SPECTROPHOTOMETRIC ASSESSMENT OF VITAMIN B2 (RIBOFLAVIN) BY DIAZOTIZATION AND COUPLING REACTION WITH 2-AMINO-4-(3-PYRIMIDYL) PYRIMIDINE REAGENT

Objective: The diazotization and coupling method were employed as a simple and sensitive spectrophotometric analysis technique for the determination of riboflavin. Method: The method is based on the reaction between diazotization of the reagent using sodium nitrite in acidic medium and the maximum absorption wavelength of the resulting compound is 505 nm, since the compound is colorless and gets orange red when it couples with the medicine in basic medium. Stoichiometry of the produced compound was determined using the Job's method and mole-ratio method; the drug-to-reagent binding ratio was 1:1 by both methods. Results: Based on Beer's law, linearity in the concentration range of 1.25-29 µg/mL was observed. The molar absorptivity value is 8317.777 L .mol-1. cm-1, the coefficient of determination (R2) is 0.997, the relative standard deviation (RSD) is less than 0.12%, the limit of quantification (LOQ) is 0.263 µ g/mL, the limit of detection (LOD) is 0.087 µg/mL, and the Sandell's sensitivity value is 0.0452 µg/cm2. Novelty: The presented method was successfully applied for determination of riboflavin in pharmaceutical preparations.