Simultaneous RP-LC determination of additives in soft drinks

A reverse-phase HPLC method for the simultaneous determination of the main artificial sweeteners, preservatives and dyes present in soft drinks is proposed. It involves the use of a 10 mu m LiChrosorb RP18 column and a binary eluent consisting of aqueous 0.1 M phosphate buffer (pH 4.0) added with methanol, according to a suitable gradient elution program. Good separations were obtained within less than 20-min run-time, with a satisfactory precision. The sensitivity of spectrophotometric detection was optimised by adopting a wavelength switching technique, thus achieving for all the additives considered detection limits ranging from 0.1 to 3.0 mg L-1, well below the maximum permitted levels. The method was applied to some commercial soft drinks, whose analysis required minimum pre-treatment before direct injection.