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

Abstract

• For the first time, an electrochemical molecularly-imprinted polymer was prepared for the selective detection of diltiazem, a calcium channel blocking agent. • GCE-MIP sensor was prepared by the electropolymerization of the 3-amino-4-hydroxybenzoic acid. • MIP fabrication procedure was thoroughly optimized giving reproducible, and repeatable analytical signal via square-wave voltammetry. • High linearity of the calibration curves with LOD of 0.12 and 0.26 μmol L −1 obtained for buffer and urine as the supporting electrolytes, respectively. • Possibility of using the optimized MIP for street-seized cocaine samples successfully demonstrated. 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.