Abstract:
Objective
To apply high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) to the quantitative determination of trimethylsulfonium in retail tea products.
Methods
Trimethylsulfonium in tea product samples was extracted with heated mixed solution of acidic ammonium acetate and hydrogen peroxide. The extraction was purified with primary secondary amine, injected after passing hydrophilic membranes, and separated on hydrophilic column. The analyte was determined by HPLC-MS/MS in multiple reaction monitoring (MRM) mode and quantified by external matrix matched standard method. A total of 45 samples of retail tea products were detected.
Results
The calibration curve showed good linearity in the range of 0.032-1.00 μg/L with a correlation coefficient greater than 0.995. The limit of quantification (LOQ) and the limit of detection (LOD) were 10.0 μg/kg and 4.00 μg/kg, respectively. The average recoveries varied from 78.1% to 127.0% with the relative standard deviations (RSDs) of 3.9%-10.4% at three spiked levels (10.0, 20.0, and 40.0 μg/kg). Two samples were positive among the 45 samples, of which the trimethylsulfonium levels in jasmine tea and tieguanyin were 32.9μg/kg and 30.7μg/kg, respectively.
Conclusion
HPLC-MS/MS is a simple, accurate, and precise method to eliminate matrix in tea samples, with a limit of detection meeting relevant technical requirements; therefore, it is successfully applied to the determination of trimethylsulfonium in retail tea products.