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Titrimetric And Spectrophotometric Determination Of Salbutamol Sulphate In Pharmaceuticals Using Chloramine-T And Two Dyes

K.Basavaiah, B.C.Somashekar, V. Ramakrishna

Four new methods are described for the assay of salbutamol sulphate(SBS) in bulk drug and in dosage forms using chloramine-T and two dyes, methyl orange and indigocarmine, as reagents. In direct titrimetry (method A), aqueous solution of SBS is titrated with chloramine-T(CAT) in hydrochloric acid medium and in the presence of excess of potassium bromide, using methyl orange indicator. Back titrimetry(method B) involves treating of SBS with a measured excess of chloramine-T in hydrochloric acid medium, and after the oxidation of SBS is judged to be complete, the unreacted oxidant is determined iodometrically, In both methods, the reaction follows a 1:2 (SBS:CAT), reaction stoichiometry method A is applicable over 2.5-9.5 mg, and 3-10 mg of SBS can be determined by method B. Spectrophotometric methods entail the addition of a known excess of CAT to SBS in hydrochloric acid medium followed by determination of residual oxidant by reacting with a fixed amount of either methyl orange and measuring the absorbance at 520 nm (Method C) or indigo carmine and measuring the absorbance at 610 nm (Method D). In all the methods, the amount of CAT reacted corresponds to the amount of SBS. In spectrophotometric methods, the systems obey Beer’s law for 0.5-4.5 and 1.25-12.5 μg/ml for method C and method D, respectively. Apparent molar absorptivity values are calculated to be 6.89×104 (method A) and 2.46×104 l/mol/cm (method B). The limits of detection and quantification are reported for both methods. Intra-day and inter-day precision and accuracy of the developed methods were evaluated. The methods were successfully applied to the assay of SBS in tablet and capsule formulations and the results were compared with those of a reference method by applying Student’s t-and F-tests. No interference was observed from common tablet adjuvants.