RAPID TITRIMETRIC AND SPECTROPHOTOMETRIC ASSAY METHODS FOR THE DETERMINATION OF LAMIVUDINE IN PHARMACEUTICALS USING IODATE AND TWO DYES

摘要

One titrimetric and two spectrophotometric methods which are simple, sensitive and rapid, are described for the assay of lamivudine in bulk drag and in tablet dosage forms using potassium iodate and two dyes, methyl orange and indigocarmine. as reagents. In titrimetry, aqueous solution of lamivudine is titrated directly with iodate in acidic medium, and in the presence of excess of bromide using methyl orange as indicator. After the decolouration of red colour of methyl orange, the residual bromine is titrated iodometrically to a starch end point. Spectrophotometric methods involve the addition of a known excess of iodate in acidic medium and in the presence of excess of bromide followed by the determination of residual bromine by the reaction witha fixed amount of either methyl orange and measuring the absorbance at 520 nrn (method A), or indigo carmine and measuring the absorbance at 610 nm (method B). In all the methods, the amount of iodate reacted corresponds to the amount of lamivudine content. Titrimetric method is applicable over 1.5-8.0 mg range. The systems obey Beer's law for 0.5-5.0 mug/mL (method A) and 1.25-12.5 mug/mL (method B). The calculated apparent molar absorptivity values are found to be 3.3 x 10~4 and 9.3 x 10 L mol~(-1) cm~(-1), for method A and method B. respectively, and the corresponding Sandell sensitivity values are 6.94 and 24.62 ng/cm~2. The limits of detection and quantification are also reported for both spectrophotometric methods. Intra-day and inter-day precision and accuracy for the developed methods have been evaluated. The methods were successfully applied to the assay of lamivudine in tablet formulation and the results were compared with those of a reference method by applying Student's t-test and F-test.No interference were observed from common tablet adjuvants. The accuracy and reliability of the methods were further ascertained by recovery experiments using standard addition technique.