Adsorptive stripping voltammetric assay of phenazopyridine hydrochloride in biological fluids and pharmaceutical preparations

A sensitive method for the measurement of phenazopyridine hydrochloride (PAP) by differential pulse polarography (DPP) based on adsorptive stripping technique, using a hanging mercury drop electrode (HMDE) is described. The voltammetric peak is obtained at -0.760 V, which corresponds to the reduction of the azo group in Britton-Robinson buffer. The redox behaviour is reversible. Optimum conditions were found to be: accumulation potential -50 mV (vs. Ag/AgCl), accumulation time 60 s, scan rate 5 mV s(-1), pulse amplitude -100 mV and supporting electrolyte Britton-Robinson buffer (0.04 M, pH=11). The relative standard deviation (at 20 ng ml(-1) level) was +/-0.6% for six measurements. The calculated detection limit was 0.0299 ng ml(-1) with a 60-s accumulation time. The applicability of such a method was evaluated through the assay of PAP in human plasma and urine samples after a simple extraction procedure and in pharmaceutical preparation. The mean recovery was 97+/-2 (100 ng ml(-1) plasma).     

Differential pulse adsorption stripping voltammetric determination of copper(II) with 2-mercaptobenzimidazol at a hanging mercury-drop electrode.

Copper(II) was selectively accumulated on a hanging mercury-drop electrode by using 2-mercaptobenzimidazole. Ensuing measurements were carried out by differential pulse adsorption stripping voltammetry. Factors affecting the accumulation, reduction, and stripping steps were investigated and a procedure was developed. The optimum conditions for the analysis of copper were pH 5.0, 5.33 x 10(-5) M 2-mercaptobenzimidazole and an accumulation potential of -0.10 V (vs. Av/AgCl). A linear range was obtained in the concentration range 0.2-100 ng/ml with a 90 s accumulation time and a scan rate of 16 mV/s. For ten successive determinations of 1.0, 20.0 and 70.0 ng/ml copper(II), relative standard deviations of 4.2, 3.5 and 2.8%, respectively, were obtained. The developed method was applied to the determination of copper in commercial salts and aluminium alloys.     

Adsorptive voltammetric determination of copper with a benzoin oxime graphite paste electrode

A method for the determination of trace amounts of copper with a chemically modified carbon press-formed electrode is described. Copper could be accumulated at the electrode by complexing with benzoin oxime in ammonia buffer, then reduced at a constant potential of −0.4 V (vs. SCE) in nitric acid solution. Finally, a well-defined stripping peak could be obtained by scanning the potential in a positive direction. The response depends on the concentration of copper and accumulation time. For an accumulation time of 5 min the detection limit is about 1 ng/ml and the linear range is from 2 ng/ml to 4000 ng/ml, with a relative standard deviation of 5%. Many common metal ions have little or no effect on the determination of copper. The recommended procedure was applied to the determination of trace amounts of copper in natural water, and the results are in agreement with those of atomic-absorption spectrometry.     

Simultaneous voltammetric determination of molybdenum and copper by adsorption cathodic differential pulse stripping method using a principal component artificial neural network

An adsorption differential pulse stripping method for the simultaneous determination of molybdenum and copper based on the formation of their complexes with cupferron (benzene, N-hydroxy-N-nitroso) is proposed. The optimum experimental conditions were obtained 0.010 mM cupferron, pH 3.0, accumulation potential of -0.15 V versus Ag/AgCl, accumulation time of 60 s, scan rate of 10 mV s(-1) and pulse height of 50 mV. Molybdenum and copper peak currents were observed at -0.16 and +0.02 V, respectively. A principal component artificial neural network (PC-ANN) was utilized for the analysis of the voltammogram data. A three layer back-propagation network was used with sigmoidal transfer function for the hidden and the output layers. The linear dynamic ranges were 5.0-60.0 and 0.1-20.0 ng ml(-1) for Cu(II) and Mo(VI), respectively. The detection limit was 0.06 ng ml(-1) for Mo(VI) and 0.20 ng ml(-1) for Cu(II). The capability of the method for the analysis of real samples was evaluated by the determination of molybdenum and copper in river water, tap water, and alloy.     

Selective determination of trace copper(II) by cathodic adsorptive stripping voltammetry with a naphthol-derivative Schiff's base

A selective and sensitive stripping voltammetric method for the determination of trace amounts of copper(II) with a recently synthesized naphthol-derivative Schiff's base (2,2'-[1,2-ethanediylbis(nitriloethylidyne)]bis(1-naphthalene)) is presented. The method is based on adsorptive accumulation of the resulting copper-Schiff's base complex on a hanging mercury drop electrode, followed by the stripping voltammetric measurement at the reduction current of adsorbed complex at -0.15 V (vs. Ag/AgCl). The optimal conditions for the stripping analysis of copper include pH 5.5 to 6.5, 8 microM Schiff's base and an accumulation potential of -0.05 V (vs. Ag/AgCI). The peak current is linearly proportional to the copper concentration over a range 2.3-50.8 ng ml(-1) with a limit of detection of 1.9 ng ml(-1). The accumulation time and RSD are 90 s and (3.2-3.5)%, respectively. The method was applied to the determination of copper in some analytical grade salts, tap water, human serum and sheep's liver.     

Subnanomolar Determination of Indium by Adsorptive Stripping Differential Pulse Voltammetry Using Factorial Design for Optimization

Abstract

A highly sensitive method to determine of indium is proposed by adsorption stripping differential pulse cathodic voltammetry (AdSDPCV) method. The complex of indium ions with xylenol orange is analyzed based on the adsorption collection onto a hanging mercury drop electrode (HMDE). After accumulation of the complex at ?0.20 V vs. Ag/AgCl reference electrode, the potential is scanned in a negative direction from ?0.40 to ?0.75 V with the differential pulse method. Then, the reduction peak current of In(III)–XO complex is measured. The influence of chemical and instrumental variables was studied by factorial design analysis. Under optimum conditions and accumulation time of 60 s, linear dynamic range was 0.1–10 ng/ml (8.7 × 10^?10 to 8.7 × 10^?8 M) with a limit of detection of 0.03 ng/ml (2.6 × 10^?10 M); at accumulation time of 5 min, linear dynamic range was 0.04–10 ng/ml (3.4 × 10^?10 to 8.7 × 10^?8 M) with a limit of detection of 0.013 ng/ml (1.1 × 10^?10 M). The applicability of the method to analysis of real samples was assessed by the determination of indium in water, alloy, and jarosite (zinc ore) samples.     

Determination of palladium(II) with alpha-(2-benzimidazolyl)-alpha',alpha'-(N-5-nitro-2-pyridylhydrazone)-toluene by adsorptive cathodic stripping voltammetry

The determination of palladium(II) complexed with alpha-(2-benzimidazolyl)-alpha',alpha'-(N-5-nitro-2-pyridylhydrazone)-Toluene (BINPHT) was investigated by adsorptive cathodic stripping voltammetry using hanging mercury drop electrode. Palladium(II) in the sample solution can be determined in BINPHT and ethylenediaminetetraacetic acid (EDTA). Accumulation is achieved by adsorption of Pd(II)-BINPHT complex on a hanging mercury drop electrode. Optimal conditions were found to be: supporting electrolyte; 0.01 M sodium acetate buffer at pH 5.0, accumulation potential; -590 mV versus Ag/AgCl, accumulation time; 180 s, scan rate; 50 mV s(-1), concentration of BINPHT; 2x10(-5) M. The linear range of Pd(II) was observed over the concentration range 20-100 ng ml(-1) The detection limit (S/N=3) is 2 ng ml(-1). A good reproductivity shows RSD of 2.0% (n=7). This procedure offers high selectivity with the presence of EDTA masking some metallic ions. River water sample spiking with palladium was determined.     

Application of adsorptive stripping voltammetry to the determination of the psychoactive drug temazepam in urine

Summary The influence of various operational parameters on the stripping response for temazepam is discussed. Interfacial and redox behaviour was also studied. 205 Ų was the average surface area per adsorbed molecule.The determination of temazepam in urine can be performed by using adsorption as a preconcentration step previous to its measurement at the hanging mercury drop electrode by differential pulse voltammetry in 0.01 mol/l Britton-Robinson buffer at pH 3.0 with a –0.50 V accumulation potential. The detection limit was 17 ng temazepam per ml of urine (15 s accumulation time) and the relative standard deviation was lower than 6.0% for 500 ng ml^–1 samples (10 s). The effects of various urine components on the voltammetric response have also been studied.

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Anwendung der adsorptiven Stripping-Voltammetrie zur Bestimmung des Psychopharmakons Temazepam in Urin

     

Determination of Copper by an Adsorption Differential Pulse Stripping Method with Naphthol Derivative

ABSTRACT

A simple, sensitive and selective method is proposed for the determination of copper(II) by adsorption-differential pulse stripping method. This method is based on the selective accumulation of the complexes of Cu(II) with l-(2-pyridylazo)-2-Naphthol and then reduction of the complex on a HMDE. The reduction current of the complex is about 0.0V vs. Ag/AgCl reference electrode at p8543146=4.0. The influences of various experimental parameters on the current peak were completely studied. The calibration graph was linear up to 50.0 ng/ml for a deposition time of 60 sec. The relative standard deviation was 2.3% (n=5) for Cu(II) concentration of 10.0 ng/ml, with a limit of detection of 0.2 ng/ml. The influence of potentially interfering ions was completely studied. The method has been applied for the determination of Cu(II) in water samples.     

Application of laser-excited atomic fluorescence spectrometry to the determination of iron

A frequency-doubled, flashlamp-pumped tunable dye laser is used to excite the Stokes direct-line atomic fluorescence transition of iron (296.7 nm/373.5 nm). Limits of detection are determined with single (0.6 ng/ml) and multipass (0.2 ng/ml) and with a l s time constant (a 0.06 ng/ml limit detection is obtained with an 8 s time constant). Noise sources limiting precision at both low (background flame emission shot and flicker noise) and high concentrations (laser pulse to pulse variability) concentrations are investigated and the technique is used for the determination of iron in simulated fresh water NBS SRM-1643), unalloyed copper (NBS SRM-394) and fly ash (NBS SRM-1633).     

Determination of ketorolac in human serum by square wave adsorptive stripping voltammetry

The adsorption behavior of ketorolac on a hanging mercury drop electrode (HMDE) was explored by square-wave and cyclic voltammetry. The square wave voltammetric response of ketorolac depends on the parameters of the square wave voltammetry excitation signal as well as on the pH of the medium and the accumulation time. The drug was accumulated at HMDE and a well-defined peak was obtained at -1.41 V versus. Ag/AgCl (saturated KCl) in acetate buffer of pH 5.0. A square-wave adsorptive stripping voltammetric method for the quantitative determination of ketorolac was developed. The linear concentration range was 1x10(-10)-1x10(-8) when using 300 s accumulation at -0.8 V. The detection limit of ketorolac was 1.0x10 (-11)M . The precision was excellent with relative standard deviation of 3.85% at concentration of 5x10 (-8)M after 60 s accumulation time. Applicability to serum samples was illustrated. A detection limit of 14 ng per ml of serum was obtained.     

Determination of cobalt by catalytic-adsorptive differential pulse voltammetry in the presence of 2-aminocyclopentene-1-dithiocarboxylic acid and nitrite

A novel method for the determination of cobalt(II) by stripping voltammetry is described. It involves an adsorptive accumulation of the cobalt(II)-2-aminocyclopentene-1-dithiocarboxylic acid complex on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of the catalytic reduction current of the complex at –1.4 V at pH = 9 (vs. Ag/AgCl). The effects of various experimental parameters on the catalytic current were investigated. An accumulation time of 60 s results in a low experimental limit of detection of 0.1 ng/mL of Co(II), and 0.50 to 40.0 ng/mL of cobalt can be determined. The relative standard deviation at 0.50 ng/mL is 2.8%. Possible interferences from co-existing ions were also investigated. Received: 17 August 1998 / Revised: 16 November 1998 / Accepted: 20 November 1998     

A Disposable Carbon Nanotubes‐screen Printed Electrode (CNTs‐SPE) for Determination of the Antifungal Agent Posaconazole in Biological Samples

For the first time, the use of carbon nanotubes was exploited for the development of a sensitive electrochemical method for determination of the newly antifungal posaconazole (POS). The electrochemical activity of POS was investigated at the surface of multi‐walled nanotubes (MWNTs) modified electrode. The cyclic voltammograms showed a sharp oxidation peak at potential around 671 mV vs. Ag/AgCl. To reach the assay optimization, factors affecting the method sensitivity have been investigated, such as types of carbon nanotubes and its concentration in the electrode matrix, type of supporting electrolyte, pH, accumulation time and scan rate. A good linear relationship was obtained within the concentration range from 32–1280 ng/ml with the limit of detection and quantification of 11 ng/ml and 33 ng/ml, respectively. The proposed method was successfully applied for the determination of POS in its commercial dosage form, spiked human plasma samples, and dried blood spots. The in vivo results obtained were also used to study the pharmacokinetics of POS in human plasma. The results obtained were validated and found to be in accordance with those obtained by the reference methods.     

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 cobalt by catalytic-adsorptive differential pulse voltammetry in the presence of 2-aminocyclopentene-1-dithiocarboxylic acid and nitrite

A novel method for the determination of cobalt(II) by stripping voltammetry is described. It involves an adsorptive accumulation of the cobalt(II)-2-aminocyclopentene-1-dithiocarboxylic acid complex on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of the catalytic reduction current of the complex at –1.4 V at pH = 9 (vs. Ag/AgCl). The effects of various experimental parameters on the catalytic current were investigated. An accumulation time of 60 s results in a low experimental limit of detection of 0.1 ng/mL of Co(II), and 0.50 to 40.0 ng/mL of cobalt can be determined. The relative standard deviation at 0.50 ng/mL is 2.8%. Possible interferences from co-existing ions were also investigated. Received: 17 August 1998 / Revised: 16 November 1998 / Accepted: 20 November 1998     

High sensitive determination of trace amount of cobalt by catalytic adsorptive stripping voltammetry

A very sensitive and selective catalytic adsorptive cathodic stripping procedure for trace measurements of cobalt is presented. The method is based on adsorptive accumulation of cobalt-CCA (calcon carboxylic acid) 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 nitrite. The effect of various parameters such as pH, concentration of CCA, concentration of nitrite, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum condition for the analysis of cobalt, include pH 5.2 (Acetate buffer), 2.1 μM clacon carboxylic acid, 0.032 M sodium nitrite and an accumulation potential of 0.05 V (versus Ag/AgCl). Under these optimum conditions and for an accumulation time of 60 s, the measured peak current at −0.480 V is proportional to the concentration of cobalt over the entire concentration range tested 0.003–2.0 ng ml⁻¹ with a detection limit of 1 pg ml⁻¹ for an accumulation time of 60 s and 2.0–10.0 ng ml⁻¹ for an accumulation time of 40 s. The relative standard deviations for ten replicate measurement of 0.5 ng ml⁻¹ of cobalt were 3.1%. The main advantage of this new system is the microtrace Co(II) determination by ASV. The method was applied to determination of cobalt in a water sample and some analytical grade salts with satisfactory results. Published in Elektrokhimiya in Russian, 2009, Vol. 45, No. 2, pp. 221–228. The article is published in the original.     

Carbon-fiber microsensor for in vivo monitoring of trace zinc(II) based on electrochemical stripping analysis

The optimization and characterization of a microsensor for trace zinc based on stripping voltammetry at a single carbon-fiber microelectrode are reported. Despite the absence of a mercury coverage, the carbon-fiber stripping sensor displays a significant hydrogen overvoltage in the physiological pH and a well-defined zinc stripping peak (at ca. −1.17 V). 5 s deposition periods allow convenient quantitation of zinc over the 100–1000 ng/ml (ppb) range. Detection limits of 0.8 ng/ml (1.2×10⁻⁸ M) and 20 ng/ml (3.0×10⁻⁷ M) zinc were estimated in connection to 60 and 1 s deposition, respectively. The response is reversible with the stripping/measurement step completely removing the accumulated zinc. Measurement frequencies as high as 30 runs per min can thus be realized (in connection to 1 s deposition and measurement steps). The influence of relevant variables of the deposition and stripping steps is examined. The attractive behavior of the stripping-voltammetric microsensor offers great promise for in vivo monitoring of trace levels of zinc.     

Simultaneous determination of carbaryl and azinphos-methyl in water by first-derivative synchronous spectrofluorimetry

A method is proposed for the simultaneous determination of the pesticides carbaryl (CBL) and azinphos-methyl (AZM) in water by first-derivative synchronous spectrofluorimetry. It is based on the alkaline hydrolysis of both pesticides to their metabolites 1-naphthol (from CBL) and anthranilic acid (from AZM). The constant wavelength difference chosen to optimize the determination is Δλ=λ_em?λ_ex=103 nm. CBL is measured at 302/405 nm and AZM at 333/436 nm. The calibration graphs are linear between 2.0 and 500.0 ng/ml for CBL and between 1.2 and 500.0 ng/ml for AZM with detection limits of 0.62 ng/ml and 0.35 ng/ml, respectively. The precision of the method (RSD) is 2.4% at the 80.0 ng/ml level for CBL and 2.5% at the 80.0 ng/ml level for AZM. The method is applied to the determination of both analytes in samples of natural waters.     

Quantification of terbutaline in pharmaceutical formulation and human serum by adsorptive stripping voltammetry at a glassy carbon electrode

The electrochemical oxidative behavior of terbutaline at the glassy carbon electrode was studied in a series of the Britton-Robinson buffer of pH 2--11. Cyclic and square-wave voltammograms of terbutaline at the pH values 相似文献   

Measurement of nanomolar levels of psychoactive drugs in urine by adsorptive stripping voltammetry

Adsorptive stripping voltammetry was used to determine nanomolar levels of the benzodiazepines pinazepam, camazepam, bromazepam and thienodiazepine (BrTDO) in urine. Measurements were made by differential pulse voltammetry at a hanging mercury drop electrode. The influences of various operational conditions on the stripping response were examined. The optimum accumulation potentials and accumulation times were -0.40 V and up to 60 sec for pinazepam, -0.60 V and up to 40 sec for camazepam, -0.40 V and up to 30 sec for bromazepam and -0.60 V and up to 60 sec for BrTDO, respectively. The effects of various urine components on the voltammetric response were also studied, and preliminary separation of the drugs was found necessary because of interference by creatinine and uric acid. The proposed method is appropriate for the determination of the four drugs in urine up to the 1000 ng/ml level with short accumulation periods (10-60 sec). The relative standard deviation for the 500 ng/ml level of the drugs in urine (30-sec accumulation) was less than 3%.