Horseradish Peroxidase Electrode for the Analysis of Clozapine

Abstract

A horseradish peroxidase (HRP) immobilized electrode was developed for the assay of the antipsychotic compound clozapine (CLZ). The biosensor was made of HRP crosslinked with glutaraldehyde and bovine serum albumin (BSA) and blended in the electrode matrix. The latter was a carbon paste based on solid paraffin and graphite particles. A dialysis membrane was secured at the tip of the enzyme based electrode. Cyclic voltamperometry at the solid carbon paste electrode (sCPE) permitted to point out a reversible pattern for CLZ electrooxidation attributed to a relatively stable nitrenium ion. The formation of the latter and of a newly generated species, was inferred at the biosensor. The electroreduction of these generated species was performed at the biosensor at an applied potential of 0.0 V vs. Ag/AgCL 3 M KCl. Several experimental parameters influencing the biosensor response were studied such as pH, buffer composition, and detection potential. The resulting biosensor offered, at pH 4.5 in Britton–Robinson buffer (BRb) in the presence of 0.1 mM H2O2 and at 0.0 V vs. Ag/AgCl, a linear response in the concentration range comprized between 1.0 × 10−6 M and 1 × 10−5 M with a detection limit of 1.7 × 10−7 M and a quantification limit of 5.6 × 10−7 M. In addition to the mechanistic information provided, the biosensor was found useful for the determination of CLZ in tablets. The accuracy of the assay was checked by capillary electrophoresis (CZE).