Christine Petit

Horseradish peroxidase immobilized electrode for phenothiazine analysis

A horseradish peroxidase (HRP) immobilized carbon composite electrode has been developed for the amperometric study of phenothiazine analogues. Flow injection analysis and batch experiments have been realized in acetate buffer in the presence of hydrogen peroxide. Cyclic voltammetry and amperometry using a thin-layer flow cell (dual configuration, serial mode) have permitted one to suggest the mechanisms governing the biosensor signal at −0.1 V (vs. Ag/Ag+), in the presence of hydrogen peroxide, by addition of a phenothiazine derivative. It was inferred that electron transfer mediation by the phenothiazine occcurred at HRP/graphite adsorbed sites, in addition to peroxidation by dispersed HRP with substrate recycling at the graphite array-like structure of the biosensor. Thanks to these processes, high sensitivities were achieved especially in batch configurations, with amperometric detection capabilities down to 10−8 M in acetate buffer pH 4.7. Application of the biosensor to the determination of phenothiazines in drug formulations were realized.

Study of a new solid carbon paste tyrosinase-modified amperometric biosensor for the determination of catecholamines by high-performance liquid chromatography

Abstract The performance of a tyrosinase-modified “solid carbon paste” electrode (SCPE) as electrochemical detector has been studied in comparison with a glassy carbon electrode detector in high-performance liquid chromatography for the simultaneous determination of dopamine, 3,4-dihydroxyphenylacetic acid, norepinephrine and homovanillic acid. The influence of pH, flow-rate and amount of organic solvent in the mobile phase on the biosensor response was investigated. The stability and selectivity of the detector were significantly affected by the mobile phase pH. No effect of 2% isopropanol in the mobile phase was observed. The biosensor response was fast, reproducible, highly sensitive and linear over the concentration range 0.09 μM −1 m M (detection limit of ca. 290 pg of neurotransmitter injected).

Use of Immobilized Biological Compounds in Drug Analysis

Improvement in sensor technology, better control and understanding of the immobilization process of biological molecules along with pressing demands from the market side have stimulated research towards the development of sensors allowing selective, fast, and simple assays of therapeutic drugs. After showing several application fields for drugs analysis, a review of recently developed devices comprising immobilized biological materials for drug analysis is presented.