Determination of fungicides in white grape bagasse by pressurized liquid extraction and gas chromatography tandem mass spectrometry

Ultrasound-assisted extraction (UAE) and pressurized liquid extraction (PLE) followed by gas chromatography–triple quadrupole-mass spectrometry (GC TQ-MS) were used for the rapid determination of 11 fungicides (metalaxyl, cyprodinil, procymidone, iprovalicarb, myclobutanyl, kresoxim-methyl, benalaxyl, fenhexamide, tebuconazole, iprodione and dimethomorph) in white grape bagasse. The extractions were optimized on real non-spiked samples by means of experimental design and the optimal conditions were selected to achieve the method validation. The PLE procedure showed much higher efficiency than UAE for the target fungicides. Under the selected extraction conditions, PLE showed satisfactory linearity, repeatability and reproducibility. Recoveries for the majority of studied fungicides were higher than 80% with relative standard deviations (RSD) lower than 12%. Limits of detection (LODs) for GC TQ-MS were very low, at the sub ng g−1 for the majority of the target fungicides, well below the European maximum residue limits (MRLs) for wine and table grapes, and vine leaves. Eighteen white grape bagasse samples were analyzed and nine out of eleven targets were detected in the samples. Seven of them were detected in more than 50% of the samples and most samples contained at least four of the target analytes. The most frequently found compounds were tebuconazole and dimethomorph with concentrations between 1.6–130 and 2.0–1788 ng g−1, respectively. Some samples showed high levels of many of the studied fungicides (high ng g−1, even μg g−1 for cyprodinil, fenhexamide, iprodione and dimethomorph), but all of them below the European maximum residue limits (MRLs) for wine grapes.