Solid-Liquid Extraction with Low-Temperature Partitioning as an Alternative to Determinate Pesticide Residues in Teas

Methods used to determine pesticide residues in teas typically require several laborious steps for sample preparation before analysis. In this study, a simple method based on solid-liquid extraction with low-temperature partitioning (SLE/LTP) and analysis by gas chromatography coupled to mass spectrometry (GC-MS) was optimized and validated for the determination of pesticide residues (pirimiphos-methyl, flutriafol, cyproconazole, and bifenthrin) in dehydrated green tea leaves. After low-temperature partitioning (LTP), the extract in acetonitrile was subjected to a clean-up step using primary secondary amine (PSA) and octadecylsilane (C18) as sorbents for chlorophyll removal. The optimized SLE/LTP-GC-MS method was validated, and it proved to be effective and selective for extracting pesticides from green tea samples, presenting limit of detection (LOD) and limit of quantification (LOQ) of 0.015 and 0.050 mg kg^-1, respectively. Recovery ranged between 81-111%, coefficients of variation were less than 16% and coefficients of determination (R²) were greater than 0.990. The optimized and validated method was applied to green tea and 13 other tea varieties sampled in South and Southeast regions of Brazil. The pesticides under study were detected in some of those samples at values higher than the maximum residue limits (MRLs) allowed by the European Union.

Keywords:
SLE/LTP; chromatography coupled with mass spectrometry; method validation; sample preparation; residue analysis; Camellia sinensis