Rapid and Sensitive Spectrophotometric Measurement of Non-Specific Beta Blocker Propranolol Hydrochloride Using Three Sulphonphthalein Dyes In Pure Form, Pharmaceuticals and Human Urine

Three sensitive, selective, rapid and easily reproducible spectrophotometric methods (A-C) have been developed for the determination of propranolol hydrochloride (PPH) as a hydrochloride free base propranolol (PPL) in bulk sample and in its dosage forms. These methods are based on ion-pair formation between propranolol as a hydrochloride and free base and three acidic (sulphonphthalein) dyes; namely bromothymol blue (BTB), bromocresol green (BCG) and bromocresol purple (BCP) which induces an instantaneous bathochromic shift of the maximum in the drug spectrum. The colored products are measured at 420 nm (PPL-BTB complex and PPL-BCP complex) and 425 nm (PPL-BCG complex). The reactions were extremely rapid at room temperature and the absorbance values remained constant for 90 min (method B), and over 24 hrs (method A and C). Conformity to Beer’s law in the range 0.4-7.0 μg ml -1 for methods A and B and 0.5-8.4 μg ml -1 for method C enabled the assay of dosage forms of the drug. The proposed methods were compared with a reference method; the results obtained were of equal accuracy and precision. In addition, these methods were also found to be specific for the analysis of PPH in the presence of excipients, which are co-formulated in the drug. Satisfactory results were obtained when applied to spiked human urine. A more detailed investigation of the propanolol hydrochloride ion pair complexes were made with respect to its composition indicated by stability constant values.