Extraction of Bi(III) subsalicylate in micellar aggregation and its sustained release using an aqueous biphasic system

Bismuth (III) subsalicylate shows a characteristic absorption band at 300 ± 5 nm in polyethylene glycol (PEG) (50%, w/v) solution and could be determined spectrophotometrically at a trace concentration in PEG medium with a detection limit of 0.027 μg/L. The extraction of Bi (III) subsalicylate salt was studied using a simple aqueous biphasic system (ABS) composed of Na2SO4 (1.5 M) solution and 50% (w/v) aqueous PEG (#6000) solution at 300 K. Extraction was found to be quantitative at acidic pH (2-3). The aggregation numbers (Nagg) of micellar pristine solution of PEG, PEG rich phase extracted from ABS and the top phase of ABS containing bismuth subsalicylate (BSS) after extraction from different pH of the salt rich phase were studied. Kinetic spectrophotometric studies reveal that the BSS drug has a sustained release mechanism from the micellar medium of PEG solutions when added to a simulated gastric fluid. The results may have prospective pharmaceutical applications for a controlled drug release of BSS.