Sensitive Determination of Taurine, -Aminobutyric Acid and Ornithine in Wolfberry Fruit and Cortex Lycii by HPLC with Fluorescence Detection and Online Mass Spectrometry Identification

Abstract

A new, simple and highly sensitive method for the determination of taurine, γ-aminobutyric acid and ornithine using high-performance liquid chromatography (HPLC) with fluorescence detection is described. Three non-protein amino acids were derivatized by a novel precolumn derivatization reagent 2-[2-(dibenzocarbazol)-ethoxy]ethyl chloroformate before injected. Optimum derivatization was obtained at 40°C for 5 min in the presence of sodium borate buffer (pH 9.0). Derivatives were sufficiently stable to be efficiently analyzed by HPLC without pretreatment. On a reversed-phase Hypersil BDS C8 column, the amino acids were separated in conjunction with a gradient elution with a good baseline resolution. The identification of derivatives was carried out by online postcolumn mass spectrometry with an electrospray ionization source in positive ion mode. Excellent linear responses were observed with the correlation coefficients of >0.9996, and instrument detection limits (at a signal to noise of 3 : 1) were in the range of 0.30-0.33 nmol/L. The proposed method is sensitive and reproducible for the precise determination of the amino acids from wolfberry fruit and cortex lycii samples.