Determination of Triazole Derivative Metabolites in Fruit and Vegetables using the QuPPe Method and Differential Mobility Spectrometry
One of the largest and most important pesticide groups are the triazole-fungicides. They are employed for the control of a wide range of fungal diseases on fruit, vegetables, nuts, pulses, grain and seed crops and act systemically. Compounds such as triadimefon, cyproconazole, propiconazole, epoxiconazole and tebuconazole all contain the 1,2,4-triazole moiety and metabolize to 1,2,4-triazole (TRZ) and to three more common metabolites, namely 1,2,4-triazole alanine (TA), 1,2,4-triazole acetic acid (TAA), and 1,2,4-triazole lactic acid (TLA). These four main common metabolites of triazole fungicides are known as triazole derivative metabolites (TDMs).
TDMs are very polar by nature and their analysis is very challenging. The use of isotopically labeled internal standards (IL-IS) helps to eliminate quantitation errors related to matrix-effects and has opened the way for a straightforward sample preparation via the QuPPe method, without any cleanup step. Direct analysis of TDMs by LC-MS/MS, however, has proven to be difficult due to strong signal interferences caused by co-eluting peaks, which strongly compromise the LOQs and the accuracy. To improve selectivity Differential Mobility Spectrometry (DMS), a variation of Ion Mobility Spectrometry (IMS), was employed. Using DMS, recovery experiments at 0.01, 0.1 and 0.2 mg kg-1 in fruit and vegetables and at 0.02, 0.2 and 0.4 mg kg-1 in milk and rice resulted in highly satisfactory recovery and precision figures overall. TRZ, the least sensitive among the TDMs, partly failed to comply with the precision criteria at the lowest spiking level. More than 4600 conventional and organically labelled products from the local market were analyzed for TDM residues with high percentages of the samples being found to contain residues exceeding the LOQ. TA was the TDM compound most frequently detected. Roughly half of the conventional and one third of the organically labelled products contained it at levels ≥LOQ. TLA and TAA were also frequently found whereas TRZ exceeded the LOQ only rarely. Our findings suggest a long persistence of the TDM-moiety in the environment.
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Published 04-04-2016, 08:12:53
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