A method for simultaneous detection of terbufos and its five metabolites in tea by multi-plug filtration cleanup (m-PFC) method combined with liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) was established. The pesticides in tea samples were extracted with acetonitrile after being fully wetted with water. Inorganic salts were added to the system to separate it into organic and aqueous phases. The upper fraction was purified on an m-PFC column before analysis by LC-MS/MS. The accurate quantification was performed by the matrix-matched external standard method. The results showed that the calibration curves for six pesticides (terbufos, terbufos sulfoxide, terbufos sulfone, terbufos-OXON, terbufos-OXON sulfoxide, and terbufos-OXON sulfone) had good linearity in the concentration range of 1–500 μg/L with correlation coefficients higher than 0.999. The detection limits were in the range of 0.001–0.01 mg/kg, and the quantitation limits were 0.002–0.03 mg/kg. The average recoveries at three spiked levels of 0.01, 0.50 and 2.00 mg/kg were in the range of 81.5%–103.9%, with relative standard deviations (RSDs) of 0.9%–10.1%. This method has the advantage of low cost and easy operation, and rapid analysis with good recovery and accuracy, and is suitable for simultaneous determination of the residues of terbufos and its metabolites in tea.

An analytical method was established for the simultaneous detection of five saccharides in tea by multi-plug filtration cleanup (m-PFC) combined with high performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD). An m-PFC cartridge with polyamide powder as sorbent was developed for sample pretreatment. Tea samples were extracted with water while shaking, and then back-extracted with dichloromethane for the removal of impurities. The upper phase was purified using the m-PFC column and detected by HPLC. Quantification was performed by the external standard method. The results showed that the logarithm of the peak areas was linearly related to the logarithm of the concentrations of rhamnose, fructose, glucose, sucrose, and maltose within the linear ranges tested, with correlation coefficients higher than 0.99. The limits of detection (LOD) were in the range of 0.04–0.1 g/100 g, and the limits of quantitation (LOQ) were 0.10–0.20 g/100 g. The average recoveries at three spiked levels were in the range of 91.0%–103%, with relative standard deviations (RSDs) of 1.0%–4.6%. This method has the advantages of simple operation and good purification effect, and is suitable for the quantitation of these five saccharides in tea.