Analytical Sciences

Spectrophotometric Determination of Certain Vicinal Dihydroxybenzene Derivatives in Pharmaceutical Preparations

Babu G. GOWDA, Mahaveer B. MELWANKI, and Jaldappa SEETHARAMAPPA 

Department of Chemistry, Karnatak University, Dharwad-580 003, India

A simple, rapid and sensitive spectrophotometric method for the assay of certain adrenergic drugs, [pyrocatechol (PC), levodopa (LD), methyldopa (MD) and dopamine (DP)] is described. The method involves the oxidation of o-dihydroxybenzene derivatives by K₂CrO₄ followed by oxidative coupling with sulfanilic acid (SPA), leading to the formation of a red or violet colored product having maximum absorbance at 490 - 495 nm for LD, MD and DP or at 560 nm for PC. This method has been successfully applied to the determination of LD, MD and DP in tablets and injections of pharmaceutical preparation. The common excipients do not interfere with the proposed method. A statistical comparison of these results with those of a reported method shows good agreement and indicates no significant difference in precision.

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