VOLTAMMETRIC STUDY OF THE DIURETIC XIPAMIDE

The oxidative behaviour Of -chloro-5-sulfamylsalicyloyl-2',6'-dimethyl amilide (xipamide) was studied in aqueous alcoholic media (9:91 MeOH H2O, pH 1-7.5) and two different ionic media (KNO3 and KCl) at carbon electrodes. The oxidation process has been shown to be irreversible a nd predominantly diffusion controlled over the entire pH range and in both media. A voltammetric method was developed at pH 2.5 (phosphate b uffer) and 0.4 M KNO3 for the quantitative determination of xipamide. The peak current showed a linear relationship with concentration in th e range 4.65 X 10(-7)-2.88 X 10(-5) M with detection limits of 6.76 x 10(-8) M (24 ppb) by differential pulse voltammetry and 3.94 x 10(-7) M (140 ppb) by linear scan voltammetry, and a reproducibility (in term s of relative standard deviation) of 5.8% and 6.3% for 10 determinatio ns of concentrations of 1.41 x 10(-5) M and 7.05 x 10(-8) M respective ly. The method for xipamide was applied to assays of pharmaceuticals ( Demiax 20 mg) and spiked urine samples.