pharmaceutical samples. Paracetamol shows a strong adsorption on the electrode surface, which makes possible its determination by adsorptive differential pulse voltammetry in 0.1 mol/L citrate–phosphate pH 5 buffer solution. Optimal conditions for dispersion of carbonaceous material and best conditions for surface adsorption of paracetamol were obtained from experimental designs based on response surface methodology. The high adsorption capacity of paracetamol on the 3D carbon nanoporous composite and the sensitivity of the electrochemical technique employed showed a synergistic effect that allowed reaching a detection limit of 30 nmol L− 1 (4.5 ppb). In addition, the reproducibility and the repeatability were 7 and 5 %, respectively. The paracetamol determination from pharmaceutical samples was performed without pre-treatment of samples. The values of paracetamol founded for different pharmaceutical samples were in a very good agreement with those values obtained from the same samples using HPLC. Therefore, the developed electrochemical sensor is a promising, inexpensive, and easy-to-use tool for the detection and quantification of paracetamol in pharmaceutical samples.

Chitosan/TiO2 nanoparticles modified carbon paste electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium as an anti-inflammatory drug

Diclofenac (sodium [o-(2,6-dichloroanilino) phenyl] acetate) belongs to the class of non-steroidal anti-inflammatory drugs and is widely used as a painkiller. In this paper, a new, simple and effective electrochemical sensor for the determination of diclofenac was developed by modifying the carbon paste electrode. The electrode was modified with chitosan, a biopolymer with excellent adsorptive properties, and TiO2 nanoparticles, a catalytically active material. The modification of the electrode provided larger surface area and improved the electrical conductivity, resulting in enhanced electrochemical detection of diclofenac at a pH of 5.0 using adsorptive differential pulse voltammetry. Under optimal working conditions, linear relationship between the oxidation peak current and the diclofenac concentration was obtained in two different ranges, from 0.2 to 10 μM and from 10 to 100 μM, with a detection limit of 0.013 μM. The proposed method was successfully applied for the determination of diclofenac in commercial tablets and synthetic urine samples. The fabricated chitosan/TiO2/carbon paste electrode, with an optimized voltammetric method, showed excellent analytical performance for diclofenac determination in terms of stability, low detection limit, high sensitivity, selectivity, as well as good reproducibility and repeatability of results. The obtained results suggest the potential for further utilization of the developed sensor for the simultaneous determination of a group of non-steroidal anti-inflammatory drugs.

Determination of Orange II and Sulfasalazine in Food, Tablets, Urine, Soil, and Water by In Situ Preparation of Nickel Hydroxide Nanoflakes/Magnetite Nanoparticles for Magnetic Solid-phase Extraction followed by Electrochemical Detection

Two new methods were developed for sub-nanomolar electrochemical detection of orange II and sulfasalazine. A hydrated Ni(OH)2/Fe3O4 phase was prepared in situ and used for enrichment of orange II and sulfasalazine. Thereafter, the nanosorbent phase was washed with the acidic solutions to release orange II and sulfasalazine before detection by adsorptive differential pulse voltammetry on a Pt electrode modified by carboxyl functionalized multi-walled carbon nanotubes and adsorptive square wave voltammetry on a glassy carbon electrode modified by freshly prepared gold nanoparticles/carboxyl functionalized multiwalled carbon nanotubes composite, respectively. The enrichment-detection methods provided limits of detection of 0.29 and 0.49 nmol L−1 for orange II and sulfasalazine, respectively. The linear working ranges for orange II and sulfasalazine were 0.5–10 and 5–80 nmol L−1. Also, the selectivity of the methods was investigated. No significant interferences were observed. The methods were successfully applied on the determination of orange II and sulfasalazine in food, tablets, urine, soil, and water samples. Furthermore, density functional theory was used to predict the most stable structures of the orange II and sulfasalazine complexes with the hydrated nickel hydroxide. In addition, experiments showed that the Sips isotherm was the most suitable for describing the adsorption of sulfasalazine by the nanosorbent.

Ultrasensitive electrochemical sensor for simultaneous determination of sumatriptan and paroxetine using molecular imprinted polymer/sol-gel/polyoxometalate/rGO modified pencil graphite electrode

Sumatriptan (SUM) and paroxetine (PRX) has been widely used as antimigraine and antidepressant. Due to the close relationship between these diseases, the possibility of simultaneous use of these drugs is high, so it is essential to determine these drugs simultaneously. Therefore, simultaneous determination of SUM and PRX were performed using adsorptive differential pulse voltammetry (AdDPV) technique by a modified pencil graphite electrode (PGE). The electrode modification was accomplished using molecular imprinted polymer, phosphotungstic acid (PWA) and reduced graphene oxide (rGO) composite. Coating of the reduced graphene oxide/phosphotungstic acid substrate was performed by the electrochemical single-step method, and the molecular imprinted polymer (MIP) was fixed on the electrode by the sol-gel matrix. The modified electrode represented a selective and sensitive sensor for the simultaneous measurement of SUM and PRX. The imprinting factor for SUM and PRX was obtained 3.15 and 3.3, respectively. The linear range was 0.02–3 and 0.005–2.2 μM, and the detection limit was calculated 4.0 and 0.7 nM for SUM and PRX, respectively. It was concluded that for simultaneous detection, the sensor has better analytical performances than the previously reported electrochemical sensors for each of these drugs. The sensor was successfully used to simultaneously determination of these drugs in real samples.

Ultrasensitive electrochemical determination of trace ceftizoxime using a thin film of Preyssler nanocapsules on pencil graphite electrode surface modified with reduced graphene oxide

An ultrasensitive electrochemical sensor for the selective voltammetric measurement of trace ceftizoxime (CFX) was described. Modification of a pencil graphite electrode (PGE) was first done with the reduced graphene oxide (r-GO) and, afterward, Preyssler nanocapsules (PNCs) were generated onto the r-GO/PGE. The surface morphology of the synthetic compounds has been evaluated using FT-IR, FE-SEM, TEM, and SEM techniques. Adsorptive differential pulse voltammetry (AdDPV), cyclic voltammetry (CV), chronocoulometry (CC) and electrochemical impedance spectroscopy (EIS) were employed to investigate the CFX electrochemical characteristic on the modified electrode (PNCs/r-GO/PGE). The electron transfer coefficient (α) between PNCs/r-GO and PGE was calculated using the obtained CV. Also, chronocoulometry experiments were performed in the absence and presence of CFX to calculate diffusion coefficient (D) and capacity of adsorption (ΓS) of CFX for PNCs/r-GO/PGE thin film. Under the optimized conditions, the calibration curve of the CFX has a linear concentration range from 1.0 × 10−11 to 3.0 × 10−8 M (R2 = 0.9993) and a detection limit of 1.8 pM. The developed electrochemical sensor shows greater sensitivity than the earlier reported techniques for the CFX measurement. The sensor was successfully utilized to determine the trace amounts of CFX in pharmaceutical and blood serum with suitable recoveries.

Fabrication of DNA/poly l-methionine-silver nanoparticles/pencil graphite electrode and its application to the determination of carboxin

In this study, a novel electrochemical biosensor is reported for carboxin detection based on the fabrication of the deoxyribonucleic acid/poly l-methionine-silver nanoparticles/pencil graphite electrode (DNA/PMT-AgNPs/PGE). The electrochemical response of carboxin on the DNA/PMT-AgNPs/PGE was measured using adsorptive differential pulse voltammetry (AdDPV). The electrochemical impedance spectroscopy studies showed lower Rct values for PMT-AgNPs/PGE and DNA/PMT-AgNPs/PGE compared to PGE, demonstrating their good conductivity and faster electron transfer rate. Also, the interaction of DNA with carboxin led to the better accumulation of carboxin on the electrode surface. The proposed biosensor afforded excellent selectivity for carboxin against other pesticides. According to the findings, the DNA/PMT-AgNPs/PGE presents a linear response over the carboxin concentration ranges from 8.0 pM to 1.0 µM. The detection limit was obtained as 5.0 pM under the optimized conditions. The applied DNA/PMT-AgNPs/PGE could successfully detect carboxin in the tap and river water.

Electrochemical determination of theophylline on a glassy carbon electrode modified with reduced graphene oxide-sodium dodecyl sulfate-Nafion composite film

An electrochemical sensor based on glassy carbon electrode modified with reduced graphene oxide-sodium dodecyl sulfate-Nafion* composite film was constructed and used to determine theophylline. The synthesized graphene oxide and surface morphology of the reduced graphene oxide-sodium dodecyl sulfate-Nafion film were characterized using IR spectroscopy, X-ray diffraction studies, and electrochemical impedance spectroscopy. The electrochemical behavior of the theophylline on the modified electrode was investigated using cyclic voltammetry and adsorptive differential pulse voltammetry. Under optimized analytical conditions, the electrode showed a linear response at concentrations of theophylline of 0.01–0.10, 0.1–1.0, and 1.0–40 µmol L−1 with the detection limit of 5 nmol L−1.

Electrochemical determination of dinitramine in water samples using a pencil graphite electrode modified with poly-l-cystein-gold nanoparticle

In this work, the electrochemical determination of dinitramine was performed by adsorptive differential pulse voltammetry (AdDPV) as a sensitive method and using a pencil graphite electrode modified with poly-l-cystein-gold nanoparticles (PLC-AuNPs/PGE). The field emission scanning electron microscopy (FESEM), electrochemical impedance spectroscopy (EIS), and energy-dispersive X-ray spectroscopy (EDX) were used to investigate the electrochemical characteristics of the electrodes. After optimization of different parameters, including number of cycles and scan rate for polymerization of l-cystein and entrapment of AuNPs, pH, adsorptive time, adsorptive potential of dinitramine and step potential (Estep) in the AdDPV method, the signal of oxidation of dinitramine was obtained which linearity increased over the concentration range from 1.0 × 10–9 to 1.0 × 10–8 M and 1.0 × 10–8 to 5 × 10–6 M. The detection limit was obtained as 1.83 × 10–10 M and relative standard deviation was calculated as 2.5% for determination of 2.0 μM dinitramine. The proposed method was used to determine dinitramine in tap (drinking) and river waters. This was a new strategy with excellent sensitivity, reproducibility and stability to measure dinitramine.

A metal-catex composite electrode for determination of paraquat in various samples by Ad-differential pulse cathodic stripping voltammetry

In this work, a novel kind of metal-catex composite electrode for determination of paraquat (PQ) by adsorptive differential pulse voltammetry is introduced. The metal-catex composite electrode was fabricated by cathodic electropolymerization of p-nitrophenol and p-nitrobenzoic acid in the presence of tin (II) chloride as a scaffold for composite structure on prepared glassy carbon electrode. Electropolymerization was carried out in sodium acetate medium. The surface of the fabricated electrode was characterized with field emission scanning electron microscope and energy-dispersive X-ray spectrometry. The obtained results show that there are Sn nanoparticles in the structure of the catex-composite. Chemical structure of metal-catex composite electrode was investigated using FTIR (ATR), 13C NMR, H NMR and a suitable mechanism for electropolymerization has been proposed. This metal-catex composite electrode was applied for determinations of PQ using sodium acetate buffer solutions at pH = 6.5 as an electrolyte solution. All parameters influencing the performance of the fabricated electrode were studied and optimized. The proposed electrode exhibits good linearity versus PQ concentration in the range of 3.8 × 10−8 to 7.7 × 10−7 mol L−1 and shows a manifold increase in sensitivity (more than 30 times) as compared to the glassy carbon electrode. The LOQ of this electrode was 7.78 × 10−9 mol L−1, which is comparable with that of other electrochemical methods. The mean, standard deviation and relative standard deviation for seven repetitive determinations of paraquat (7.78 × 10−8 mol L−1) were measured to be 7.75 × 10−8 mol L−1, ±0.29 × 10−8 mol L−1, and 3.75% respectively. This electrode was applied for the determination of paraquat in natural water, natural juice, potatoes and onions. The introduced electrode shows good stability with repeated use and over long periods (about 20 days). There is a good agreement between the results for water analysis by this method and the standard method.

Easy Activation of Pencil Graphite Electrode as Sensing Platform for Determination of Bisphenol A

The presented study focuses on the optimum conditions for chemical activation of pencil graphite electrodes (PGE) used in the determination of bisphenol A (BPA). The prepared ethanol–HCl mixture for chemical activation of pencil graphite electrode exhibits better activation factor compared with traditional activation methods like anodizing. The obtained porous and highly conductive surface of PGE can be used as a sensing device. The electrochemical behavior of BPA at the modified sensor was investigated. The effects of pH, accumulation time and sensor activation were examined. In the optimum experimental conditions, adsorptive differential pulse voltammetry was used for determination of BPA, which exhibits a linear calibration graph of Ip versus BPA concentration in the range 1.25 × 10–8 to 1.34 × 10–4 M. The calculated detection limit for S/N = 3 was 1.0 nM. The presented sensor is reusable. The activated PGE was applied for the determination of BPA leached from baby bottles as a real sample using spike method.

Adsorptive Voltammetry for the Determination of Ochratoxin A Using Enrichment Effect by Cationic Surfactants

AbstractA rapid and simple electrochemical method was utilized for the determination of the presence of classic fungal metabolite ochratoxin A (OTA) based on differential pulse adsorptive voltammetry, using the carbon nanotube paste (CNTP) electrode. OTA showed a clear oxidation peak, and the CNTP electrode exhibited a more sensitive response to OTA oxidation than the glassy carbon, the plastic formed carbon, and the carbon paste electrodes. The addition of long‐chain cationic surfactants, such as benzethonium chloride, cetyltrimethylammonium bromide, and benzyldimethyltetradecylammonium chloride (zephiramine), enhanced the electrochemical response of OTA. Under optimized experimental conditions, the calibration plots are linear in the 5×10−6−5×10−5 M OTA concentration range, and the limit of detection is 1.1×10−6 M. In order to improve the selectivity for OTA determination, we attempted to combine this adsorptive stripping voltammetric technique with “sequestration electrochemistry,” based on the specific interaction occurring between bovine serum albumin (BSA) and OTA. The peak current of OTA oxidation decreased substantially as a result of OTA‐BSA binding. Furthermore, it was demonstrated that the application of this proposed method of hydrodynamic adsorptive voltammetry, using a micro‐droplet and a rotating disk electrode, improves the approach's sensitivity and reduces the time and sample volume required for the analysis.

Ultrasensitive determination of ceftizoxime using pencil graphite electrode modified by hollow gold nanoparticles/reduced graphene oxide

In this work, a pencil graphite electrode (PGE) was modified using electrochemically reduced graphene oxide (rGO) and then hollow gold nanoparticles (HGNPs) were generated onto rGO/PGE by electrodeposition of cobalt and after that galvanic displacement reaction of cobalt nanoparticles with Au3+ ions. In this way, hollow gold nanoparticles/reduced graphene oxide/pencil graphite electrode (HGNPs/rGO/PGE) was constructed and used for sensitive voltammetric determination of ceftizoxime (CFX). The design experiment as a central composite design (CCD) methodology was developed as the experimental strategy for optimization of the influence of variables on the performance of modified electrode. The modified electrode was characterized using electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and choronocoulometry. The cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV) methods were utilized to survey the electrochemical action of CFX on the modified electrode. The linear dynamic range was 1.0×10-12M to 1.0×10-11M and 1.0×10-11M to 1.0×10-9M with a detection limit of 3.5 × 10−13 M. The existent method was employed to the determination of CFX in pharmaceutical and biological samples.

Electrochemical sensor for ultrasensitive determination of ceftazidime using hollow platinum nanoparticles/reduced graphene oxide/pencil graphite electrode

In this paper, an electrochemical sensor was prepared based on the modification of pencil graphite electrode (PGE) by hollow platinum nanoparticles/reduced graphene oxide (HPtNPs/rGO/PGE) for determination of ceftazidime (CFZ). Initially, rGO was electrodeposited on the electrode surface, and then, hollow platinum nanoparticles were placed on the electrode surface via galvanic displacement reaction of Pt(IV) ions with cobalt nanoparticles (CoNPs) that had electrodeposited on the electrode surface. Several significant parameters controlling the performance of the HPtNPs/rGO/PGE were examined and optimized using central composite design as one optimization methodology. The surface morphology and elemental characterization of the bare PGE, rGO/PGE, CoNPs/rGO/PGE, and HPtNPs/rGO/PGE-modified electrodes was analyzed by field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electrochemical impedance spectroscopy. The electrochemical activity of CFZ on resulting modified electrode was investigated by cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV). Adsorptive differential pulse voltammetry indicates that peak current increases linearly with respect to increment in CFZ concentration. CFZ was determined in the linear dynamic range of 5.0 × 10−13 to 1.0 × 10−9 M, and the detection limit was determined as 2.2 × 10−13 M using AdDPV under optimized conditions. The results showed that modified electrode has high selectivity and very high sensitivity. The method was used to determine of CFZ in drug injection and plasma samples.

Very sensitive electrochemical determination of diuron on glassy carbon electrode modified with reduced graphene oxide–gold nanoparticle–Nafion composite film

In this work, a very sensitive electrochemical sensor based on glassy carbon electrode (GCE) modified with reduced graphene oxide–gold nanoparticles/Nafion (rGO–AuNPs/Nafion) composite film was applied to determine diuron. Synthesized GO was characterized using X-ray diffraction (XRD) and UV–visible spectroscopy. The surface morphology of the rGO–AuNPs/Nafion film was also characterized using scanning electron microscopy and electrochemical impedance spectroscopy. Cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV) were applied to investigate the electrochemical response of the diuron on the modified electrode. The electrode showed a linear response at 1.0×10−9−1.0×10−7 M and a detection limit of 0.3nM under the optimized conditions. The effect of some other species on the determination of diuron was investigated and the sensor showed good selectivity for determination of diuron. The constructed sensor was applied to determine diuron in enriched samples of orange juice, mineral and tap water which statistical t-test showed accuracy of method. Also the sensor was applied to obtain diuron content in the tea sample. The reliability of the proposed sensor was confirmed after comparing the results with those obtained using high performance liquid chromatography (HPLC) as a comparative method.

Electrochemical determination of aminopyrene on glassy carbon electrode modified with multi-walled carbon nanotube–sodium dodecyl sulfate/Nafion composite film

A glassy carbon electrode (GCE) modified with multi-walled carbon nanotube–sodium dodecyl sulfate/Nafion (MWCNT–SDS/Nafion) composite film was constructed and used to determine 1-aminopyrene (1-AP). The surface morphology of the MWCNT–SDS/Nafion film was characterized using scanning electron microscopy and electrochemical impedance spectroscopy. The electrochemical behavior of the 1-AP on the modified electrode was investigated using cyclic voltammetry and adsorptive differential pulse voltammetry. After optimization of analytical conditions, the electrode showed a linear response at 0.04–0.40, 0.40–40.0 and 40.0–160nM and a detection limit of 0.02nM.

Simultaneous determination of mycophenolate mofetil and its active metabolite, mycophenolic acid, by differential pulse voltammetry using multi-walled carbon nanotubes modified glassy carbon electrode

A highly sensitive electrochemical sensor for the simultaneous determination of mycophenolate mofetil (MPM) and mycophenolic acid (MPA) was fabricated by multi-walled carbon nanotubes modified glassy carbon electrode (MWCNTs/GCE). The electrochemical behavior of these two drugs was studied at the modified electrode using cyclic voltammetry and adsorptive differential pulse voltammetry. MPM and MPA were oxidized at the GCE during an irreversible process. DPV analysis showed two oxidation peaks at 0.87V and 1.1V vs. Ag/AgCl for MPM and an oxidation peak at 0.87V vs. Ag/AgCl for MPA in phosphate buffer solution of pH5.0. The MWCNTs/GCE displayed excellent electrochemical activities toward oxidation of MPM and MPA relative to the bare GCE. The experimental design algorithm was used for optimization of DPV parameters. The electrode represents linear responses in the range 5.0×10−6 to 1.6×10−4molL−1 and 2.5×10−6molL−1 to 6.0×10−5molL−1 for MPM and MPA, respectively. The detection limit was found to be 9.0×10−7molL−1 and 4.0×10−7molL−1 for MPM and MPA, respectively. The modified electrode showed a good sensitivity and stability. It was successfully applied to the simultaneous determination of MPM and MPA in plasma and urine samples.

Electrochemical investigation of clozapine at TiO2 nanoparticles modified carbon paste electrode and simultaneous adsorptive voltammetric determination of two antipsychotic drugs

A new carbon paste electrode chemically modified with TiO2 nanoparticles (TiO2NP-MCPE) is constructed and used for the selective and sensitive electrochemical determination of trace amounts of clozapine (CLZ). The effect of carbon paste composition, working solution pH and scan rate were studied with this modified electrode. The presence of TiO2 nanoparticles in the carbon paste increased the available surface area of the electrode and improved the sensitivity by enhancing peak currents. The electrochemical behavior of the modified electrode and the mechanism of the oxidation of CLZ were investigated using cyclic voltammetry (CV). From the slope of the Tafel plot the α value was found 0.57. Using adsorptive differential pulse voltammetry (AD-DPV) at optimum parameters a linear dynamic range of 0.5–45μM clozapine was observed with detection limit of 61.0nM. In addition, the CLZ and thioridazine were determined simultaneously using TiO2NP-MCPE in AD-DPV. In AD-DPV measurements, used TiO2NP-MCPE, the oxidation peak potentials of CLZ and thioridazine was separated about 260mV. The voltammograms showed two anodic peaks at 370 and 630mV vs. Ag/AgCl, corresponding to the oxidation of CLZ and thioridazine, respectively. Finally, this method was used for determination of CLZ in clozapine tablets with satisfactory results.

Electroanalysis of some nitro-compounds using bulk bismuth electrode

Nitro compounds were usually determined electrochemically using the mercury drop with DPP technique. An alternate way to toxic mercury is the increasing use of the bismuth electrode as thin film electrodeposited on glassy carbon or copper for example, or as bulk bismuth disc. In the present paper several nitrocompounds were investigated: mononitrophenols, dinitrophenol, nitrobenzoic acid, nitrobenzaldehyde and a well known pesticide, parathion, which has a nitro group in para position on a phenyl cycle. Bulk bismuth electrode was a disc (cross section of a rod of 5 mm diameter embedded in Teflon®) polished with silicon carbide disc (P2400) and sonicated to remove any abrasive particle. The supporting electrolyte was the acetic buffer (pH 4.7), which was found suitable for all these compounds. Using cathodic sweep differential pulse voltammetry, it was noticed that according to the position of the nitro group on the cycle, the peak potentials might range between −300 to −750 mV vs. SCE. Limits of detection (LOD) and limits of quantification (LOQ) were determined for each compound whose response for increasing concentration was linear in the ∼3–50 µmol L−1 whatever the considered molecule. Adsorptive differential pulse voltammetry was found very efficient to determine parathion, because this molecule adsorbs on bismuth at −0.2 V vs. SCE. Bulk bismuth electrode was compared to the hanging mercury drop electrode and led to an identical behaviour.

β-Sonogel-Carbon electrodes: A new alternative for the electrochemical determination of catecholamines

In this work, a new alternative for the electrochemical determination of catecholamines based on β-cyclodextrin-Sonogel-Carbon electrodes is reported. The incorporation of β-CD and graphite in the preparation of the Sonogel-Carbon material leads to a modification of the electrode surface properties which causes a significant increase in the oxidation peak current of biomolecules such as dopamine, l-epinephrine, d, l-norepinephrine and catechol. This phenomenon might be attributed to the formation of an inclusion complex between β-CD and the catecholamines. The amount of β-CD necessary to form the Sonogel electrode was studied and optimization of electrochemical parameters, perm selectivity and mechanical stability of the sensor are discussed. Scanning electron microscopy and electrochemical impedance spectroscopy measurements were employed to characterize the electrical parameters and the structural properties of the new electrode surface, respectively. Cyclic voltammetry (CV) and Adsorptive differential pulse voltammetry (AdDPV) measurements were also used to explore the electrochemical behaviour of the electrode versus the quoted catecholamines. The β-CD-Sonogel-Carbon electrode offers fast and linear responses towards dopamine, norepinephrine, epinephrine and catechol, with good and low detection limits: 0.164, 0.294, 0.699 and 0.059 μmol L −1, respectively.

Determination of Diclofenac in Urine Samples by Molecularly‐Imprinted Solid‐Phase Extraction and Adsorptive Differential Pulse Voltammetry

AbstractA molecularly imprinted polymer for diclofenac (DCF) was prepared by thermal polymerization over silica beads using 2‐(dimethylamino)ethyl‐methacrylate as functional monomer. After silica elimination by HF treatment, the polymer was applied to the selective solid‐phase extraction of the drug from urine followed by its quantification by adsorptive differential pulse voltammetry. Results indicate that the drug could be selectively extracted from the sample and quantified at clinically relevant concentrations (μg/mL).