Adsorptive Anodic Stripping Voltammetry Research Articles

Electrochemical determination of rosuvastatin calcium in pharmaceutical and human body fluid samples using a composite of vertically aligned carbon nanotubes and graphene oxide as the electrode material

A novel electrochemical method for the determination of rosuvastatin calcium (RC) using a composite of vertically aligned carbon nanotubes and graphene oxide (VACNT-GO) as the electrode material is proposed. The VACNT-GO electrode was synthesized using a microwave-assisted chemical vapor deposition method followed by oxygen plasma treatment. The VACNT-GO electrode presented superhydrophilic behavior and fast charge transfer, which are very attractive for electrochemical applications. The RC molecule presented an oxidation process at +1.26V vs. Ag/AgCl (3.0molL−1 KCl) in phosphate buffer solution (pH 2), and this redox behavior was explored for its voltammetric determination. Using square-wave adsorptive anodic stripping voltammetry (SWAdASV) under optimized conditions, the analytical curve was linear in RC concentration range from 0.48 to 46.72μmolL−1 with a limit of detection of 0.06μmolL−1. The developed SWAdASV method was applied for RC quantification in commercial pharmaceutical samples, and the results are consistent with those obtained by the comparative spectrophotometric method at a confidence level of 95%. Moreover, RC was determined in human body fluid samples of urine and human serum.

Indium oxide nanoparticles modified carbon paste electrode for sensitive voltammetric determination of aromatase inhibitor formestane

This paper reports a novel, simple and sensitive electrochemical method for the determination of formestane (FMT) in aqueous media (BR buffer solution, pH 5.2) on indium oxide nanoparticles modified carbon paste electrode (In2O3 NPs/CPE). The prepared In2O3 nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The fabricated In2O3 NPs/CPE displayed high effective surface area, more reactive sites and excellent electrochemical catalytic activity toward the oxidation of FMT. The voltammetric oxidation of FMT was studied at a carbon paste and indium oxide nanoparticles modified carbon paste electrodes by cyclic voltammetry and its determination was carried out by square wave anodic adsorptive stripping voltammetry (SWAASV). The electrochemical parameters such as surface concentration (Г), electron transfer coefficient (α), and the electron transfer rate constant (ks) of FMT at the modified electrode were calculated. Under the optimal conditions at In2O3 NPs/CPE, a linear relationship was realized between the anodic peak currents and FMT concentrations in the range of 0.19–2.91μM, with the detection limit of 6.2×10−8M. This modified electrode was used as a sensor for determination of FMT in blood serum and urine samples with satisfactory results.

Electrochemical determination of pipazethate hydrochloride on Na-montmorillonite modified carbon paste electrode in formulation and human blood

The electrochemical and interfacial adsorptive behavior of pipazethate HCl (PZ.HCl) onto the developed carbon paste electrode surface modified with sodium-montmorillonite clay (Na-MMT CPE) were investigated using cyclic voltammetry. Two validated adsorptive anodic stripping voltammetry methods have also been developed for its determination using 7 % (w/w) Na-MMT-modified CPE. Langmuir isotherm can describe the experimental data well, indicating monolayer adsorption. Limits of detection of 2.4 × 10−7 and 3.0 × 10−8 mol L−1 PZ.HCl were achieved in the bulk form using linear-sweep and square-wave adsorptive anodic stripping voltammetric methods, respectively. The developed methods were also successfully applied for determination of PZ.HCl in pharmaceutical formulation and in spiked human serum without time-consuming extraction steps prior to the analysis. Statistical comparison of the results of the proposed methods with that of official and reported spectrophotometric methods indicates no significant difference in precision and accuracy between the proposed and reference methods.

Electrochemical mediated preparation of chelating polymer brushes at paraffin-impregnated graphite electrode for Pb2+ sensing

In this work, two-dimension iminodiacetic acid functional gclycidyl methacrylate polymer brushes were prepared at paraffin-impregnated electrode for Pb2+ sensing. Gclycidyl methacrylate polymer brushes were prepared using electrochemical mediated atom transfer radical polymerization, ring-opening reaction of the epoxy groups was enforced using iminodiacetic acid to form chelating polymer brushes (IGMA/WGE). The electrode was carefully examined by fourier transform infrared spectroscopy, field emission scanning electronmicroscope and electrochemistry techniques. Abundant chelating polymer brushes evenly coated at WGE with an average size of 0.1×2μm. Further IGMA/WGE was successfully used for the determination of Pb2+ by differential pulse adsorptive anodic stripping voltammetry. The current responses (-0.58V) were linearly increased depending on the concentration from 3 to 90nM (i(μA)=-1.12+0.82 c (nM), limit 0.79nM, 3σ). The present electrode is potentially useful for real sample analysis.

Development of a carbon nanotube paste electrode modified with zinc phosphate for captopril determination in pharmaceutical and biological samples

We report a novel electrode composite comprising zinc phosphate within a multiwalled carbon nanotube paste electrode matrix which is applied for the detection of trace amounts of captopril (CAP) via square-wave adsorptive anodic stripping voltammetry (SWAdASV); to the best of our knowledge this is the first report on such a composite electrode. Under optimum experimental conditions, the peak current of CAP was found to be linear over the concentration range from 3.7 to 67 μmol L−1 with a limit of detection of 0.1 μmol L−1. The proposed method was applied for the successful determination of CAP in commercial tablet excipients and biological samples using the electroanalytical protocol evaluated against the laboratory standard iodometric procedure. Excellent comparability between the two is found suggesting that the former can replace the latter within laboratory settings or can be applied to in-the-field applications.

Voltammetric determination of verapamil and propranolol using a glassy carbon electrode modified with functionalized multiwalled carbon nanotubes within a poly (allylamine hydrochloride) film

In this report, we describe the individual determination of verapamil (VPM) and propranolol (PROP) in pharmaceutical formulations using square-wave adsorptive anodic stripping voltammetry (SWAdASV), differential-pulse adsorptive anodic stripping voltammetry (DPAdASV), and a glassy carbon electrode modified with functionalized multiwalled carbon nanotubes within a poly (allylamine hydrochloride) film. The anodic peak potential for VPM and PROP at this modified electrode was 1.09V and 0.930V (versus Ag/AgCl (3.0molL−1 KCl)), respectively, in a 0.25molL−1 H2SO4 solution. Under optimized SWAdASV and DPAdASV conditions, the obtained analytical curves were linear for VPM concentrations ranging from 5.0×10−9 to 1.1×10−7molL−1, and PROP concentrations ranging from 7.4×10−8 to 1.0×10−6molL−1, with detection limits of 3.6×10−9 molL−1 and 2.6×10−8molL−1, respectively. Both of the proposed methods were successfully applied for the individual determination of VPM and PROP in several pharmaceutical formulations. The results were in a close agreement with a 95% confidence level for those obtained using official spectrophotometric methods.

Ultrasonic preparation of tetraoxalyl ethylenediamine melamine resin-coated multiwalled carbon nanotubes for trace Ni(II) sensing

Under an aid of ultrasonic, tetraoxalyl ethylenediamine melamine resin-coated multiwalled carbon nanotubes were prepared for Ni(II) sensing in aqueous solution. The processes involved the fabrication of tetraoxalyl ethylenediamine melamine resin by one pot way, the coating of tetraoxalyl ethylenediamine melamine resin at multiwalled carbon nanotubes (MWCNTs), and the determination of Ni(II). The present materials were carefully examined by Fourier transform infrared spectroscopy, field emission scanning electron microscope, and electrochemistry techniques. A great deal of amorphous microsphere could be observed for tetraoxalyl ethylenediamine melamine resin with an average diameter of 1.2 μm, and MTE could evenly adhere at the surface of MWCNTs by the ultrasonic. Tetraoxalyl ethylenediamine melamine resin-coated multiwalled carbon nanotube-modified paraffin-impregnated graphite electrode was successfully used for the determination of Ni(II) by differential pulse adsorptive anodic stripping voltammetry. The current responses (−0.3 V) were linearly increased depending on the concentration from 1 × 10−11 to 3 × 10−10 M (i (μA) = 11.1 + 7.9 c (1 × 10−12 M); R = 0.9901, 3σ = 7 × 10−12 M).

Renewable Pencil Electrodes for Highly Sensitive Anodic Stripping Voltammetric Determination of 3‐Hydroxyflavone and Morin in Bulk Form and in Biological Fluids

AbstractAn electrochemical anodic adsorptive stripping procedure for ultra‐trace assay of 3‐hydroxyflavone (3HF) and Morin at a renewable pencil electrode (PGE) in bulk form and in biological fluids is described. The nature of the oxidation process of 3HF and Morin taking place at the PGE was characterized by cyclic voltammetry. The results show that the determination of the oxidation peak current is the basis of a simple, accurate and rapid method for quantification of 3HF by square‐wave anodic stripping voltammetry. Determination of Morin was achieved by square‐wave anodic adsorptive stripping voltammetry of the formed MorinCu(II) complex at a PGE. Factors influencing the trace measurements of 3HF and the MorinCu (II) complex at a PGE are assessed. The limits of detection and quantitation for the determination of 3HF and Morin in bulk form and in biological fluids were determined. The statistical analysis and the calibration curve data for trace determination of 3HF and Morin are reported.

Trace determination of vardenafil hydrochloride in commercial formulation and human serum by adsorptive anodic stripping voltammetry at a carbon paste electrode

The electrochemical behavior of vardenafil HCl (VRL) at a carbon paste electrode (CPE) was investigated by cyclic voltammetry, and the mechanism of its oxidation was suggested and discussed. A simple Nujol-based CPE in combination with a sensitive square-wave adsorption anodic stripping voltammetry method was described for trace determination of VRL. The described method showed excellent performance for trace determination of VRL in its formulation “Levitra® tablets” without interference from excipients. The results were statistically compared with those obtained with an established HPLC method; nonsignificant differences were found between the described voltammetric and HPLC methods. The described stripping voltammetric method is highly sensitive (limit of detection = 3 × 10−10 mol L−1 and limit of quantitation = 1 × 10−9 mol L−1). It was successfully applied for the determination of VRL in spiked human serum without the necessity for pretreatment and/or time-consuming extraction steps prior to the analysis.

Experimental and Theoretical Study on the Electrochemical Behavior of Zofenopril and its Voltammetric Determination

Electrochemical behavior of zofenopril (ZOF) was studied via experimental electrochemical methods and theoretical calculations performed at B3LYP/6-31+G(d)//AM1 level. Optimum conditions for quantitative determination were investigated by several electrochemical methods such as cyclic voltammetry, square-wave voltammetry and bulk electrolysis. Electrochemical parameters like charge transfer, diffusion and surface coverage coefficients of adsorbed molecules and also number of electrons transferred in electrode mechanisms were calculated. All studies were based on the irreversible and adsorption-controlled electrochemical oxidation signal of ZOF at about 1.1 V versus Ag/AgCl at pH 5.0 in Britton-Robinson buffer (BR). This adsorptive character of ZOF was used to develop fully validated, new, rapid, selective and simple voltammetric methods for the direct determination of the molecule in pharmaceutical dosage forms and biological samples without time-consuming steps prior to drug analysis. Peak current of electrochemical oxidation of ZOF was found to change linearly with the concentration in the range from 2.0x10-6 molL-1 (0.86 mgL-1) to 1.0x10-4 molL-1 (42.9 mgL-1) in direct voltammetric methods and found to change linearly with the concentration in the range from 2.0x10-8 molL-1 (8.59 μgL-1) to 1.0x10-6 molL-1 (0.43 mgL-1) in adsorptive stripping voltammetric methods. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 1.17x10-8 molL-1 (5.03 μgL-1) and 3.89x10-8 molL-1 (16.8 μgL-1) respectively in anodic adsorptive stripping voltammetry. The methods were successfully applied to assay the drug in tablets, human serum and human urine with good recoveries (between 95.0 % and 104.6 %) and relative standard deviation less than 10 %. Keywords: Adsorptive stripping voltammetry, AM1, Biological samples, DFT, HOMO-LUMO, Pharmaceuticals, Zofenopril

Determination of Hg(II) in natural waters using a carbon paste electrode modified with hybrid mesostructured silica nanoparticles

Mesostructured silica nanoparticles functionalized with a 5-mercapto-1-methyltetrazole derivative (MTTZ-MSU-2) were employed to prepare a chemically modified carbon paste electrode for Hg(II) determination in aqueous media by square wave adsorptive anodic stripping voltammetry. Under optimized operating conditions, 60s of electrolysis time in HCl 0.1M, the voltammetric signal increased with increasing preconcentration time from 1 to 10min. The voltammetric responses measured (peak areas) were linear with respect to Hg(II) concentration in the range of 0.1–1μM with a detection limit of 0.099μM after 5min preconcentration time and in the range of 0.025–0.25μM with a detection limit of 0.023μM for 10min of preconcentration time. The chemically modified carbon paste electrode had good single and inter-electrode reproducibility (RSD of 2 and 12%, respectively). Applicability to spiked groundwater and river water was demonstrated without any sample pretreatment (recoveries of 99 and 92%, RSD 4–7%, respectively).

Trace determination of zirconium by adsorptive anodic stripping voltammetry of its complex with alizarin violet using a glassy carbon electrode modified with acetylene black-dihexadecyl hydrogen phosphate composite film

We report on a novel electrochemical method for the sensitive determination of trace zirconium (Zr) at a glassy carbon electrode modified with a film of acetylene black containing dihexadecyl hydrogen phosphate and in the presence of alizarin violet (AV). The method is based on the preconcentration of the Zr(IV)-AV complex at a potential of −200 mV (vs. SCE). The adsorbed complex is then oxidized, producing a response with a peak potential of 526 mV. Compared to the poor electrochemical signal at the unmodified GCE, the electrochemical response of Zr(IV)-AV complex is greatly improved, as confirmed by the significant increase in peak current. The effects of experimental conditions on the oxidation current were studied and a calibration plot established. The oxidation current is linearly related to the Zr(IV) concentration in the 8.0 pM to 10 nM concentration range (cAV = 0.2 μM) and 10 nM ~0.6 μM (cAV = 2.0 μM), and the detection limit (S/N = 3) is as low as 4.0 pM for a 3-min accumulation time. The method was successfully employed to the determination of zirconium in standard ore samples.

A new electrochemical method for the determination of trace molybdenum(VI) using carbon paste electrode modified with sodium dodecyl sulfate

A sensitive procedure was developed for the determination of trace molybdenum(VI) by adsorptive anodic stripping voltammetry based on the oxidation of molybdenum(VI)–2′,3,4′,5,7-pentahydroxyflavone (morin) complex at a sodium dodecyl sulfate modified carbon paste electrode (denoted as SDS/CPE). Compared with the poor response at a conventional paste electrode, the electrooxidation of molybdenum(VI)–morin complex at the SDS/CPE was greatly improved, as confirmed from the significant enhancement of peak current and the negative shift of peak potentials. The optimum conditions for the analysis of molybdenum(VI) include 0.1 M sulfuric acid, 3.0 × 10 −5 M or 3.0 × 10 −6 M morin, an accumulation potential of −0.1 V (versus SCE), an accumulation period of 60 s or 120 s and a scan rate of 0.1 V s −1. Under the selected conditions, the linearity between peak currents and concentrations of molybdenum(VI) existed for a wide range of 8.0 × 10 −10–6.0 × 10 −8 M ( c morin = 3 × 10 −6 M) for 120 s accumulation and 6.0 × 10 −8–6.0 × 10 −6 M ( c morin = 3 × 10 −5 M) for 60 s accumulation, a low detection limit (three times signal to noise) of 4.0 × 10 −10 M was obtained after a 120 s preconcentration. The proposed method was successfully applied to the determination of molybdenum(VI) in real samples with enhanced selectivity.

Simultaneous detection of Ponceat 4R and tartrazine in food using adsorptive stripping voltammetry on an acetylene black nanoparticle‐modified electrode

Ponceau 4R and tartrazine have been widely used in foodstuffs. However, they are pathogenic if they are excessively consumed. Therefore, the detection of Ponceat 4R and tartrazine is quite important. A sensitive and rapid electrochemical method was developed for the simultaneous detection of Ponceat 4R and tartrazine using anodic adsorptive stripping voltammetry and based on the strong enhancement effect of acetylene black nanoparticle. For Ponceat 4R, the linear range was from 0.05 to 4 mg kg(-1) , and the limit of detection was 0.03 mg kg(-1) . For tartrazine, the linear range was from 0.15 to 18 mg kg(-1) , and the limit of detection was 0.1 mg kg(-1) . The relative standard deviation was 3.8% and 4.7% for 10 successive measurements of 1 mg kg(-1) Ponceau 4R and tartrazine. The method was used to determine Ponceat 4R and tartrazine in soft drinks, and recovery was in the range of 92.4-104.8%. At the acetylene black nanoparticle-modified electrode, the oxidation current signal of Ponceau 4R and tartrazine greatly increase. This new method is sensitive, rapid, simple and feasible.

Determination of Trace Aluminum by Anodic Adsorptive Stripping Voltammetry Using a Multi-Walled Carbon Nanotube Modified Carbon Paste Electrode

The adsorptive voltammetric behavior of the aluminum (Al)-alizarin violet (AV) complex in 0.2 mol L−1 HAc-NaAc buffer (pH 4.5) at a multi-walled carbon nanotube modified carbon paste electrode (MWCNT/CPE) was investigated. The results showed that the complex can be adsorbed on the surface of the MWCNT/CPE, yielding one oxidation peak at 530 mV (vs. SCE). The proposed method exhibits good linearity over the range from 1.0 × 10−9 mol L−1 to 1.0 × 10−7 mol L−1, and a low detection limit of 6.0 × 10−10 mol L-1 for 120 s accumulation was obtained under optimum conditions.

Stripping voltammetric determination of silymarin in formulations and human blood utilizing bare and modified carbon paste electrodes

Silymarin is one of the most powerful natural substances that have the ability to protect and rebuild the liver cells damaged by alcohol and other toxic substances. Silymarin showed two irreversible anodic peaks in buffered solutions (pH 2.5–8.0) at either the bare carbon paste electrode or the montmorillonite-Ca modified carbon paste one. These two peaks have been attributed to oxidation of the two phenolic OH groups at positions C-20 and C-7 of silymarin molecule. A square-wave adsorptive anodic stripping voltammetry method was optimized for determination of silymarin utilizing the bare and the modified carbon paste electrodes. The method was fully validated and successfully applied for the determination of silymarin in commercial formulations and human serum without prior extraction utilizing both carbon paste electrodes. Limits of quantitation of 1 × 10 −7 and 7 × 10 −9 mol L −1 silymarin have been achieved in bulk form or in formulations while 2 × 10 −7 and 8 × 10 −9 mol L −1 silymarin were achieved in spiked human serum utilizing the bare carbon paste electrode and the modified one, respectively. The two electrodes exhibited excellent selectivity towards silymarin even in the presence of 10 2to 10 3-fold excess of its co-formulated drugs, common excipients, and common metal ions. The pharmacokinetic parameters of silymarin in plasma of healthy human volunteers were estimated following the administration of a single oral dose of 120 mg silymarin utilizing the modified carbon paste electrode. The estimated pharmacokinetic parameters were favorably compared with those reported in literature.

Aluminium content in beers and silicon sequestering effects

Aluminium gives beer a metallic and bitter flavour without any observations on particular aroma compound changes. Besides it has lately been implicated as one of the possible causal factors contributing to Alzheimer's disease. A highly sensitive, selective, rapid, reliable and inexpensive method has been used for direct analysis of free aluminium in thirty-nine samples of bottled lager beer. Differential pulse adsorptive anodic stripping voltammetry (DPAdSV) technique at a hanging mercury drop electrode (HMDE) without any sample digestion was performed. Thirty nine different commercial beers (dark, pale and alcohol-free) were analysed. The aluminium content ranged between 3 and 15 ppb. The results show that in non-Spanish beers, the aluminium content in alcohol-free beers is lower than in dark and pale beers. Nevertheless, in the case of the national beers –Spanish–, no relation has been observed between the content of aluminium and the type of beer. Since beer also contains silicon which can affect the bioavailability of aluminium. Therefore, the moderate consumption of beer might affect the toxicokinetics of aluminium and thereby limit its neurotoxicity.

Determination of trace vanadium(V) by adsorptive anodic stripping voltammetry on an acetylene black paste electrode in the presence of alizarin violet

A sensitive and simplified voltammetric method is developed for the determination of trace amounts of vanadium(V) by adsorptive anodic stripping voltammetry using an acetylene black (AB) paste electrode. The method is based on the preconcentration of the V(V)–alizarin violet (AV) complex at open circuit while stirring the solution for 90 s in 0.15 mol dm −3 hexamethylenetetraamine–hydrochloric acid buffer (pH 4.4), the adsorbed complex is then oxidized, producing a response with a peak potential of 564 mV when scanning linearly from 0 to 1000 mV. For voltammetric determination of V(V), the parameters influencing the peak current have been optimized. Under the selected conditions, the peak current and concentration of V(V) accorded with linear relationship in the range of 8.0 × 10 −10 mol dm −3–1.0 × 10 −7 mol dm −3 ( c AV = 2.0 × 10 −6 mol dm −3) and 1.0 × 10 −7 mol dm −3–8.0 × 10 −6 mol dm −3 ( c AV = 2.0 × 10 −5 mol dm −3), the detection limit (three times signal to noise) was estimated to be 6.0 × 10 −10 mol dm −3 for 90 s accumulation. The relative standard deviation (RSD) is 1.9% and 2.3% for V(V) concentrations of 1.0 × 10 −7 mol dm −3 and 1.0 × 10 −8 mol dm −3 respectively. Finally, this proposed method was successfully applied to the determination of V(V) in natural water samples.

Determination of molybdenum by adsorptive anodic stripping voltammetry of molybdenum–alizarin violet complex at an acetylene black paste electrode

A reliable and sensitive procedure for the determination of trace levels of molybdenum by adsorptive anodic stripping voltammetry is proposed. The method is based on adsorptive accumulation of the molybdenum (Mo)–alizarin violet (AV) complex onto an acetylene black paste electrode (ABPE), followed by oxidation of the adsorbed species by voltammetric scan using a second-order derivative modulation. For voltammetric determination of molybdenum, the parameters influencing the peak current have been optimized. Under the selected conditions, the electrode demonstrated linear response over a wide range of Mo(VI) concentration (6.0 × 10 −9–1.0 × 10 −5 mol/L), the detection limit was 2.0 × 10 −9 mol/L ( S/ N = 3) for 120 s accumulation. The effects of potential interfering ions were studied, and it was found that the proposed procedure was free from most interferences. The method has been applied to the determination of molybdenum in plant foodstuffs, and satisfied results were obtained.

Differential Pulse Anodic Stripping Voltammetric Simultaneous Determination of Copper(II) and Silver(I) with Bis(2‐hydroxyacetophenone) Butane‐2,3‐dihydrazone Modified Carbon Paste Electrodes

AbstractThe behavior of a modified carbon paste electrode (CPE) for simultaneous determination of copper(II) and silver(I) by anodic adsorptive stripping voltammetry (ASV) was studied. The electrode was built incorporating the bis(2‐hydroxyacetophenone) butane‐2,3‐dihydrazone (BHAB) as a complexing agent to a Nujol‐graphite base paste. The resulting electrode demonstrated linear responses over the range of Cu(II) and Ag(I) concentrations 0.1–20 and 0.01–2.0 µM respectively. The relative standard deviation (RSD) for the determination of 5.0 µM of both metal ions were 2.9 and 3.1 % for Cu(II) and Ag(I), respectively. The method has been applied to the analysis of copper in wheat and barley seed samples and silver in developed radiological film.