Coomassie Brilliant Blue Staining Used in Spectrophotometric Assay for Dopamine Hydrochloride and Methyldopa Determination

Abstract

The catalytic oxidation reaction between Coomassie Brilliant Blue and N-bromosuccinimide was used in an acidic medium to develop a spectrophotometric method for the estimation of dopamine and methyldopa in their pure forms and in pharmaceutical preparations. The developed method exhibited high sensitivity, with molar absorptivity values of 1.77 × 104 and 2.97 × 104 L mol-1 cm -1 , and Sandell's sensitivity values of 0.0080 and 0.0107 mg cm-2 , respectively. The estimated quantities of dopamine hydrochloride and methyldopa were within the range of 0.5-18 μg/mL and 0.5-13 μg/mL, respectively. The developed method was successfully applied to tablet and injection formulations, and the results were in accord with the original drug content. The developed method was compared with standard addition and standard method in the British Pharmacopoeia, and no significant differences were revealed thus confirming the success of the developed method in the estimation of the studied drugs. Other statistical values were also studied .