Spectrophotometric Determination of Vitamin Folic Acid B9 in Some Drugs Using 1,2-Naphthoquine-4-Sulphonate (NQS)

Riyadh Radhi Al-Araji, Muthana Saleh Mashkour, Emad Abbas Jaffar Al-Mulla


In this study, simple and sensitive spectrophotometric method for the determination of folic acid (VB9) in pharmaceutical formulations was reported. The proposed method was based on the reaction between folic acid and 1,2-naphthoquine-4-sulphonate (NQS) at alkaline medium (pH 11) to form deep yellow product. Beer’s law was obeyed in the range of 0.75 - 10.5 μg/mL of folic acid at maximum wavelength of 436 nm. Under optimized reaction conditions, linear regression equation of the calibration curve was y = 0.048 x + 0.038 (μg/mL) with a linear correlation coefficient of 0.9988. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.159 μg/mL and 0.531 μg/mL, respectively. The method was successfully applied to the determination of folic acid in pharmaceutical formulations.