Neutral red dye as a novel reagent in spectrophotometric determination of Doxycycline via oxidation and bleaching color of the dye

Abstract

A simple and accrued spectrophotometric method was developed to estimate Doxycycline as pure and in its formulation. The method included using a novel reagent neutral red dye the present method. The method was based on the oxidation of Doxycycline with an excess amount of N-bromosucinimide in an acid medium, then the residual amount of N-bromosucinimide oxidized the neutral red dye and caused bleaching of the color of the dye. The absorbance of the dye's color did not bleach measured at wavelength 525 nm. The absorbance is proportional to the concentration of Doxycycline in the solution. The linearity was from 1 to 15 µg/ ml, and the higher concentration above 15 µg/ ml gave deviation from Beer's law. The important analytical parameter included molar absorptivity and Sandell's sensitivity index, which were calculated and equal to 3.67 x104 l/mol.cm, 0.01261µg/cm2, respectively. An application part included estimating Doxycycline in its dosage form (capsule) from different manufacturers with satisfactory results. Keywords: Doxycycline, Neutral red, Bleaching Color, Oxidation,