Swift electrochemical sensing of diltiazem employing highly-selective molecularly-imprinted 3-amino-4-hydroxybenzoic acid

Abstract

Diltiazem is a calcium channel-blocking agent, efficient in treating various heart-related conditions and diseases. It has been used as a cutting agent in cocaine and prevents its common cardiotoxic effects. This paper presents a highly selective molecularly-imprinted sensor to detect diltiazem in buffer and urine. In addition, the possibility of using this sensor as a forensic tool for fingerprinting street-seized cocaine samples of heterogeneous composition was investigated. With thorough optimization of the fabrication process, it was possible to obtain a sensible and reproducible analytical signal via square-wave voltammetry (SWV) as the electroanalytical technique. The obtained analytical parameters for the samples in buffer, pH 7.4, were the limit of detection (LOD) of 0.12 µmol L−1, the limit of quantification (LOQ) of 0.41 µmol L−1, and inter-day reproducibility of 2%. For the samples in artificial urine, the analytical parameters were LOD of 0.26 µmol L−1, LOQ of 0.88 µmol L−1, and inter-day reproducibility of 9%. Decent linearity of the analytical signal with the increased concentration of diltiazem in the cocaine street samples suggested a high perspective of the proposed sensor for the forensic laboratory applications, more precisely, the determination of the seized samples' origins.