Determination of carbohydrates in food samples by capillary electrophoresis with indirect UV detection

An easy and reproducible capillary electrophoretic method with indirect UV detection for the determination of carbohydrates in food samples was described. A highly alkaline pH condition was used in order to charge every carbohydrate negatively. Electroosmotic flow (EOF) was reversed to detect sugar alcohols and to improve the separation of neutral and amino sugars. Under optimized conditions 28 carbohydrates including mono- and disaccharides, uronic acids, sialic acids, amino sugars and sugar alcohols were separated in less than 25 min. The detection limits for fructose, glucose and sucrose were in the range from 12 to 16 mg l−1 with pressure injection of 50 mbar for 6 s (ca. 6 nl) at a signal to noise ratio of 3. The calibration curves were linear over the range from 50 to 10 000 mg l−1 with correlation coefficients better than 0.9999. This method could be readily applied to the analysis of carbohydrates in several foods and beverages. Sample preparation was minimal and consisted either of dilution or dilution with filtration.