No abstract

A high-performance anion-exchange chromatographic method for the simultaneous separation and determination of four artificial sweeteners (sodium saccharin, aspartame, sodium cyclamate and acesulfame-K) and citric acid in a single injection is proposed. The separation was performed by an anion-exchange gradient program and determination by ultraviolet absorbance detection for sodium saccharin, aspartame, acesulfame-K in combination with conductivity detection for sodium saccharin, sodium cyclamate, acesulfame-K as well as citric acid in series. Good linearities between the concentrations of all analytes and relevant peak area responses were achieved over the range 2-100 ~g/ml. The detection limits (signal-to-noise ratio 3:1 ) were 0.019 Ixg/ml for sodium saccharin, 0.035 Ixg/ml for aspartame, 0.044 txg/ml for acesulfame-K by ultraviolet absorbance detection and 0.26 p.g/ml for sodium saccharin, 0.16 Ixg/ml for sodium cyclamate, 0.23 Ixg/ml for acesulfame-K and 0.22 ixg/ml for citric acid by conductivity detection. The method has been successfully applied to the determination of the four sweeteners and citric acid in drinks and powdered tabletop sweeteners, and the average recoveries for various samples ranged from 93 to 107%.

Two ion chromatographic methods have been proposed for the simultaneous determination of caffeine, theobromine and theophylline. The separations were based on isocratic elutions and the determinations on ultraviolet absorbance detections at 274 nm. The detection limits (signal-to-noise ratio 3:1) for the three compounds were all below sub-mg ml À1 level. The methods have been successfully applied to the determination of these three compounds in foods and pharmaceutical preparations, and the average recoveries for various samples ranged from 87% to 103%. In addition, the retention mechanisms of these three compounds on various ion-exchange resins were discussed. The results obtained revealed that ion-exchange chromatography is possibly a good alternative to conventional liquid chromatography for the separation and determination of some water-soluble, neutral organic molecules with a certain hydrophobicity. #