Determination of Captropril using adsorptive cathodic differential pulse stripping voltammetry with the HMDE

A voltammetric method for the determination of 3-mercapto-D-2-methylpropanoyl-L-proline, a hypotensive drug whose pharmaceutical name is Captopril (CPT), in the concentration range from 9.0×10⁻¹⁰M to 3×10⁻⁶M, is described. In this range the peak current increases linearly with drug concentration even when different collection periods are used. A self-cleaning Hanging Mercury Drop Electrode (HMDE) was used and a negative Differential Pulse potential (DP) was applied to the indicator electrode. The stripping peak of CPT splits into two peaks as soon as the concentration is increased over about 10⁻⁵M; in the oxidation DP scan, instead, this splitting is observed at a concentration of 2.0×10⁻⁴M. Some attempts were made to verify the suitability of other techniques such as Alternating Current polarography (AC) and the use of a different electrode, the Wax-Impregnated Graphite Electrode (WIGE).     

Determination of zinc by square-wave adsorptive stripping voltammetry using alizarin as a chelating agent

The adsorptive collection of zinc(II) complex with alizarin ligand, coupled with the square-wave voltammetric technique at the hanging mercury drop electrode, yields a very sensitive electroanalytical procedure for the determination of zinc. The optimized experimental conditions include: supporting electrolyte (carbonate buffer), pH (11), alizarin concentration (1 × 10^?6 mol l^?1), accumulation time (60 s), accumulation potential (?0.1 V), scan rate (700 mV s^?1), pulse amplitude (0.06 V) and SW frequency (80 Hz). The monitored stripping voltammetric current was linear over the range of 5 × 10^?8 – 4 × 10^?7 mol l^?1 and the detection limit was 1 × 10^?8 mol l^?1. The relative standard deviation was calculated as 1.3% (n = 10) for 1 × 10^?8 mol l^?1 Zn(II) and the obtained electrochemical signal was stabile for up to 60 min. Possible interferences by either co-existing metal ions or other chelating agents were also investigated. The applicability of the proposed SW-AdSV method to the analysis of foodstuff was assessed by the determination of zinc content in instant coffee samples. The accuracy of the obtained voltammetric analytical results was validated by comparing with that obtained by atomic absorption spectrometric method and conducting the necessary statistical evaluation.     

Determination of trace amounts of estriol and estradiol by adsorptive cathodic stripping voltammetry.

Estriol and estradiol are electroinactive in the potential range from -200 to -1000 mV versus a silver-silver chloride electrode at a mercury electrode. The conversion of these estrogens into electroactive nitro derivatives of estrogens, which are used for voltammetric determination, was studied. Such nitro derivatives give a well defined cathodic stripping wave at -600 mV in pH 10.5 borate buffer. Estriol and estradiol are determined in the ranges 1 x 10(-9)-1.5 x 10(-6) and 5 x 10(-9)-2 x 10(-6) mol dm-3, respectively, by differential-pulse adsorptive stripping voltammetry at a hanging mercury drop electrode. Some steroids, such as estrone, interfere because the three estrogens have almost the same molecular structure and have similar nitro derivatives, but progesterone does not interfere and is reduced at significantly more negative potentials than the nitrated estrogens. It can be determined simultaneously with estriol or estradiol. A method was developed for the assay of estriol in pharmaceutical preparations.     

Determination of trace amounts of morphine in human plasma by anodic adsorptive stripping differential pulse voltammetry

New adsorptive anodic differential pulse stripping voltammetry method for the direct determination of morphine at trace levels in human plasma of addicts is proposed.The procedure involves an adsorptive accumulation of morphine on a HMDE,followed by oxidation of adsorbed morphine by voltammetry scan using differential pulse modulation.The optimum conditions for the analysis of morphine are pH 10.5,Eacc of -100 mV（vs.Ag/AgCl）,and tacc of 120 s.The peak current is proportional to the concentration of morphine,and a Linear calibration graph is obtained at 0.01-3.10μg mL^-1.A relative standard deviation of 1.06%（n=5）was obtained,and the limit of detection was 3 ng mL^-1.The capabiLity of the method for the analysis of real samples was evaluated by the determination of morphine in spiked human plasma and addicts human plasma with satisfactory results.     

Determination of trace amounts of thallium by adsorptive cathodic stripping voltammetry with xylenol orange.

Trace amounts of thallium(I) can be determined using adsorptive cathodic stripping voltammetry in the presence of Xylenol Orange (XO). The reduction current of the thallium(I)-XO complex ion was measured by square-wave cathodic stripping voltammetry. The peak potential was at -0.44 V vs. Ag/AgCl. The effect of various parameters (pH, ligand concentration, accumulation potential and collection time) on the response are discussed. The response was linearly related to the thallium concentration in the range 0.5-110 ng ml(-1) and 110-2000 ng ml(-1). The limit of detection was 0.2 ng ml(-1). The relative standard deviation for the determination of 80 ng ml(-1) thallium was 2.8%. Many common anions and cations did not interfere with the determination of thallium. The interference of lead was reduced by the addition of 0.003 M sodium carbonate. The voltammetric procedure was then successfully applied to the determination of thallium in various complex samples.     

Determination of trace europium by adsorptive cathodic stripping voltammetry after complexation with cupferron

This article describes the determination of Eu by adsorptive cathodic stripping voltammetry after complexation with N-nitroso-N-phenylhydroxylamine (cupferron). The accumulation of the complex at the HMDE was performed at 0.0 V and the subsequent potential scan was made in the square wave mode. The analyte signal occurred at −0.88 V. The detection limit is 0.06 nmol dm⁻³. The effect of instrumental and chemical parameters on the peak height and potential was investigated. The same technique can be used for the determination of ytterbium and of the other rare earth elements (REEs) after separation.     

Determination of Bentazepam by differential pulse polarography and adsorptive stripping voltammetry

Summary A method is described for the determination of Bentazepam using DPP and ADSV with DP. Bentazepam is determined in buffer Britton-Robinson 0.04 mol l^-1 at pH 9 with detection limits of 3.1×10^-9 mol/l and a relative standard deviation of 0.8 DPP was used to determine Bentazepam in Tiadipona, the commercial product. ADSV was used to determine Bentazepam in urine with a detection limit of 2.7 ng ml^-1 (accumulation time 5 min) and a relative standard deviation of 1.5%.     

Simultaneous determination of trace amounts of nickel, cobalt, and zinc in the wastewater of a galvanic workshop by using adsorptive cathodic stripping voltammetry

Electroplating of Ni, Co, and Zn is widely used in the industry, because coating of tools with these materials can improve mechanical and chemical properties such as hardness, toughness, and corrosion resistively. Ni, Co, and Zn are among toxic metals of significance for environmental surveillance. Therefore, determination of these elements in wastewater is very important. This paper reports the use of an adsorptive cathodic stripping voltammetric technique for the simultaneous determination of Ni(II), Co(II), and Zn(II) with dimethylglyoxime (DMG) as a chelating agent. Voltammograms of Ni(II), Co(II), and Zn(II) initially contained three peaks corresponding to these metals. However, the peaks overlapped. Therefore, the effect of organic solvents was studied, and the results showed that the use of a suitable ratio of ethanol-water (1:5) solvent and pH provided peaks that were distinctly separated. The metals can be quantified at concentrations above 0.03 (Ni), 0.02 (Co), and 0.1 μg/mL (Zn). The RSD (%) at concentration levels of 0.10 μg/mL Ni(II), 0.10 μg/mL Co(II), and 0.30 μg/mL Zn(II) is 2.3, 2.0, and 3.3%, respectively. The influence of pH, DMG concentration, scan rate, accumulations time, and potential was investigated. The method was satisfactorily used for determination of the metals under study in water and wastewater. The text was submitted by the authors in English.     

Simultaneous determination of trace amounts of cadmium, nickel and cobalt in water samples by adsorptive voltammetry using ammonium 2-amino-cyclopentene dithiocarboxylate as a chelating agent

This paper reports the use of an adsorptive voltammetric technique for the simultaneous detection of Cd(II), Ni(II) and Co(II) using ammonium 2-amino-cyclopente dithiocarboxylate as a selective complexing agent. Scans containing three resolved peaks corresponding to these metals were obtained in synthetic and real samples. The reduction current peaks of the metals that were distinctly separated by 200 mV or more, allowing their determination over a wide range of concentrations. These metals can be quantified at concentrations above 1.33x10(-8) mol dm(-3) Cd(II), 8.51x10(-9) mol dm(-3) Ni(II) and 3.39x10(-10) mol dm(-3) Co(II). The influence of pH, ligand concentration, scan rate, accumulations time and applied potential was investigated. The R.S.D. at a concentration level of 1.78x10(-7) mol dm(-3) of Cd(II), 3.40x10(-7) mol dm(-3) and Ni(II) and 1.7x10(-9) mol dm(-3) of Co(II) was 2.5% for Cd(II), 2.7% for Ni(II) and 3.3% for Co(II). The method was applied to various water samples.     

Determination of the pesticide Chlorpyrifos by cathodic adsorptive stripping voltammetry

The adsorption behavior and differential pulse cathodic adsorptive stripping voltammetry of the pesticide Chlorpyrifos (CP) were investigated at the hanging mercury drop electrode (HMDE). The pesticide was accumulated at the HMDE and a well-defined stripping peak was obtained at –1.2 V vs Ag/AgCl electrode at pH 7.50. A voltammetric procedure was developed for the trace determination of Chlorpyrifos using differential pulse cathodic adsorptive stripping voltammetry (DP-CASV). The optimum working conditions for the determination of the compound were established. The peak current was linear over the concentration range 9.90 × 10^–8– 5.96 × 10^–7 mol/L of Chlorpyrifos. The influence of diverse ions and some other pesticides was investigated. The analysis of Chlorpyrifos in commercial formulations and treated waste water was carried out satisfactorily     

Determination of the pesticide Chlorpyrifos by cathodic adsorptive stripping voltammetry

The adsorption behavior and differential pulse cathodic adsorptive stripping voltammetry of the pesticide Chlorpyrifos (CP) were investigated at the hanging mercury drop electrode (HMDE). The pesticide was accumulated at the HMDE and a well-defined stripping peak was obtained at –1.2 V vs Ag/AgCl electrode at pH 7.50. A voltammetric procedure was developed for the trace determination of Chlorpyrifos using differential pulse cathodic adsorptive stripping voltammetry (DP-CASV). The optimum working conditions for the determination of the compound were established. The peak current was linear over the concentration range 9.90 × 10^–8– 5.96 × 10^–7 mol/L of Chlorpyrifos. The influence of diverse ions and some other pesticides was investigated. The analysis of Chlorpyrifos in commercial formulations and treated waste water was carried out satisfactorily Received: 10 July 1997 / Revised: 1 April 1998 / Accepted: 6 April 1998     

Determination of ultra trace amount of enrofloxacin by adsorptive cathodic stripping voltammetry using copper(II) as an intermediate

In this work, a simple and sensitive electroanalytical method was developed for the determination of enrofloxacin (ENRO) by adsorptive cathodic stripping voltammetry (ADSV) using Cu(II) as a suitable probe. The complex of copper(II) with ENRO was accumulated at the surface of a hanging mercury drop electrode at −0.10 V for 40 s. Then, the preconcentrated complex was reduced and the peak current was measured using square wave voltammetry (SWV). The optimization of experimental variables was conducted by experimental design and support vector machine (SVM) modeling. The model was used to find optimized values for the factors such as pH, Cu(II) concentration and accumulation potential. Under the optimized conditions, the peak current at −0.30 V is proportional to the concentration of ENRO over the range of 10.0-80.0 nmol L⁻¹ with a detection limit of 0.33 nmol L⁻¹. The influence of potential interfering substances on the determination of ENRO was examined. The method was successfully applied to determination of ENRO in plasma and pharmaceutical samples.     

Determination of dissolved manganese in natural waters by differential pulse cathodic stripping voltammetry

A procedure based on differential pulse cathodic stripping voltammetry on the graphite electrode is described for the determination of dissolved manganese in natural waters buffered at pH about 6.5 with acetate solution. In order to avoid interference of iron(II) the addition of fluoride is used. The limit of detection is 3 g/l for a deposition time of 6 min. Acidification and UV-irradiation are recommended for samples containing dissolved organic matter. Results of manganese determination in table mineral waters are reported and the possibility of manganese speciation is discussed.     

Determination of trace procaine hydrochloride by differential pulse adsorptive stripping voltammetry with a Nafion modified glassy carbon electrode.

A sensitive and selective method for the determination of procaine hydrochloride with a Nafion-modified glassy carbon electrode has been developed. The voltammetric behavior of procaine hydrochloride on the Nafion-modified electrode indicated that the modified electrode not only increased the sensitivity of the determination of procaine hydrochloride, but also catalyzed the electrode process. Procaine hydrochloride was accumulated in Britton-Robinson buffer (pH 2.09) at a potential of -0.2 V (vs. SCE) for 180 s, and was then determined by differential pulse adsorptive stripping voltammetry. The effect of various parameters, such as the pH of the medium, the mass of drop-coated Nafion, the accumulation potential, the accumulation time and the scan rate, were investigated. Under the optimum conditions, a linear calibration graph was obtained in the concentration range of 6.0 x 10(-8) to 6.0 x 10(-6) mol l(-1) with a correlation coefficient of 0.9987. The relative standard deviation was 4.18% for eight successive determinations of 1.0 x 10(-7) mol l(-1) procaine hydrochloride, and the detection limit (three times signal to noise) was 7.0 x 10(-9) mol l(-1). A study of interfering substances was also performed, and the method was applied to the direct determinations of procaine hydrochloride in the injection solution of procaine hydrochloride and in rabbit serum.     

Determination of selenium in sea water by adsorptive cathodic stripping voltammetry

A procedure is presented for determining Se(IV) and total dissolved Se in sea water using cathodic stripping voltammetry in the presence of added copper. Experiments using cyclic voltammetry indicate that the preconcentration step consists in adsorption of a Cu(I)₂Se complex species on the hanging mercury drop electrode. The optimized analytical conditions include a copper concentration of 40 μM and a solution pH of 1.6. Differential pulse modulation is used. Interference caused by organic surface-active substances present in natural waters in eliminated by UV photolysis of the sample. Cadmium interferes with the determination of Se only when present at a concentration 100 times higher than normal. UV photolysis at pH ≈ 8 is used to convert Se(VI), which is the electroactive species. The response is linear for Se concentrations between 0 and 200 nM. The limit of detection is 0.01 nM Se when a deposition time of 15 min is used.     

Determination of aluminium in tree samples by cathodic adsorptive stripping voltammetry

This paper presents a method of determination of aluminium in tree samples (wood, leaves, roots) based on the cathodic adsorptive stripping voltammetry. Al(III) complexed with alizarin S was determined by ASV method using a hanging mercury drop electrode. Optimal conditions were found to be: accumulation time 30-90 s, accumulation potential - 0.70 V versus SCE, supporting electrolyte 0.1 M ammonia-ammonium chloride buffer at pH 8.2 and concentration of alizarin 1 x 10(-5) M. The response of the system, a linear current-concentration relationship was observed up to 8 x 10(-6) M. The developed method has been tested by analysing international reference materials (BCR 62 Olive leaves and BCR 101 spruce needles).     

微分脉冲阴极溶出伏安法测定呋喃唑酮

研究了呋喃唑酮在玻碳电极上的伏安行为。在 1mol LHCl底液中 ,用微分脉冲阴极溶出伏安法得到一灵敏的呋喃唑酮还原峰 ,峰电位为 0 .0 38V(vs.Ag AgCl)。峰电流与呋喃唑酮浓度在 8× 1 0 -6～ 1× 1 0 -4 mol L范围内呈线性关系 (r=0 .9984) ,检出限为 8× 1 0 -8mol L。该法已用于片剂与合成血清样品中呋喃唑酮含量的测定     

Bismuth film electrodes for adsorptive stripping voltammetry of trace nickel

Bismuth film electrodes are shown to be very attractive alternatives to common mercury electrodes used for adsorptive stripping voltammetric measurements of trace nickel in the presence of the dimethylglyoxime complexing agent. Variables affecting the response have been assessed and optimized. Such optimization resulted in a favorable and highly stable stripping response, with good linearity (up to 80 μg L⁻¹) and precision (RSD=1.8%), and a low detection limit (0.8 μg L⁻¹ with 180 s adsorption). The adsorptive stripping performance makes the bismuth film electrode very attractive for measurements of trace metals that cannot be plated electrolytically, and should address possible restrictions on the use of mercury electrodes.     

Determination of trace amounts of dipyridamole by stripping voltammetry using a Nafion modified electrode

This paper presents a new method for determination of dipyridamole by anodic stripping voltammetry using a Nafion modified glassy carbon electrode. The stripping peak current was proportional to the concentration of dipyridamole over the range of 1.0 x 10(-9)-8.0 x 10(-8) M in (pH 1.7) BrittondashRobinson buffer with 1 min accumulation. The detection limit has been estimated as 8.0 x 10(-11) M with 4 min accumulation. The method has been successfully applied to the determination of dipyridamole in human serum.     

Determinationation of kanamycin by square-wave cathodic adsorptive stripping voltammetry

A square-wave cathodic adsorptive stripping voltametric (SWCASV) method for the determination of kanamycin was developed on a thin-film mercury electrode (TFME). The optimal working conditions for the application of the method were found to be pH 8.0, provided by a Britton-Robinson (B.R.) buffer, and an adsorption potential of +0.30 V during 300 s. The equilibration time was applied during 10 s, and potential scans were performed at a scan rate of 40 mV/s, with a square-wave frequency of 100 Hz. The measuring-system response was linear over the kanamycin concentration range from 1.2 × 10⁻⁹ to 5.0 × 10⁻⁸ M and the detection limit achieved was 4.8 × 10⁻¹⁰ M. The relative error and relative standard deviation obtained were 1.20 and 4.67%, respectively. The voltammetric procedure was applied successfully to give a rapid and precise assay of kanamycin in kanamycin sulfate injection form. Published in Elektrokhimiya in Russian, 2008, Vol. 44, No. 12, pp. 1433–1437. The text was submitted by author in English