In Situ Spectrodensitometric Determination of Methyl and Propyl Parabens, Benzoic and Sorbic Acids in Bulk Powder, Foods, and Pharmaceutical Formulations

ATLC spectrodensitometric procedure was developed for the determination of methyl paraben, propyl paraben, sorbic acid and benzoic acid as bulk powders or in pharmaceutical dosage forms and foods. The procedure was used for the determination of the two parabens singly or together and also was used for the determination of benzoic and sorbic acids singly because they were found singly in some commercial food and pharmaceutical products. The cited compounds were separated on silica gel with fluorescent indicator in systems, acetone-ethanol-aqueous ammonia 28%-ethyl acetate (84:3:9:9) for the determination of benzoic and sorbic acids and n-hexane-ethyl acetate-acetic acid (80:5:20) for the determination of the two parabens. Absorbance measurement (detection of reflectance) of separated compounds was carried out in situ, at 254 nm for the two parabens, sorbic acid, and at 228 nm for benzoic acid using multilevel calibration curves in the concentration ranges of 0.2—2.5 μg/spot, 0.5—3 μg/spot, and 2.5—12.5 μg/spot for sorbic acid, the two parabens, and benzoic acid, respectively. The results were evaluated by linear regression analysis. The mean % accuracies were found to be, mean ±C.V.(%), 99.65 ±0.963, 99.45±1.02, 99.60±0.825 and 99.34±0.969 for benzoic acid, sorbic acid, methyl paraben and propyl paraben in bulk powders, respectively. While in case of benzoic and sorbic acids in foods the mean % accuracies were found to be: 97.72±1.231 and 98.81±1.296, respectively. The mean % accuracies of methyl paraben, propyl paraben, sorbic acid in pharmaceutical dosage forms were found to be: 98.19±0.874, 97.830±0.799 and 98.36±0.572, respectively.