Direct determination of fourteen underivatized amino acids from Whitmania pigra by using liquid chromatography-evaporative light scattering detection.

A new reversed phase high performance liquid chromatography-evaporative light scattering detection (RP-HPLC-ELSD) method has been developed for the direct determination of fourteen amino acids in Whitmania pigra, a commonly used traditional Chinese medicine (TCM). Simultaneous separation of these fourteen amino acids was achieved on a Prevail C18 column. Under the condition of gradient elution, the fourteen amino acids were separated within 25 min. The drift tube temperature of ELSD was set at 115 degrees C, and with the nitrogen flow rate of 2.5 l/min. All calibration curves showed good linear regression (r > 0.9975) within test ranges. The recoveries ranged from 94.8% to 104.4%. The limit of detection (LOD) for each compound was more than 20 mg/l at a signal to noise ratio (S/N) of 3. The validated method was successfully applied to quantify fourteen amino acids from Whitmania pigra, which provides a new basis of overall assessment on quality of Whitmania pigra.