Streamlining sample preparation and gas chromatography–tandem mass spectrometry analysis of multiple pesticide residues in tea

• Published in: Analytica chimica acta 2012-09, Vol.743, p.51-60
• Main Authors: Cajka, Tomas, Sandy, Chris, Bachanova, Veronika, Drabova, Lucie, Kalachova, Kamila, Pulkrabova, Jana, Hajslova, Jana
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chemistry Techniques, Analytical; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Gas chromatographic methods; Gas chromatography; Gas chromatography (GC); Gas Chromatography-Mass Spectrometry; Liquid-liquid extraction; Mass spectrometry; Mathematical analysis; Pesticide residues; Pesticide Residues - analysis; Pesticides; Recovery; Residues; Sample preparation; Spectrometric and optical methods; Tandem Mass Spectrometry; Tandem mass spectrometry (MS/MS); Tea; Tea - chemistry
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2012.06.051

[Display omitted] ► We developed a new sample preparation method for the rapid analysis of pesticide residues in tea. ► QuEChERS-based extraction followed by LLE cleanup enabled good recoveries and minimisation of matrix co-extracts. ► Hydration of matrix is crucial for efficient extraction of target analytes. ► GC–MS/MS enabled simultaneous determination of target analytes. 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 1mgkg−1. Under optimised GC–MS/MS conditions, most of the analytes gave lowest calibration level ≤0.01mgkg−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.