Comparative Study of Basal-Plane Pyrolytic Graphite, Boron-Doped Diamond, and Amorphous Carbon Nitride Electrodes for the Voltammetric Determination of Furosemide in Pharmaceutical and Urine Samples
Résumé
Sensitive and simple electroanalytical methods were developed for the determination of the loop diuretic
furosemide (FUR) in pharmaceutical formulations and synthetic urine samples by coupling square-wave
voltammetry (SWV) with polished basal-plane pyrolytic graphite (BPPG) or cathodically pretreated
boron-doped diamond (BDD) and amorphous carbon nitride (a-CNx) as working electrodes. The
analytical parameters obtained with the three methods were compared. With BPPG, best results were
attained using 0.10 mol L1 H2SO4 as supporting electrolyte, whereas with BDD and a-CNx, this was
attained using a 0.040 mol L1 BR buffer (pH 4.5). Cyclic voltammograms obtained for FUR evidenced an
irreversible behavior (with two oxidation peaks), in agreement with the literature. On the BDD and a-CNx
electrodes, the electrooxidation of FUR is a purely diffusion-controlled process, whereas on the BPPG
electrode some degree of adsorption is also involved. The obtained linear response ranges (detection
limits) for the BPPG, BDD, and a-CNx electrodes were 0.60–4.8 (0.47), 0.30–13 (0.30), and 0.50–99 (0.39)
mmol L1, respectively. The proposed methods were successfully applied in the determination of FUR in
pharmaceutical formulations (tablets), with results similar to those obtained using a reference
spectrophotometric method (at a confidence level of 95 %), and in the recovery of FUR in synthetic urine
samples. The analytical conditions obtained with the novel SWV methods here reported are
comparatively better than those for other electrochemical methods in the literature. As the pretreatment
procedures are much simpler for BDD and a-CNx than for BPPG, one can conclude that the former two
materials can be advantageously used to determine FUR with good sensitivity and selectivity.