Abstract: An analytical method for the determination of underivatized amino acids was established with high performance liquid chromatography (HPLC) coupled with evaporative light-scattering detection (ELSD). A domestic evaporative light-scattering detector was used to determine underivatized amino acids. A BISCHOFFTM C18 AQ PLUS column and a solvent gradient elution with 0.2% heptafluorobutyric acid containing 0.1% trifluoroacetic acid as mobile phase A and methanol as mobile phase B were used. The temperature of the drift tube in ELSD was 40 ℃ and the flow rate of dry air was 2.5 L/min. The logarithm of the peak area and logarithm of the mass of each separated amino acid was in good linearity. The linear ranges of the 20 amino acids were from 30~300 mg/L. The limits of detection (S/N＞3) for the underivatized amino acids were from 24 ng to 100 ng. The average recoveries of the 20 amino acids were between 90.6% and 106.0%. This method and system are simple, rapid and accurate for the determination of underivatized amino acids. It can be used for the determination of underivatized amino acids in pharmaceutical, food and chemical industry fields.

Key words: amino acids, evaporative light-scattering detection (ELSD), injection, reversed-phase high performance liquid chromatography (RP-HPLC), underivatized amino acids