Quantitative Fluoro densitometric Determination of Quinine in Soft Drinks

Abstract

Abstract A quantitative fluorodensitometric method is described for the determination of quinine in soft drinks such as tonic water, lemonades, and fruit juices. This method is based on treatment of sample with an alkaline mixture of methanol-25% ammonia (485+15), followed by TLC analysis on silica gel G plates. The plates are developed with a mixture of chloroform-methanol-acetic acid (80+20+3) in saturated tanks. After development, the TLC plates are scanned with a reflectance flying-spot densitometer. The relationship between recorded peak area and concentration of bluish fluorescent standard spots is linear for 0.1–1.0 μg quinine. HCI.2H2O. Coefficients of variation of 2.0–2.5% are obtained for the fluorodensitometric determination of quinine in spiked tonic water as well as fruit juice. Results obtained in this study are compared with those found by methods prescribed by the AOAC, van Gils and Hidskes, and Hey. Coefficients of variation for the direct and indirect UV Spectrophotometric methods range from 0.75 to 1.40%. Recoveries of 96.9–100.7% are obtained for spiked beverages analyzed by either the densitometric or the Spectrophotometric methods. Despite its lower accuracy, the fluorodensitometric method is suitable as a screening procedure for routine analysis and is applicable to the determination of quinine in several types of soft drinks.