Adsorptive Stripping Differential Pulse Voltammetry for Determination of Trace Amounts of Noscapine in Human Plasma

A new adsorptive anodic differential pulse stripping voltammetry method for the direct determination of noscapine at trace levels in human plasma of addicts is proposed. The procedure involves an adsorptive accumulation of noscapine on a hanging mercury drop electrode (HMDE), followed by oxidation of adsorbed noscapine by voltammetry scan using differential pulse modulation. The optimum conditions for the analysis of noscapine are pH = 8.5 using Britton‐Robinson (B‐R) buffer, accumulation potential of ?100 mV (vs. Ag/AgCl), and accumulation time of 150 s. The peak current is proportional to the concentration of noscapine, and a linear calibration graph is obtained at 0.015–2.75 μg mL^?1. A relative standard deviation of 1.28% (n = 5) was obtained, and the limit of detection was 7 ng mL^?1. The capability of the method for the analysis of real samples was evaluated by determination of noscapine in spiked human plasma and addicts, human plasma with satisfactory results.     

Simultaneous voltammetric determination of morphine and noscapine by adsorptive differential pulse stripping method and least-squares support vector machines

An adsorptive differential pulse stripping method for the simultaneous determination of morphine and noscapine is proposed. The procedure involves an adsorptive accumulation of morphine and noscapine on a hanging mercury drop electrode (HMDE), followed by oxidation of adsorbed morphine and noscapine by voltammetric scan using differential pulse modulation. The optimum experimental conditions are: pH 10.0, accumulation potential of −100 mV versus Ag/AgCl, accumulation time of 150 s, scan rate of 40 mV s⁻¹ and pulse height of 100 mV. Morphine and noscapine peak currents were observed in same potential region at about +0.25 V. The simultaneous determination of morphine and noscapine by using voltammetry is a difficult problem in analytical chemistry, due to voltammogram interferences. The resolution of mixture of morphine and noscapine by the application of least-squares support vector machines (LS-SVM) was performed. The linear dynamic ranges were 0.01-3.10 and 0.015-2.75 μg mL⁻¹ and detection limits were 3 and 7 ng mL⁻¹ for morphine and noscapine, respectively. The capability of the method for the analysis of real samples was evaluated by the determination of morphine and noscapine in addict's human plasma with satisfactory results.     

Determination of Trace Amounts of Lorazepam by Adsorptive Cathodic Differential Pulse Stripping Method in Pharmaceutical Formulations and Biological Fluids

Abstract

A new adsorptive cathodic differential pulse stripping voltammetry method for the direct determination of lorazepam at trace levels in pharmaceutical formulations and biological fluids is proposed. The procedure involves an adsorptive accumulation of lorazepam on a hanging mercury drop electrode (HMDE), followed by reduction of adsorbed lorazepam by voltammetric scan using differential pulse modulation. The optimum conditions for the analysis of lorazepam are pH=2 using Britton‐Robinson (B‐R) buffer, accumulation potential of ?0.2 V (vs. Ag/AgCl), and accumulation time of 40 sec. The peak current is proportional to the concentration of lorazepam, and a linear calibration graph is obtained at 0.05–1.15 µg mL^?1. A relative standard deviation of 2.41% (n=3) was obtained, and the limit of detection was 0.019 µg mL^?1. The capability of the method for the analysis of real samples was evaluated by determination of lorazepam in pharmaceutical preparations and biological (urine and plasma) fluids with satisfactory results.     

Determination of Salbutamol in Pharmaceutical and Serum Samples by Adsorptive Stripping Voltammetry on a Carbon Paste Electrode Modified by Iron Titanate Nanopowders

This study introduces a fast and direct electrochemical method for the determination of salbutamol using an iron titanate nanopowder‐modified carbon paste electrode. The electrochemical behavior of salbutamol was studied by differential pulse adsorptive stripping voltammetry. Factors affecting the performance of the adsorptive stripping such as the modifier percent, the electrolyte pH and accumulation time and potential were optimized. The resulting electrode exhibited a linear response in the range of 0.2–25 nM of salbutamol with a detection limit of 90 pM. The proposed method was successfully applied to determine salbutamol in pharmaceutical formulations and human blood plasma.     

A reliable and ultrasensitive voltammetric method for the determination of molybdenum

Summary The determination of molybdenum(VI) in aquatic media by polarography, voltammetry and adsorptive stripping voltammetry using the formation of a Mo-chlorate-mandalic acid complex at +100 mV (SCE) is described. The 3 s_blank-detection limit is 0.1 nmol/l with differential pulse adsorptive stripping voltammetry (DPAdsSV, catalytic current). The calibration graphs are linear up to 200 nmol/l for the latter, 400 nmol/l for staircase voltammetry without accumulation time and 1 mg/l for staircase polarography. The accuracy of the DPAdsSV method was checked by analysis of a standard reference water material. The utility of differential pulse voltammetry was tested in different aquatic media, e.g., tap water, ground water, surface water.

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Eine zuverlässige und äußerst empfindliche Methode zur Bestimmung von Molybdän

     

Polydopamine-modified MWCNTs-glassy Carbon Electrode,a Selective Electrochemical Morphine Sensor

An electrochemical sensor based on a glassy carbon electrode was prepared using f-MWCNTs and polydopamine. Several techniques were used to investigate the surface features. Voltammetric techniques were used to evaluate the electrocatalyst efficiency, and it was used for morphine determination using differential pulse voltammetry. Different parameters affecting the method‘s sensitivity and selectivity were optimized. The linear dynamic range was 0.075–75.0 μM with a detection limit of 0.06 μM morphine. Also, the method‘s selectivity was tested, which was proved to be satisfactory. Finally, the sensor was successfully used for morphine determination in human plasma and urine samples with acceptable results.     

Voltammetric studies of a psychotropic drug with nitro groups. Determination of flunitrazepam in urine using HMDE

The adsorption behaviour of flunitrazepam at the hanging mercury drop electrode was studied by staircase voltammetry and by adsorptive stripping differential pulse voltammetry. Flunitrazepam is adsorbed in the whole potential range, from the most positive values up to the reduction potential. Flunitrazepam reduction product is also adsorbed. The time dependence of the voltammetric response proves that a diffusion-controlled adsorption takes place. Flunitrazepam can be determined (down to nanomolar levels) by using adsorptive preconcentration prior to the differential pulse voltammetric scan. An application of such a method to flunitrazepam determination in human urine is described. The detection limit was 30 ng per milliliter of urine with a 20-sec accumulation time; the mean relative standard deviation was lower than 3.2% and the mean recovery 97.8%.     

Trace amounts determination of lead,zinc and copper by adsorptive stripping voltammetry in the presence of dopamine

A selective and sensitive method for simultaneous determination of lead, zinc and copper by adsorptive differential pulse cathodic stripping voltammetry is presented. The method is based on adsorptive accumulation of the complexes of Pb(II), Zn(II), and Cu(II) ions with dopamine onto hanging mercury drop electrode (HMDE), followed by reduction of adsorbed species by differential pulse cathodic stripping voltammetry. The effect of experimental parameters such as pH, dopamine concentration, accumulation time and potential and scan rate were examined. Under the optimized conditions, linear calibration curves were established for the concentration of Pb, Zn, and Cu in the ranges of 5–150, 5–250, and 1–150 ng/mL, respectively. Detection limits of 0.06, 0.25, and 0.04 ng/mL for Pb, Zn, and Cu were obtained. An application of the proposed method is reported for the determination of these elements in some real samples such as natural waters and alloys.     

Cathodic adsorptive stripping square-wave voltammetry of the anti-inflammatory drug meloxicam

The adsorptive behavior of the anti-inflammatory drug meloxicam was studied by cyclic, differentia-pulse and square-wave voltammetry on a hanging mercury drop electrode (HMDE). The drug was accumulated at HMDE and a well-defined stripping peak current was obtained at -1.42 V vs. Ag/AgCl (saturated KCl) electrode in acetate buffer solution (pH 5.0). A voltammetric procedure was developed for the determination of meloxicam using square-wave cathodic adsorptive stripping voltammetry (SW-CASV). The optimum working conditions for the determination of the drug were established. The analysis of meloxicam in human plasma was carried out satisfactorily.     

Simultaneous Differential Pulse Adsorptive Stripping Determination of Imipramine and Its Metabolite Desipramine by the PLS‐1 Multivariate Method

A method, using stripping differential pulse voltammetry, for the simultaneous determination of Imipramine and its metabolite Desipramine is reported. Both compounds produce, at glassy carbon electrode, an electrochemical signal due to an adsorptive‐oxidative process. The voltammograms show a very high overlap degree between IM and DE peaks. The multivariate calibration method PLS‐1 was employed for the simultaneous determination of both compounds. An experimental design together with the response surface methodology has been used to find the optimum experimental conditions. The developed procedure has been utilized in the analysis of fortified human serum samples with good recovery values for each analyte.     

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 Cobalt Ions in Natural Waters Using Differential Pulse Adsorptive Stripping Voltammetry

Abstract

Differential pulse adsorptive stripping voltammetry using dimethylglyoxime complexes in the presence of triethanolamine and ammonium chloride can be applied to the determination of cobalt (II) ions in natural waters with high sensitivity. The limit of detection is about 3 ppt. Actual analysis of estuary water are reported. In this particular case of natural water, the factors influencing the use of differential pulse adsorptive stripping voltammetry for the determination of cobalt are described in detail.     

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     

Simultaneous determination of Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe in water samples by differential pulse stripping voltammetry at a hanging mercury drop electrode

A highly sensitive and selective voltammetric procedure is described for the simultaneous determination of eleven elements (Cd, Pb, Cu, Sb, Bi, Se, Zn, Mn, Ni, Co and Fe) in water samples. Firstly, differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) is used for the direct simultaneous determination of Cd, Pb, Cu, Sb and Bi in 0.1 M HCI solution (pH = 1) containing 2 M NaCl. Then, differential pulse cathodic stripping voltammetry (DPCSV) is used for the determination of Se in the same solution. Zn is subsequently determined by DPASV after raising the pH of the same solution to pH 4. Next, the pH of the medium is raised to pH 8.5 by adding NH3/NH4Cl buffer solution for the determination of Mn by DPASV. Ni and Co are determined in the same solution by differential pulse adsorptive stripping voltammetry (DPAdSV) after adding DMG (1 x 10(-4) M). Finally, 1 x 10(-5) M 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) is added to the solution for the determination of Fe by DPAdSV. The optimal conditions are described. Relative standard deviations and relative errors are calculated for the eleven elements at three different concentration levels. The lower detection limits for the investigated elements range from 1.11 x 10(-10) to 1.05 x 10(-9)M, depending on the element determined. The proposed analysis scheme was applied for the determination of these eleven elements in some ground water samples.     

Voltammetric Determination of Selected Aminoquinolines Using Carbon Paste Electrode

Optimum conditions have been found for voltammetric determination of mutagenic 5‐aminoquinoline, 6‐aminoquinoline and 3‐aminoquinoline by differential pulse voltammetry and adsorptive stripping differential pulse voltammetry on carbon paste electrode. The lowest limits of determination were found for adsorptive stripping differential pulse voltammetry in 0.1 mol dm^?3 H₃PO₄ (5×10^?7 mol dm^?3 , 1×10^?7 mol dm^?3, and 1×10^?7 mol dm^?3 for 5‐aminoquinoline, 6‐aminoquinoline and 3‐aminoquinoline, respectively). The possibility to determine mixtures of 8‐aminoquinoline with 3‐aminoquinoline or 5‐aminoquinoline or 6‐aminoquinoline, and mixtures of 5‐aminoquinoline with 3‐aminoquinoline or 6‐aminoquinoline by differential pulse voltammetry was verified. Binary mixtures of 8‐aminoquinoline with 3‐aminoquinoline or 6‐aminoquinoline, and of 3‐aminoquinoline with 5‐aminoquinoline could be successfully analyzed.     

Catalytic adsorptive stripping voltammetry determination of ultra trace amount of tungsten using factorial design for optimization

A highly sensitive procedure is presented for the determination of ultra-trace concentration of tungsten by catalytic adsorptive stripping voltammetry. The method is based on adsorptive accumulation of the tungsten-pyrocatechol violet complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by chlorate. The influence of variables was completely studied by factorial design analysis. Optimum analytical conditions for the determination of tungsten were established. Tungsten can be determined in the range 0.06–12.0 ng/mL with a limit of detection of 0.02 ng/mL. The influence of potentially interfering ions on the determination of tungsten was studied. The procedure was applied to the determination of tungsten in one sandwich polyoxometalate and some synthetic samples similar to alloy compounds with satisfactory results.     

Electrochemical behavior and determination of clozapine on a glassy carbon electrode modified by electrochemical oxidation.

The adsorptive and electrochemical behaviors of clozapine (CLZ) were investigated on a glassy carbon electrode that was electrochemically treated by anodic oxidation at +1.8 V, following potential cycling in the potential range from -0.8 to 1.0 V vs. Ag/AgCl reference electrode. Based on the obtained electrochemical results, an electrochemical-chemical (EC) mechanism was proposed to explain the electrochemical oxidation of CLZ. The resulting electrochemically pretreated glassy carbon electrode (EPGCE) showed good activity to improve the electrochemical response of the drug. CLZ was accumulated in a phosphate buffer (pH 6) at a certain time, and then determined by differential pulse voltammetry. The anodic and cathodic peak currents showed a linear function in the concentration ranges of 0.1 - 1, 1 - 10 and 10 - 100 microM with various accumulation times. The proposed method was successfully used for the determination of CLZ in pharmaceutical preparations. The preconcentration medium-exchange approach was utilized for the selective determination of the drug in spiked urine samples with satisfactory results. The recovery levels of the method reached 96% (RSD, 1.8%) and 90% (RSD, 2.8%) for urine and plasma samples, respectively.     

Electrochemical behavior and voltammetric determination of the herbicide metribuzin at mercury electrodes

The electrochemical behavior of the herbicide metribuzin (4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one) at mercury electrodes was studied in aqueous solutions by direct current (DC) and tast polarography, differential pulse (DPV) and cyclic voltammetry (CV), and controlled-potential coulometry. The electrolysis products were separated and identified by chromatographic techniques combined with mass spectrometric detection. The reduction process in acid media includes two irreversible steps. In the first four-electron step the N-NH2 and the 1,6-azomethine bonds are reduced. The second step leads to the formation of 5-tert-butyl-2,3,4,5-tetrahydroimidazol-4-one at the mercury-pool electrode. The first reduction step combined with adsorptive accumulation of the herbicide molecule at the mercury electrode surface was used for its determination by differential pulse adsorptive stripping voltammetry (DPAdSV). Calibration curves were linear in the range 1-30 microg L(-1) with a detection limit of 0.27 microg L(-1) (1 nmol L(-1)) under the conditions used (buffer pH 4.5, Eacc = -0.45 V relative to Ag/AgCl and tacc = 10 s). Preconcentration on solid-phase extraction columns (SPE-phenyl) was used for the determination of very small amounts of metribuzin in river water samples. Recovery was approximately 97%. The reproducibility of the analytical procedure including SPE treatment and DPV determination was expressed as relative standard deviations of 2.53 and 3.66% for 2 and 6 microg L(-1) metribuzin, respectively.     

Study of the electrochemical behaviour of metaclazepam in aqueous media and its determination in biological fluids

Summary The polarographic behaviour of metaclazepam in Britton Robinson universal buffer has been investigated by the following techniques: DC tast and differential pulse polarography, cyclic voltammetry, microcoulometry and adsorptive stripping voltammetry. The compound is polarographically active over the entire pH-range, showing a single well-defined wave. This has been characterized as being a 2e^– diffusion-controlled wave in acid media. The reduction step is due to the C=N group. The drug is also surface-active and the adsorption at the electrode is higher in alkaline than in acid media. A stripping method for the determination of this psychotropic drug at the sub-micromolar and nanomolar concentration levels is described. Adsorptive accumulation for 300 s followed by differential pulse measurement in Britton Robinson buffer at pH 9.1 can be used for the determination of metaclazepam in urine with an accuracy and precision of 2% and 3%, respectively. The detection limit was 0.55 ng per ml of urine (adsorptive accumulation at –0.60 V for 300 s).     

氧化锌纳米簇-金纳米颗粒-壳聚糖复合膜修饰电极用于示差脉冲伏安法测定吗啡

将制备的氧化锌纳米簇和金纳米颗粒分散在壳聚糖中并滴涂在玻碳电极表面,制备了氧化锌纳米簇-金纳米颗粒-壳聚糖复合膜修饰电极(Au-ZnO-CHIT/GCE)。采用循环伏安法研究了吗啡在修饰电极上的电化学行为。结果表明:吗啡在该修饰电极上出现了一个氧化峰,提出了用示差脉冲伏安法测定吗啡的方法。吗啡浓度在5.3×10-6~6.5×10-4mol.L-1范围内与氧化峰电流呈线性关系,检出限(3S/N)为1.8×10-6mol.L-1。修饰电极用于尿液中吗啡的测定,回收率在80.0%~99.6%之间。