Abstract

SPECTROPHOTOMETRIC DETERMINATION OF PYRIMETHAMINE IN PURE AND PHARMACEUTICAL FORMS

P. Saritha* T. Charan Singh and C. Gyana Kumari

ABSTRACT

Four simple, sensitive and accurate methods (I, II, III and IV) for the quantitative estimation of Pyrimethamine in both pure and pharmaceuticals have been developed, optimized and validated. Method I is based on the interaction of the drug (Pyrimethamine) with TCNE, whereas Method II on that with p-chloranilic acid, while Method III on the same with iodine to form ion pair charge transfer complexes. The anions of these reagents absorb at their characteristic wavelengths (TCNE – 400 nm and 420 nm, p-chloranilic acid–540 nm and iodide – 366 nm) whose absorbance linearly varies with the concentration of the drug and forms a basis for its estimation. Method IV is based on the interaction of the drug with bromocresol green (BCG) to form chloroform extractable ion pair complex which absorbs maximally at 415 nm whose absorbance too linearly varies with the concentration of the drug and forms a basis for its estimation. Factors affecting the absorbance are optimized and all the methods have been validated in terms of ICH guidelines.

Keywords: Pyrimethamine (PYM), TCNE (Tetracyanoethylene), p-Chloranilic acid (p- CL), Iodine, Bromocresol green (BCG), Spectrophometry.