The free amino acids in five Dancong Oolong tea were identified and quantitatively determined by ultra-high pressure liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF MS), and the effects of chromatographic separation conditions and mass spectrometry parameters on the determination of amino acids in Dancong Oolong tea were investigated. The samples were extracted with hot water, separated by a HILIC column, and gradient elution was performed with 20 mmol/L ammonium formate (containing 0.1% formic acid) and acetonitrile (containing 0.1% formic acid) as mobile phase. Full information mass spectrometry elevated (MSE) with electrospray positive ion mode (ESI+) was used to detect the amino acids and data collection, and quantitative analysis was performed by matrix matching standard curve method. Results showed that the acquisition mode of mass spectrometry significantly influenced the abundance and quantity of the precursor ion and fragment ion peak, and there was a good linear relationship between the concentration of 22 amino acid standards and detection response, and the correlation coefficients were greater than 0.99. The detection limit (LOD) for analysts was in the range of 1.3-95.7 μg/L, and the optimized UHPLC-HRMS method was successfully applied to the analysis of amino acids in Oolong tea samples due to the high accuracy, precision and repeatability. And the total amount of free amino acids in Dancong Oolong tea was in the range of 485.12-575.95 mg/100 g. The five Dancong Oolong tea, such as Wuye, Yashixiang, Yulanxiang, Baiye, Shuixian, contained a variety of common amino acids, while the contents of different amino acids showed significant difference (P<0.05), in which the contents of theanine, glutamate, arginine, serine and aspartic acid were higher compared with control.
WANG Zhonghe
,
LI Xiaoting
,
HU Wenmei
,
WANG Jun
. Determination of amino acids in Oolong tea by ultra-high pressure liquid chromatography coupled with high resolution mass spectrometry[J]. Food and Fermentation Industries, 2020
, 46(21)
: 207
-214
.
DOI: 10.13995/j.cnki.11-1802/ts.024239
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