Elucidation of False Detection of Pesticides During Residue Analysis in Indian Tobacco by Multidimensional GC-MS

Abstract

False detection of pesticides in agricultural produce may raise serious questions regarding both consumer safety and trade. High levels of delta-hexachlorocyclohexane (δ-HCH; 11.7-22.3 mg/kg) were detected in some tobacco samples in a retention time-based GC analysis. Hence, the selection of an appropriate analytical method is an uncompromisable necessity. Objectives: This research work aimed to elucidate false detection of pesticides along with identification of coeluting tobacco matrix compounds to understand the dynamics of false detection with an increase in the number of analyzed pesticides and to screen suitable analytical methods. Methods: Initially, retention time-based GC analysis was performed for monitoring of 10 pesticide residues in tobacco leaf matrix, followed by GC-MS/selected-ion monitoring (SIM) analysis. Then, the total number of pesticides to be analyzed was increased to 47, and residue analysis was performed by involving GC-MS/SIM and multidimensional (MD) GC-MS. Results: A false-positive detection of δ-HCH due to a coeluting tobacco aroma compound, neophytadiene, during residue analysis of 10 pesticides in tobacco (Nicotiana tabacum L.) leaf was observed. This problem was resolved by employing the unique quantifier and qualifier ions in SIM mode. However, with 47 pesticides, neophytadiene completely masked the signal of δ-HCH, which resulted in an impure spectrum of δ-HCH (<30% similarity match) even after application of selective quantifier and qualifier ions. Finally, MDGC-MS analysis could resolve it by chromatographic separation of the said analyte from the coeluting matrix compound. Conclusions: The findings of this work offer the potential to minimize false reporting of target pesticides to comply with consumer safety and trade standards. Highlights: The study identifies various tobacco matrix compounds coeluting with pesticides during multiresidue analysis. Neophytadiene, a tobacco aroma compound, resulted in false-positive detection of δ-HCH. The MDGC-MS could be effectively used as a confirmatory analysis tool for reliable detection of pesticide residue in tobacco leaf matrix.