Square wave adsorptive stripping voltammetric determination of famotidine in urine

Electrochemical studies of famotidine were carried out using voltammetric techniques: cyclic voltammetry, linear sweep and square wave adsorptive stripping voltammetry. The dependence of the current on pH, buffer concentration, nature of the buffer, and scan rate was investigated. The best results for the determination of famotidine were obtained in MOPS buffer solution at pH 6.7. This electroanalytical procedure enabled to determine famotidine in the concentration range 1 × 10⁻⁹–4 × 10⁻⁸ mol L⁻¹ by linear sweep adsorptive stripping voltammetry (LS AdSV) and 5 × 10⁻¹⁰–6 × 10⁻⁸ mol L⁻¹ by square wave adsorptive stripping voltammetry (SW AdSV). Repeatability, precision and accuracy of the developed methods were checked. The detection and quantification limits were found to be 1.8 × 10⁻¹⁰ and 6.2 × 10⁻¹⁰ mol L⁻¹ for LS AdSV and 4.9 × 10⁻¹¹ and 1.6 × 10⁻¹⁰ mol L⁻¹ for SW AdSV, respectively. The method was applied for the determination of famotidine in urine.     

吸附转移溶出伏安法测定氟罗沙星注射液含量

氟罗沙星 (ｆｌｅｒｏｘａｃｉｎ ,ＦＬＲＸ)是一种抗菌谱广 ,杀菌力强的三氟喹诺酮类抗菌药[1] 。ＦＬＲＸ含量的测定方式主要有ＨＰＬＣ法[2 ,3] 、紫外分光光度法[3,4 ] 和荧光分光光度法[5] 。本文研究ＦＬＲＸ在不同支持电解质中的电化学行为 ,发现其在石墨电极表面有很强的吸附性 ,在一定的电位下富集几分钟 ,电极冲洗后在底液中扫描 ,仍有很大的峰电流。在此基础上建立了吸附转移溶出伏安法(ＡｄＴＳＶ) [6 ] 测定ＦＬＲＸ。方法的线性范围为 4～42 μｇ/ｍｌ,用于ＦＬＲＸ葡萄糖注射液中ＦＬＲＸ含量的测定 ,比其他方法灵敏、准确、…     

Adsorptive stripping voltammetric determination of dimenhydrinate at a hanging mercury drop electrode

Dimenhydrinate exhibits a single adsorptive stripping peak at a hanging mercury drop electrode after accumulation at 0.0V vs Ag/AgCl electrode at pH 3.8 (acetate buffer). The addition of trace amounts of copper ions enhanced the dimenhydrinate peak and its height depends on the concentration of each dimenhydrinate and Cu²⁺. The adsorptive stripping response was evaluated with respect to accumulation time and potential, concentration dependence, electrolyte, the presence of other purines, surfactants and other metal ions, and some variables. The calibration graph for dimenhydrinate determination is linear over the range 2.0×10^–8–2.0×10^–7 M (pre-concentration for 60s). The correlation factor is found to be 0.985 and RSD is 3.2% at 1.0×10^–7 M. Detection limit is 1.0×10^–8 M after 5 min accumulation. The determination of dimenhydrinate in pharmaceutical formulations by the proposed method is also reported.     

Adsorptive stripping voltammetric determination of cobalt in the presence of dimethylglyoxime and cetyltrimethylammonium bromide

A sensitive procedure for determination of micro-traces of Co(II) by adsorptive stripping voltammetry is proposed. The procedure exploits the enhancement of the cobalt peak obtained by use of the system Co(II)–dimethylglyoxime–piperazine-1,4-bis(2-ethanesulfonic acid)–cetyltrimethylammonium bromide. Using the optimized conditions, a detection limit (based on the 3 criterion) for Co(II) of 1.2×10^–11 mol L^–1 (0.7 ng L^–1) was achieved. The calibration plot for an accumulation time of 30 s was linear from 5×10^–11 to 4×10^–9 mol L^–1. The procedure was validated by analysis of certified reference materials and natural water samples.     

Adsorptive stripping voltammetry of selected cephalosporin antibiotics and their direct determination in urine

Accumulation of selected cephalosporin antibiotics cefazolin, cefotaxime, cefuroxime and ceftriaxone on hanging mercury drop electrode was studied. The effects of supporting electrolyte composition, pH, accumulation potential and time were examined and corresponding analytical parameters were established employing linear sweep (staircase) or differential pulse voltammetric detection. Britton-Robinson buffer of pH 4.0 for ceftriaxone and acetate buffer in the pH range 3.6–5.0 for the other three compounds were found to be the best media. Calibration curves were linear from micromolar down to nanomolar range with limits of detection 2 × 10^–9 moll^–1, 1 × 10^–9 moll^–1, 5 × 10^–10 moll^–1 and 5 × 10^–9 moll^–1 for cefazolin, cefotaxime, cefuroxime and ceftriaxone respectively, applying the accumulation times of 5 to 14 min. Direct and simple determination of cefazolin as a model compound in urine was established with no other manipulation of urine sample than dilution 1 + 500 with buffer and subsequent adsorptive stripping voltammetric determination. The detection limit of the method is 7 gml^–1 (1.5 × 10^–5 moll^–1) of cefazolin in urine, and the relative standard deviation of 9 measurements was found to be 2.8% at 23 gml^–1 of cefazolin in urine. Similar values were found for other three compounds as well. These values are comparable or even better than those obtained by high performance liquid Chromatographic methods and approve the suitability of the proposed method for urine level monitoring in clinical practice and pharmacological studies.     

Adsorptive stripping voltammetric determination of the anti-inflammatory drug tolmetin in bulk form, pharmaceutical formulation and human serum

The electro-reduction of tolmetin at the hanging mercury drop electrode was studied in different supporting electrolytes using cyclic voltammetry and square-wave stripping voltammetry techniques. Voltammograms of tolmetin exhibited a single well-defined 2-electron irreversible cathodic peak in media of pH < 4, which may be attributed to reduction of the >C=O double bond of the analyte molecule. Adsorption of tolmetin onto the surface of the hanging mercury electrode was identified and each adsorbed tolmetin molecule was found to occupy an area of 0.23 nm². A square-wave adsorptive cathodic stripping voltammetric procedure was described for the direct determination of tolmetin in bulk form and pharmaceutical formulation (Rumatol® capsules) with a limit of quantitation of 2 × 10^?9 M and a mean percentage recovery of 98.35 ± 1.21% to 99.57 ± 1.23. Moreover, the described procedure was successfully applied for the direct assay of tolmetin in spiked human serum without pretreatment or extraction prior to the analysis while a quantitation limit of 5 × 10^?9 M tolmetin was achieved.      

Square-wave adsorptive stripping voltammetric determination of an antihistamine drug astemizole

The square-wave voltammetric technique was used to explore the adsorption properties of the astemizole drug. The analytical methodology used was based on the adsorptive preconcentration of the drug on a hanging mercury drop electrode (HMDE), followed by the electrochemical reduction process which yielded a well-defined cathodic peak at −1.184 V (vs. the Ag/AgCl electrode). To achieve high sensitivity, various experimental and instrumental variables were investigated such as the supporting electrolyte, pH, accumulation time and potential, drug concentration, scan rate, SW frequency, pulse amplitude, convection rate, and the working electrode area. Under the optimized conditions, the AdSV peak current was proportional over the analyte concentration range of 5 × 10⁻⁷ to 2.5 × 10⁻⁶ mol L⁻¹ (r = 0.998) with the detection limit of 1.4 × 10⁻⁸ mol L⁻¹ (6.4 ng mL⁻¹). The precision of the proposed method in terms of RSD was 2.4 %, whereas the method accuracy was indicated by the mean recovery of 100.1 %. Possible interferences of several substances usually present in the pharmaceutical tablets and formulations were also evaluated. The applicability of this electroanalytic approach was illustrated by the determination of astemizole in tablets and biological fluids.     

加雷沙星的吸附伏安法测定

在0.3mol·L-1KH2PO4-Na2HPO4(pH6.40)底液中,加雷沙星(Garenoxacin,简称GRX)在汞电极上有一线性扫描还原峰,峰电位EP=-1.12V(vsAg/AgCl),该峰具有明显的吸附性;吸附粒子为GRX中性分子,测得GRX在汞电极上的饱和吸附量Гs=3.92×10-11 mol·cm-2,每个GRX分子所占电极面积为1.94nm2,GRX在汞电极上的吸附符合Langmuir吸附等温式;测得吸附系数β=1.14×106,25℃时的吸附自由能ΔGθ=-29.62kJ·mol-1,电极反应电子数n=2,不可逆体系动力学参量αna=1.04,表面电极反应速率常量ks=0.25s-1;建立了吸附溶出伏安法测定GRX的最佳条件,方法的检出限为2.0×10-8 mol·L-1.     

Sensitive adsorptive stripping voltammetric method for direct determination of trace concentration of lead in the presence of cupferron in natural water samples

This paper reports the use of an adsorptive voltammetric technique for Pb(II) determination using cupferron as a selective complexing agent. After accumulation of the complex onto a hanging mercury drop electrode, the electrode potential was scanned with differential pulse modulation and the reduction current of lead was observed at about??0.5?V. Under optimum conditions (5?×?10^?4?mol?L^?1 cupferron concentration, 0.1?mol?L^?1 acetate buffer (pH 5.5), adsorption at??50?mV for 30?s) the detection limit was 5.1?×?10^?10?mol?L^?1. The relative standard deviation of five measurements for low lead concentration was 3.1%. The accuracy of the method was tested by analysing certified reference material (SPS-WW1 Waste Water). Finally, the method was successfully applied to the determination of Pb(II) in river water samples without any pretreatments.     

Adsorptive stripping voltammetry of some trace elements in biological samples. I. Cadmium and zinc

A study of the adsorptive stripping voltammetry of cadmium and zinc is reported in which ligands containing sulphur donor atoms were examined. This type of ligand showed good adsorptive behaviour and strong metal complexation. It was found that the ligand 2,5-dimer-capto-1,3,4-thiadiazole (DMTD) was very suitable for the determination of cadmium and zinc using this technique.The method was applied to the direct determination of these metals in biological samples using benzyl trimethylammonium methoxide as digesting solvent for the samples.     

Electrochemical reduction of cefminox at the mercury electrode and its voltammetric determination in urine

The electrochemical behaviour of cefminox in phosphate buffers solutions over pH range 2.0-9.0 using differential-pulse polarography, DC-tast polarography, cyclic voltammetry and linear sweep voltammetry (staircase) has been studied. In acidic media, a non reversible diffusion-controlled reduction involving two electrons occurs and the mechanism for the reduction was suggested. A differential-pulse polarographic method for the determination of cefminox in the concentration range 5.8×10⁻⁶-6.0×10⁻⁵ M with a detection limit of 1.76×10⁻⁶ M was proposed. Also, a method based on controlled adsorptive pre-concentration of cefminox on the hanging mercury drop electrode followed by linear sweep voltammetry, allows its determination in the concentration range 8.3×10⁻⁸-1.5×10⁻⁶ M with a detection limit of 2.47×10⁻⁸ M. These methods have been used for the direct determination of cefminox in human urine with recoveries between 98 and 103%, and precision around ±2%.     

Adsorptive stripping voltammetric determination of the anti-inflammatory drug celecoxib in pharmaceutical formulation and human serum

Celecoxib is a cyclooxygenase inhibitor, that has been recently and intensively prescribed as an anti-inflammatory drug in rheumatic osteoarthiritis. A robust, highly reliable and reproducible square-wave (SW) adsorptive cathodic stripping voltammetric procedure was developed for the determination of celecoxib in pharmaceutical formulation and human serum. The analytical procedure was based on the reduction of the CN of the pyrazole ring of the drug molecule at the mercury electrode surface in Britton-Robinson buffer of pH 7.0. The SW adsorptive cathodic stripping voltammogram of celecoxib showed a single well-defined peak at −1.54 V (vs. Ag/AgCl/KCl_s) using an accumulation potential of −0.70 V, frequency of 120 Hz, scan increment of 10 mV and pulse amplitude of 25 mV. Repeatability was examined for 1×10⁻⁸ M CXB drug solution after 30 s pre-concentration and a mean recovery of 99.4±0.4% (n=5) was achieved. For 90 s preconcentration, a linear concentration range of 1×10⁻⁹-2×10⁻⁸ M CXB and a detection limit of 1.86×10⁻¹⁰ M were achieved. The proposed procedure was successfully applied for the determination of the drug in capsules and human serum with mean recoveries of 101.5±0.6 and 98.8±1.1%, respectively. A detection and quantitation limits of 1.0×10⁻⁹ M (0.4 ng ml⁻¹) and 4.7×10⁻⁹ M (1.3 ng ml⁻¹) were achieved for the determination of the drug in human serum. Moreover, the procedure was useful for study of the pharmacokinetic profile of celecoxib in a healthy volunteer after administration of a single oral dose (celebrex®, 200 mg).     

白藜芦醇在银电极上的吸附伏安行为及其应用

白藜芦醇(3,5,4-三羟基芪)通常存在于葡萄、桑椹等多种植物中, 葡萄酒中也有一定的含量[1]. 由于白藜芦醇对防治癌症、动脉硬化和冠心病等疾病有较好的疗效[1,2], 近年来对白藜芦醇生物活性的研究日益受到重视. 白藜芦醇的测定一般采用高效液相色谱和毛细管电泳等方法[3～5], 这些方法均需对样品进行减压浓缩和萃取等处理, 比较繁琐. 本文对白藜芦醇在银电极上的吸附伏安行为进行了研究, 并将其应用于葡萄酒中白藜芦醇含量的直接测定, 获得了较好的实验结果.     

Simple and fast voltammetric procedure of U(VI) determination in the presence of high concentrations of surface active substances

In this work, a simple and fast procedure for elimination of interfering surface active substances and for U(VI) adsorptive stripping voltammetric determination was developed. The adsorption in the form of U(VI)-cupferron complexes was performed, because as it was proved before, U(VI) forms with cupferron stable complexes, which were employed in voltammetric procedures. The procedure is based on two steps: the first is an adsorption of surface active substances onto an Amberlite XAD-16 or XAD-7 resin and the second is a voltammetric determination of U(VI) with a pulsed potential of accumulation alternate –0.65–0.3 V with the frequency of 0.5 Hz and then the differential pulse voltammogram was recorded, whereas the potential was scanned from –0.65 to –1.2 V. The detection limit estimated from three times the standard deviation for a low U(VI) concentrations was equal to 1.7 × 10^?10 mol L^?1 (7.2 × 10^?8 g L^?1). The linear range of U(VI) was observed over the concentration range from 5.0 × 10^?10 mol L^?1 (2.1 × 10^?7 g L^?1) to 2.0 × 10^?8 mol L^?1 (8.5 × 10^?6 g L^?1) for an accumulation time of 60 s. The influence of different kinds of surfactants, such as non-ionic, cationic and anionic on the uranium voltammetric signal was studied. The results confirm the possibility of U(VI) determination in water samples containing high concentrations of surface active substances even up to 50 mg L^?1.     

碳糊电极吸附溶出伏安法测定游离钙

基于Ca(Ⅱ)-茜素红S(ARS)络合物在碳糊电极上的还原波,建立了吸附溶出伏安测定游离钙的新方法。在1.5×10-2mol/LKOH-2.0×10-5mol/LARS介质中,Ca(Ⅱ)-ARS络合物在碳糊电极上于-0.89V处产生一吸附还原波。当富集电位为.0.1V,富集时间90s,扫描速度为100mV/s时,该络合物单扫描阴极溶出峰的二阶导数峰电流与游离钙离子浓度在3.0×10-8~2.0×10-6mol/L范围内呈线性关系;检出限为9.4×10-9mol/L。在0.2mol/LHCl中清洗2min,该电极重现性良好。该方法可用于血清、牛奶和自来水中游离钙的测定。     

Catalytic adsorptive stripping voltammetric determination of copper(II) on a carbon paste electrode

A catalytic adsorptive stripping voltammetric method for the determination of copper(II) on a carbon paste electrode (PCE) in an alizarin red S (ARS)-K₂S₂O₈ system is proposed. In this method, copper(II) is effectively enriched by both the formation and adsorption of a copper(II)-ARS complex on the PCE, and is determined by catalytic stripping voltammetry. The catalytic enhancement of the cathodic stripping current of the Cu(II) in the complex results from a redox cycle consisting of electrochemical reduction of Cu(II) ion in the complex and subsequent chemical oxidation of the Cu(II) reduction product by persulfate, which reduces the contamination of the working electrode from Cu deposition and also improves analytical sensitivity. In Britton-Robinson buffer (pH 4.56±0.1) containing 3.6×10⁻⁵ mol L⁻¹ ARS and 1.6×10⁻³ mol L⁻¹ K₂S₂O₈, with 180 s of accumulation at −0.2 V, the second-order derivative peak current of the catalytic stripping wave was proportional to the copper(II) concentration in the range of 8.0×10⁻¹⁰ to ∼3.0×10⁻⁸ mol L⁻¹. The detection limit was 1.6×10⁻¹⁰ mol L⁻¹. The proposed method was evaluated by analyzing copper in water and soil.     

The catalytic adsorptive stripping voltammetric determination of chromium with TTHA and nitrate

A sensitive voltammetric method is presented for the determination of trace amounts of total chromium (Cr(III) and Cr(VI)) in natural waters, employing the square wave mode. The method is based on the preconcentration of the Cr(III)-TTHA complex by adsorption at the HMDE at the potential of –1.0 V vs. Ag/AgCl. The adsorbed complex is then reduced producing a response with a peak potential of –1.29 V and the peak height of the Cr(III) reduction is measured. The catalytic action of the nitrate ions on the Cr(III)-TTHA reduction has been elucidated using cyclic voltammetry. The adsorption of chromium complexes at the HMDE was investigated using out-of-phase a.c. voltammetry and the potential range of adsorption was determined.Based on these investigations optimal conditions for the determination of the total chromium concentration in the range 155–2000 ng 1^–1 have been established. The determination limit is 15 ng 1^–1 and the RSD is 3.5% for chromium concentrations 200 ng 1^–1.The usefulness and wide scope of this method for reliable and highly sensitive chromium analysis down to the ultra trace levels existing in various types of natural waters is demonstrated by determinations of the total chromium content in lake, sea and rain water.     

Application of artificial neural networks to the determination of pesticides by linear sweep stripping voltammetry

In this work, artificial neural network (ANN), a powerful chemometrics approach for linear and nonlinear calibration models, was applied to detect three pesticides in mixtures by linear sweep stripping voltammetry (LSSV) despite their overlapped voltammograms. Electrochemical parameters for the voltammetry, such as scan rate, deposit time and deposit potential, were evaluated and optimized from the signal response data using ANN model by minimizing the relative prediction error (RPE). The proposed method was successfully applied to the detection of pesticides in synthetic samples and several commercial fruit samples.     

Adsorptive Stripping Voltammetry of Phytohemagglutinin

Abstract

The adsorptive stripping voltammetric behaviour of the lectin, phytohemagglutinin, has been optimised with respect to accumulation time, accumulation potential, pulse amplitude, scan rate and drop size. Adsorptive stripping voltammetry has also been used to study the interaction of this protein with nannose, galactose and N-acetyl-D-galactosamine.     

Cathodic and Adsorptive Stripping Votammetry of Naftazone

Abstract

Naftazone (1,2-naphthoquinone-2-semicarbazone) undergoes a reversible two-electron transfer in both acidic and alkaline solutions and also gives rise at pH > 7 to an anodic wave attributed to the formation of a mercury derivative. Cathodic stripping voltammetry is proposed to determine the compound down to 5 × 10^?9 M after accumulation of its mercury salt formed at -0.05V in a 0.05M sodium hydroxide solution. These results have been compared with those obtained by performing an adsorptive collection of the drug in a pH 3 sodium perchlorate solution. Concentrations ranging from 1 × 10^?7 to 2 × 10^?7M can be easily investigated, the detection limit being 7 × 10^?11M. The influence of several operational parameters has also been considered.