Determination of Free Amino Acids in Tobacco Leaves by Reversed-Phase High Performance Liquid Chromatography

The free amino acids in tobacco leaves were extracted with ethanol, and purified by a cationic ion\|exchange resin column,then derived with o\|phthalaldehyde(OPA) and 9\|fluorenylmethylchloroformate(FMCF) in precolumn, and separated by reversed\|phase high\|performance liquid chromatography. Seventeen kinds of free amino acids were determined. The relative standard deviations of these amino acids were in the range of 3.0% to 7.0%, except that those of aspartic acid, glutamic acid and histidine were 8.0%, 8.6% and 9.0% respectively. The recoveries of these amino acids were from 81.0% to 110.5% with the exception of 68.0% for threonine, the mean recovery was 93.9%. The contents of free amino acids in tobacco leaves of different grades were determined by this method.