Effectiveness of pressurized liquid extraction and solvent extraction for the simultaneous quantification of 14 pesticide residues in green tea using GC

A simultaneous multiresidue method to determine 14 different pesticides, namely: flufenoxuron, fenitrothion, chlorfluazuron, chlorpyrifos, hexythiazox, methidathion, chlorfenapyr, tebuconazole, EPN, bifenthrin, cyhalothrin, spirodiclofen, difenoconazole, and azoxystrobin in green tea using pressurized liquid extraction (PLE) is described and compared with that of liquid-liquid extraction (LLE). For PLE, the extraction conditions were not optimized. Rather they were selected based upon previous successful investigations published by our laboratory. Analysis was performed by GC with electron capture detector (GC-ECD), and the pesticide identity of the positive samples was confirmed by GC-MS in a selected ion-monitoring (SIM) mode. Calibration curves showed an excellent linearity for concentrations ranging from 0.006 to 36.049 ppm, with r(2) > 0.995. Green tea spiked at each of the two fortification levels, yielded average recoveries in the range of 87-112% and 71-109% for PLE and LLE, respectively. Precision values, expressed as RSDs, were below 6% at various spiking levels. With respect to the existing procedures, both methods gave LCQs that were lower than the maximum residue limits (MRLs) established by the Korea Food and Drug Administration (KFDA). Both methods have been successfully applied to the analysis of real samples, and bifenthrin was the only pesticide residue quantified in incurred green tea samples, with concentrations ranging from 0.093 ppm (LLE) to 0.1 ppm (PLE). These concentration levels were relatively low compared to KFDA-MRL (0.3 ppm). According to the validation data and performance characteristics, both methods are appropriate for multiresidue analysis of pesticide residues in green tea. PLE methodology showed superiority in recoveries of some pesticides, acceptable accuracy and precision while minimizing environmental concerns, time, and labor, and can be applied in routine analytical laboratories.