Simple and Improved Visible Spectrophotometric Method for Determination of Paracetamol Using Sodium Nitroprusside Chromogenic Reagent

Abstract

A simple, rapid and improved visible spectrophotometric method has been proposed for determination of paracetamol (N-acetyl-p-aminophenol) in bulk drug. The experiment is based on the alkaline hydrolysis of paracetamol (PCT) to p-aminophenol (PAP) at elevated temperature and subsequent derivatization of PAP with sodium nitroprusside (SNP) at room temperature to produce an intense green colored N-nitrosyl-O-nitrosyl-p-aminophenol chromophore for direct determination of PCT at 685 nm. The molar absorptivity and Sandell's sensitivity are observed as 5.933x10 4 L.mol-1 .cm-1 and 0.0252 µg. cm-2 respectively for the chromophore. Beer's law is obeyed over the concentration range of 15-120 µg with linear regression equation as A= 0.009+0.003C (µg at 10 mL dilution). The percent recovery was found in the range 100.07-100.60%. The average of relative error and relative standard deviation are observed as 0.252% and 0.406% respectively. Reaction mechanism and reaction stoichiometry of the chromophoric reaction are discussed. The parameters with regard to determination of paracetamol by proposed method are optimized. Drugs like ibuprofen, aspirin and metformin do not interfere hence the proposed method is suitable for determination of PCT impurity in the said drugs.