Simultaneous determination of inorganic anions, organic acids, amino acids and carbohydrates by capillary electrophoresis

Abstract

A capillary zone electrophoretic method for the simultaneous analysis of inorganic anions, organic acids, amino acids and carbohydrates was developed with indirect UV detection using 2,6-pyridine dicarboxylic acid as the background electrolyte. This is the first paper to report their simultaneous analysis. Highly alkaline conditions were used in order to confer a negative charge not only on inorganic and organic anions but also on amino acids and carbohydrates, and to promote their migration towards the anode. Electroosmotic flow was reversed in the direction of the anode by adding cetyltrimethylammonium hydroxide to the electrolyte. Outstanding separations were obtained and electrophoretic mobilities of 82 compounds including nine inorganic anions, 23 organic acids, 18 amino acids and 32 carbohydrates were determined by the method. Under the optimized conditions 43 compounds were well separated in a single run. The relative standard deviations ( n=5) of the method were better than 0.5% for migration times and between 0.8% and 4.9% for peak areas except for a few compounds. The detection limits for anions and amino acids were in the range from 6 to 12 mg/l and for carbohydrates from 23 to 35 mg/l with 300 mbar·s pressure injection (6 nl) at a signal-to-noise ratio of three. This method could be readily applied to the simultaneous determination of inorganic anions, organic acids, amino acids and carbohydrates in soy sauce, nutrient tonic and pineapple.