Validation of a microwave-assisted extraction gas chromatography detection method for the determination of fungicides in grapes

A microwave assisted extraction (MAE) method was developed for the simultaneous extraction of eight pesticides, vinclozolin, dichlofluanid, penconazole, captan, quinoxyfen, fluquinconazole, boscalid and pyraclostrobin, in grapes. The different parameters affecting the MAE method, such as temperature, extraction time and nature and volume of the extraction solvent, were evaluated. The experimental procedure was optimized using a multivariate statistical approach and the final analyses were carried out by gas chromatography-mass spectrometry (GC-MS). These eight fungicides could be efficiently extracted from 2.0 g of grapes with 10 mL of hexane/acetone (1 : 1, v/v) mixture at 105 °C in 10 minutes with microwave power set at 100% (600 W). Using the optimized conditions, the method was validated in terms of accuracy and precision. A matrix effect study was also carried out using different grape samples. Recoveries from spiked grape samples ranged from 82 to 107% and relative standard deviations were less than 10%. Detection and quantification limits ranged from 0.7 to 1.7 μg kg−1 and 2.2 to 5.8 μg kg−1, respectively, which were lower than the maximum residue limits of the pesticides in grape samples established by the European Union. Uncertainty assessment of measurement obtained by applying the proposed analytical method was estimated according to EURACHEM/CITAC guide. The expanded uncertainties were below 26% and 7% at two concentration levels, 10 and 50 μg kg−1, respectively.