In this work, a new rapid method for the determination of 135 pesticide residues in green and black dry
tea leaves and stalks employing gas chromatography coupled to tandem mass spectrometry (GC–MS/MS)
with a triple quadrupole was developed and validated. A substantial simplification of sample processing
prior to the quantification step was achieved: after addition of water to a homogenised sample, transfer of
analytes into an acetonitrile layer was aided by the addition of inorganic salts. Bulk co-extracts, contained
in the crude organic extract obtained by partition, were subsequently removed by liquid–liquid extraction
using hexane with the assistance of added 20% (w/w) aqueous NaCl solution. The importance of matrix
hydration prior to the extraction for achieving good recoveries was demonstrated on tea samples with
incurred pesticide residues. For most of the analytes, recoveries in the acceptable range of 70–120%
and repeatabilities (relative standard deviations, RSDs)
≤20% were achieved for both matrices at spiking
levels of 0.01, 0.1 and 1 mg kg−1. Under optimised GC–MS/MS conditions, most of the analytes gave lowest
calibration level
≤0.01 mg kg−1, permitting the control at the maximum residue levels (MRLs) laid down
in Regulation (EC) No 396/2005. The developed method was successfully applied to the determination
of pesticide residues in real tea samples.