Direct determination of free amino acids and sugars in green tea by anion-exchange chromatography with integrated pulsed amperometric detection

• Published in: Journal of Chromatography A 2002-12, Vol.982 (2), p.237-244
• Main Authors: Ding, Yongsheng, Yu, Hong, Mou, Shifen
• Format: Article
• Language: English
• Subjects: Amino acids; Amino Acids - analysis; Anion Exchange Resins; Biological and medical sciences; Carbohydrates; Carbohydrates - analysis; Chromatography, Ion Exchange - methods; Coffee, tea and other stimulative beverage industries; Electrochemistry - methods; Food industries; Fundamental and applied biological sciences. Psychology; Reproducibility of Results; Sensitivity and Specificity; Tea - chemistry
• ISSN: 0021-9673
• DOI: 10.1016/S0021-9673(02)01650-3

Determination of amino acids and sugars in green tea by anion-exchange chromatography with integrated pulsed amperometric detection was developed. Amino acids and sugars were separated on an anion-exchange column at a flow-rate of 0.25 ml/min by using ternary gradient elution consisting of deionized water, 0.25 M sodium hydroxide, and 1.0 M sodium acetate. Under optimized conditions, theanine was separated from glutamine and three sugars (glucose, fructose, and sucrose) were eluted earlier than the neutral amino acids to avoid their interference with each other. RSDs of the peak area of analytes were lower than 4.6%. Detection limits for the analytes ranged from 0.12 to 4.9 pmol. The linearities for all analytes were two or three orders of magnitude with the correlation coefficients greater than 0.99. This method was applied to determination of amino acids and sugars in green tea with satisfactory results.