Accurate determination of pesticide residues incurred in tea by gas chromatography-high resolution isotope dilution mass spectrometry

Abstract

This paper presents the development of a precise and accurate analytical method for the determination of 12 incurred pesticides in tea using gas chromatography-high resolution isotope dilution mass spectrometry. The extraction efficiency of accelerated solvent extraction (ASE) was evaluated in which four extraction parameters, solvent, temperature, number of static cycles and static time for spiked and incurred samples, have been investigated systematically. The optimized solvent and temperature were found to be an acetone–n-hexane mixture (2 : 1, v/v) and 120 °C for both spiked and incurred samples. However, it was found that the number of static cycles and static time for the spiked tea sample were different from that for the incurred sample. Two cycles of 5 min each were set for the extraction of pesticides from the spiked tea, while two cycles of 10 min each were set for extraction from the incurred sample. The overall average recoveries using this method at three spiked concentration levels (50, 200, 1000 ng g⁻¹) ranged from 95.96% to 102.04%, and relative standard deviations (RSDs) were in the range 0.83–3.12% (n = 6) for all analytes. The limits of detection (LODs) ranged from 0.02 to 10.83 ng g⁻¹, and the limits of quantification (LOQs) ranged from 0.09 to 38.74 ng g⁻¹. The RSDs (n = 6) of two incurred tea samples were in the range 1.04–2.93%, and 1.01–2.96%, respectively, which are better than those obtained using a QuEChERS-GC/MS/MS method. This indicates that the developed method is more suitable for the precise determination and research of pesticides incurred in tea.