Spectrophotometric Method for the Determination of Tetracycline and Doxycycline by Oxidizing Coupling Reaction with 4-aminoantipyrine

Abstract

 A simple,  sensitive, accurate and low cost effective spectrophotometric method has been developed for the determination of Tetracycline and Doxycycline in pure and pharmaceutical formulations. The method is based on the reaction of methyldopa with 4-aminoantipyren (4-AAP) in presence of potassium ferriecyanide (PFC) in an alkaline medium. Two optimization methods were applied to determine the optimum conditions of oxidizing coupling reaction variables; univariate and design of experiment (DOE) method. The conditions effecting the  reaction; pH, buffer Volume,   reagent concentration, oxidant concentration, type of buffer, order of addition, time of reaction and stability were optimized . Under univariate and design of experiment (DOE) method; the Tetracycline colored product having (λmax) at 531nm 535nm. Beer’s law was obeyed in concentration range of [two scale (1-18 µg.mL-1) and (15-70µg.mL-1)] with correlation coefficient of 0.9997 and 0.9942 respectively and for second method [two scale (1-30 µg.mL-1) and (40-100µg.mL-1)] with correlation coefficient of 1 and 0.9913. The assay limits of detection quantification were 0.1732, 0.3123µg.mL-1 respectively. Under univariate the Doxycycline colored product having (λmax) at 515nm. Beer’s law was obeyed in concentration range (10-90 µg.mL-1) with correlation coefficient of 0.9995. The assay limits of detection quantification were 1.0724µg.mL-1. The method was successfully applied to the analysis of the drug tablets formulation.