J.-C. Vire

Voltammetric oxidation of trazodone

The electrochemical behavior of trazodone (TRZ), 2-{3-[4-(m-chlorophenyl)-1-poperazinyl] propyl}-1,2,4-triazolo-[4,3 a]pyridin-3(2H)-one hydrochloride has been investigated in aqueous media as a function of pH by cyclic voltammetry, coulometry and exhaustive electrolysis at solid electrodes. The evolution of the uv-spectrum during electrolysis and TLC of the organic extracts have been realized. Interpretation of the results and a comparative study of a trazodone metabolite 1-m-chlorophenylpiperazine dihydrochloride (mCPP) have permitted the elucidation of the redox behaviour of trazodone, to point out different oxidation sites and distinct electrochemical processes depending on the pH of the solution. Quantitative measurements of trazodone within the range 1 × 10−4 M−1 × 10−6 M have bee realized at the carbon paste electrode (cpe using the different pulse technique.

Voltammetric Behavior and Simultaneous Determination of the Antioxidants Propyl Gallate, Butylated Hydroxyanisole, and Butylated Hydroxytoluene in Acidic Acetonitrile-Water Medium Using PLS Calibration

The voltammetric behavior of propyl gallate (PG), butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) has been studied at the glassy carbon electrode (static and rotating), in an acetonitrile-water medium using LS, sampled DC, DP and cyclic voltammetry. The use of a Britton-Robinson buffer (pH 2.8) containing 20 % of acetonitrile together with the sampled DC mode allows one to analyze binary and ternary mixtures of these antioxidants by applying a PLS type 1 multivariate approach. After optimization of the parameters of the chemometric procedure, the proposed method was validated with synthetic samples and applied for the determination of these antioxidants in different spiked samples of packet soup.

Polarographic behaviour and hydrolysis of midazolam and its metabolites

Abstract The electrochemical behaviour of midazolam [7-chloro-5-(o-fluorophenyl)-3H-(2′- methyllimidazo) [1,5-a]-benzodiazepine was studied by polarography and cyclic voltammetry. The irreversible two-electron were is not strongly affected by the imidazole ring or the 5-o-fluorophenyl substituent, but the latter increases the rate of the hydrolysis in acidic media. Kinetic parameters are evaluated for midazolam and three of its hydroxylated metabolites. The hydrolysis is a first-order reaction initially but becomes second order. The 3-hydroxy matabolites are more easily hydrolyzed than midazolam. Midazolam (10−4–10−7 M) can be quanitified by using differential-pulse polarography; the detection limit is 6 × 10−8 M.

Adsorptive stripping voltammetry applied to drug analysis: a powerful tool.

A brief review of the principles and instrumentation of adsorptive stripping voltammetry is presented and the advantages of the method are described. As for many highly sensitive techniques applied to the analysis of complex media, severe interferences may occur. Different approaches can be used to circumvent these problems, exemplified by several applications in biological fluids. The application of modified electrodes to enhance selectivity is discussed.

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.

Voltammetric and chromatographic assay of trazodone

Abstract Trazodone, a triazolopyridine derivative with antidepressant activity, is irreversibly oxidized in two steps in a large range of scan rates. The first peak shows a linear dependence on trazodone concentration. This behaviour is used for analytical purposes in determining trazodone concentrations in commercial preparations. An original alternative gas-liquid chromatographic method is also developed. Comparison of the chromatographic with voltammetric methods shows that a) both are sensitive enough to be applied to single tablet assays; b) the major advantage of the voltammetric method for analytical purposes lies in the rapid determination of the trazodone content in tablets. Preparation of the samples is easy and no extraction procedure is required.

Electrochemical Study and Hydrolysis Kinetic of Imidazo-and Triazolobenzodiazepines

Abstract Polarographic and cyclic voltammetric techniques have been used to determine the electrochemical behaviours of imidazo-and triazolobenzodiazepines and to carry out a kinetic study of the hydrolysis reaction occuring in acid medium. The reduction process is not strongly affected by the substituents, except in the case of a 3-hydrozy substitution giving rise to a four-electron transfer. Hydrolysis kinetic parameters however are highly dependent on the presence of the imidazole or the triazole ring, on the 5-o-phenyl substituent and the 3-hydroxy group. Quantitative studies have been performed, showing that midazolam as well as triazolam can be determined up to 1.10−7 M using d.p. polarography.

Nouveau Modele d'Electrode Modifiee a Base de Carbone et de Polymere

Abstract A new type of modified electrode is proposed, based on the thermosealing of carbon and a polymer in different proportions. The mode of preparation and the performances of this new model of polymer electrode are described in details. The potential range is larger than with other electrodes, particularly in the anodic range. Some performances realized on the behaviour of pharmaceutical compounds are described.

Copper (II), Lead (II) and Cadmium (II) Complexes with the Antiinflammatory Drugs Piroxicam and Tenoxicam

Abstract The chelating tendency of the antiinflammatory drugs piroxicam and tenoxicam towards copper (II), lead (II) and cadmium (II) ions has been investigated using both differential pulse polarography and cyclic voltammetry and the stability constants of the formed complexes have been compared. The effect of the nature of the supporting electrolyte, the pH and other parameters have also been considered. Tenoxicam exhibits relatively stronger chelating properties than piroxicam towards each ion despite of their structural similarity.

Polarographic Behaviour of Trazodone

Abstract Trazodone, which cannot be electrochemically reduced at the dropping mercury electrode, exhibits catalytic proton reduction waves as shown by the strong modifications occuring with variations of pH, concentration, nature of the buffer, ionic strength and presence of organic solvent. The catalytic process is developing three successive waves with rising pH or concentration, depending on the protonation rate or the adsorbed state. The influence of sodium ions indicates a decrease of sorbtivity with the proton concentration. The strong surface character of the wave observed in very acidic media decreases gradually on behalf of a more pronounced bulk character with increasing pH. The wave recorded in neutral media is of analytical interest, a linear calibration curve being plotted in the 2.10−6 M to 1.10−3 M concentration range.