Application of conventional (DC) and differential pulse polarography (DPP) to the quality control of benzothiadiazines in tablets. Simultaneous determination of hydrochlorothiazide and dihydralazine sulphate in mixtures with minimization of interaction by the use of a zero covariance in the calibration.

A previous study of the polarographic behaviour of 14 benzothiadiazines having diuretic properties enabled possible reaction mechanisms to be proposed and gave the opportunity to determine the best conditions for analytical application. The results obtained with benzthiazide as an example of the unsaturated compounds, bendrofluazide as the dihydro compound, and hydrochlorothiazide determined together with dihydralazine are reported. The electroactivity of these last two substances was made the object of a mathematical study for the correction of reciprocal interference.