Development of a composite electrode based on graphite and polycaprolactone for the determination of antihypertensive drugs

Abstract

A electrochemical sensor based on graphite and polycaprolactone (PCL), a biodegradable polymer, was developed for the first time. The electrodes were made in the proportions of 30–80% graphite-PCL w/w and characterized by thermogravimetric analysis (TGA), infrared spectroscopy, and cyclic voltammetry (CV). The composite of 70% graphite presented the best results, and it was also evaluated by Raman spectroscopy. The proposed electrode was successfully applied for the determinations of amlodipine (AML) or hydrochlorothiazide (HCTZ) in tablets and for the simultaneous determinations of AML and HCTZ in synthetic urine samples, using differential pulse voltammetry (DPV). The antihypertensive drugs showed oxidative peaks at 0.77 V for AML and at 0.98 V for HCTZ (vs. Ag|AgCl (3.0 mol L−1 KCl)). The simultaneous analytical curves were obtained in a Britton–Robinson buffer solution (pH 5.0) containing an anionic surfactant, sodium dodecyl sulfate (SDS) at a concentration of 2.0 × 10−4 mol L−1. The linearity ranges were 7.3 × 10−7 to 2.6 × 10−6 mol L−1 (n = 5,r = 0.998) and 2.4 × 10−6 to 2.2 × 10−5 mol L−1 (n = 5, r = 0.997) with detection limits of 6.8 × 10−8 and 2.7 × 10−7 mol L−1 for AML and HCTZ, respectively. Recoveries of these analytes in synthetic urine samples were 106.5% for AML and 103.2% for HCTZ.