Batch injection analysis with electrochemical detection for the simultaneous determination of the diuretics furosemide and hydrochlorothiazide in synthetic urine and pharmaceutical samples

This works shows the combination of batch-injection analysis with multiple-pulse amperometric detection (BIAMPA) for the determination of the diuretics furosemide (FRD) and hydrochlorothiazide (HCT) in urine and pharmaceutical samples. Under optimized electrolyte conditions (0.04 mol L-1 Britton-Robinson buffer solution at pH 4.0) FRD was oxidized at + 1.10 V and both compounds were oxidized at + 1.30 V. The MPA detection involves the continuous application of two potential pulses as a function of time to determine FRD at the first potential and HCT at the second after subtracting the FRD current obtained at the second potential. A correction factor was needed because the current of FRD at both potentials was different. A boron-doped diamond working electrode was selected for the simultaneous determination as its surface is less susceptive to fouling. The compounds exhibited a linear response range of 2 to 100 mu mol L-1 for HCT (r = 0.9990) and 2 to 300 mu mol L-1 for FRD (r = 0.9993), satisfactory repeatability (RSD lower than 5% for n = 30), detection limits of 0.65 mu mol L-1 for FRD and 0.63 mu mol L-1 for HCT, and analytical frequency of 130 injections per hour. The proposed method was applied for the analysis of synthetic urine samples spiked with both compounds and proper recovery values were obtained (95-110%), confirming the potential application for anti-doping analyses. Moreover, the proposed method was compared to UV-Vis spectrophotometry for the analysis of pharmaceutical formulations and they were found to be statistically similar at the 95% confidence level.