A new sensitive spectrophotometric determination of sodium 2-mercaptoethanesulfonate using leuco xylene cyanol FF

A simple and accurate spectrophotometric method for determination of sodium 2-mercaptoethanesulfonate (MESNa) with leuco xylene cyanol FF (LXCFF) has been developed. The proposed method is based on the reaction of MESNa with potassium iodate(V) in acidic medium to liberate iodine, which oxidizes leuco xylene cyanol FF to its blue form xylene cyanol FF. The xylene cyanol FF dye formed shows maximum and stable absorbance at pH 4.1–4.2. Absorbance of the obtained colored products was measured at 613 nm. The molar absorptivity, limit of detection and limit of determination of the method were found to be 3.64 × 10⁴ L/mol cm, 0.29 and 0.33 μg/mL, respectively. The colour system obeys Beer’s laws in the range 0.4–4.0 μg/mL of MESNa. All the variables were studied in order to optimize the reaction conditions. The procedure was used for determination of MESNa in pharmaceutical preparations. Reliability of determination was confirmed applying standard iodometric method, recommended by European and Polish Pharmacopoeia.