Desenvolvimento de um eletrodo compósito à base de grafite e policaprolactona aplicado para a determinação de anti-hipertensivos

Abstract

In this work, we present a new composite material obtained by the use of polycaprolactone (PCL), a biodegradable polymer and graphite. The composite electrodes (CE) were made in the proportions of 30 to 80% (mass of graphite). The electrochemical electrode performance was evaluated in cyclic voltammetry. The graphite content was determined by thermogravimetry. The interaction between the phases was evaluated by infrared spectroscopy. The 70% CE presented the best results in terms of voltammetric response and mechanical polishing. So, the 70% composite was also characterized by Raman spectroscopy and atomic force microscopy. The electrode presented a wide useful range of potential, at different pH values and solutions as support electrolyte. The analytical application of 70% CE, of electroactive area of 0.134 cm2

, was evaluated for the individual and simultaneous determination of antihypertensives drugs. Amlodipine (AML), used mainly in the treatment of hypertension and angina and hydrochlorothiazide (HCTZ), a thiazide diuretic used to treat high blood pressure. Differential pulse voltammetry was used for CE application. The working conditions were obtained using Britton-Robinson buffer 0.04 mol L-1

pH 5.0 as support electrolyte, with pulse amplitude of 100 mV, scanning increment of 10 mV, pulse time of 0.05 seconds and 20 mV s-1

of scan rate. In order to improve an application of CE, sodium dodecyl sulfate (SDS) was used in electroanalysis. The CE response was compared to that of a glassy carbon electrode and presented higher signal intensity for the AML and HCTZ binary determination. The simultaneous analytical curve was obtained in the concentration range of 7.3 × 10-7

– 2.6 × 10-6 mol L-1

(n = 5, r = 0.998) and 2.4 × 10-6

- 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. The CE was successfully applied for the determination of AML or HCTZ in pharmaceutical samples and for simultaneous determination of AML and HTZ in synthetic urine samples. The proposed material demonstrates attractive properties for a CE, such as low cost, simple construction and fast in electroanalytical analyzes.