Determination of hydrochlorothiazide in pharmaceutical preparations by time resolved chemiluminescence

A novel chemiluminescence method for the determination of hydrochlorothiazide (HCT) has been developed based on the reaction between Ce(IV) in acid medium with this diuretic agent in the presence of rhodamine 6G as sensitizer. The method described is based on the recording of the whole chemiluminescence intensityversus-time profile that enables the use of other measured parameters such as the total area that is proportional to the analyte concentration. The optimum chemical conditions for the chemiluminescence emission were investigated. Two determination approaches, intensity and area, were proposed. The calibration graphs were linear for the concentration range from 0.5 to 30 (mu)g ml^-1. The detection limits, according to Clayton et al. [Anal. Chem. 59 (1987)], were 0.34 and 0.16 (mu)g ml^-1, for intensity and area measurements, respectively. For analysis of 10 solutions of 7.5 and 20 (mu)g ml^-1 HCT, if error propagation theory is assumed, the relative error was less than 2%. The present chemiluminescence procedures were applied to the determination of HCT in Spanish pharmaceutical formulations, with excellent recoveries, as the determination is free from interference from common excipients and other drugs which also be present in the formulation.