TWO SELECTIVE SPECTROPHOTOMETRIC METHODS FOR THE DETERMINATION OF THIORIDAZINE HYDROCHLORIDE IN TABLETS AND IN BIOLOGICAL FLUIDS

Two simple, rapid and selective spectrophotometric methods have been developed for the analysis of the psychoactive drug thioridazine HCl (TRH) in tablets and in biological fluids. The first method is based on the oxidation of TRH by a known excess of N-bromosuccinimide (NBS), followed by the determination of unreacted oxidants by measuring the decrease in absorbance of two different dyes; amaranth (AM) and methylene blue (MB) at a suitable lambda(max) 520 and 660 nm, respectively. Beer-Lambert plots showed good correlation in the concentration ranges of 0.8-4.8 and 0.8-5.6 mu g/ml for AM and MB methods, respectively. The second method is based upon the formation of an ion-pair complexes (1: 1) with the acidic sulphonphthalein dyes bromophenol blue (BPB) and bromothymol blue (BTB). The formed complexes were extracted into methylene chloride and their absorbance was measured at 405 and 408 nm for BPB and BTB, respectively. Beer's law was obeyed with a good correlation coefficient (r = 0.9995-0.9989) in the concentration ranges of 4-24 mu g/ml for both BPB and BTB methods, respectively. All measurements of the two procedures are carried out in an acidic medium at room temperature. Optimizations of the different experimental conditions are described for both methods. The two methods have been successfully applied to the determination of thioridazine HCl in pharmaceutical, serum and urine samples and average recoveries are in the range of 98.12 - 102.55\%. Analytical results obtained with this novel method are satisfactory.