Examination of Caffeine in Tea and Tea Drinks by Ultra-lipid Chromatography-tandem Mass Spectrometry

A new method,ultra-lipid chromatography-tandem mass spectrometry,which was used to exam the caffeine in tea and tea drinks,was developed in this experiment. After tea and tea drinks being pretreated,samples were separated by C₁₈ column and the column temperature was 25 ℃ with 0.1% formic acid solution-acetonitrile(80:20,v/v)as the mobile phase for gradient elution,and the flow rate was set at 0.3 mL/min. The electrospray ionization source of MS in positive ion mode was used for multiple reaction monitoring,under conditions included that desolvation gas(N₂)temperature was 500 ℃and the flow rate was 700 L/Hr,capillary voltage was 3.5 kV,cone voltage was 55 V and collision gas was high purity argon. Under conditions above,the limit of detection(LOD)of caffeine was 2.0 μg/L. There was a perfect linear relationship in relative concentration range(2.0~1000 μg/L),and the correlation(r)was 0.9969,average recoveries were in the range from 90.2% to 103.9%,and relative standard deviations(RSDs)were among 1.00% to 3.00%(n=6).The established method was convenient,fast and had good selectivity,good reproducibility and high sensitivity. It was suitable for quantifying caffeine in tea and tea drinks,the method was accurate and reliable,and had an advantage in detecting caffeine contained in complex samples.