HPLC-photolysis-electrochemical detection in pharmaceutical analysis: application to the determination of spironolactone and hydrochlorothiazide in tablets

To extend the applicability of electrochemical detection in pharmaceutical analysis, an on-line postcolumn photochemical reactor is used to produce electroactive photoderivatives of selected cardiovascular drugs. This system is applied to the analysis of dosage forms containing spironolactone in both single-component formulation and in combination with hydrochlorothiazide. The pH of the mobile phase and irradiation time within the reactor are optimized to produce maximum amperometric response. Spironolactone, hydrochlorothiazide, and 4-amino-6-chloro-1,3-benzenedisulfonamide, the synthetic precursor and hydrolysis product of hydrochlorothiazide, are separated by reversed-phase chromatography on a 5-microns cyano bonded phase column within nine minutes by using a methanol-phosphate buffer mobile phase. Minimum detectable levels are in the low ng range.