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%.
A new method for the simultaneous separation and determination of mercury(II) with other heavy and transition metals by ion chromatography (IC) was developed. This method involves on-column derivatization with 2,6-pyridinedicarboxylic acid (PDCA) and anion-exchange separation, followed by a post-column reaction with 2-[(5-bromo-2-pyridyl)-azo]-5-diethylaminophenol (5-Br-PADAP) to form metal-5-Br-PADAP chelates, which can be sensitively monitored by spectrophotometric detection at 565 nm. PDCA was first combined with Na 2 C 2 O 4 to separate the metals within 16 min. The optimum separation and derivatization conditions were studied in detail. The detection limits of Pb 2+ , Cu 2+ , Ni 2+ , Zn 2+ , Co 2+ , Cd 2+ , Mn 2+ and Hg 2+ were 0.2 mg l −1 (115 l loop), 1.5, 5, 0.5, 5, 5, 3 and 20 g l −1 (676 l loop), respectively. This method was applied to the analysis of standard rice sample, waste cellpacking and municipal solid waste fly ash with satisfying results.
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