Pesticide residues in dry herbs used for tea preparation by UHPLC-MS/MS: Method validation and analysis

Dry herbs are used for tea preparation and as material for phytotherapy medicines, and both are widely used by the population. However, herbs may contain contaminants and residues that could pose a health risk to consumers, and their levels should be monitored. In this work, a multiresidue method was validated for the analysis of 65 pesticides in different dry herbs. The samples were extracted with acidified acetonitrile, MgSO4 and CH3COONa, purified by dispersive solid phase with PSA, and the pesticides were quantified by UHPLC-MS/MS. A mixture of seven herbs composed of different plant parts was used as a control for method validation. Recovery ranged from 70 to 120% with a few exceptions; repeatability and intermediate precision was below 20% for most compounds. Limit of quantification (LOQ) ranged from 0.005 to 0.100 mg kg-1. The method was applied for the analysis of 75 samples of 33 different dry herbs. In total, 26 samples (34.6%) were positive for at least one pesticide (≥ limit of detection), from which 19 samples had residues at quantified levels (≥ LOQ; up to 1.60 mg kg-1). Carbendazim and imidacloprid were the pesticides most detected (38.7 of all samples and 30.7% of positive samples, respectively). Only two of the analyzed pesticides are registered in Brazil for use in the investigated herbs, indicating that good agricultural practices are not being applied in herb cultivation in the country. A risk assessment for the consumption of chamomile tea containing fenpropathrin was conducted and did not indicate any health concern for consumers.