Multiresidue method for trace pesticide analysis in honeybee wax comb by GC-QqQ-MS

The aim of this analytical study is to develop an improved multi-residue methodology of high sensitivity and expanded scope for pesticide residue analysis in honeybee wax combs. The method was validated for 160 pesticide residues (including acaricides, insecticides, fungicides and herbicides) gas chromatography amenable and covering a wide variety of polarity and chemical structure. This method of analysis applied gas chromatography coupled to a triple quadrupole mass spectrometer for the quantitative analysis of pesticide residues. The extraction procedure applied was based QuEChERs method allowing acceptable recoveries for most of the pesticides (98%), within the range 60–120% with an associated precision (RSD) <20%, at concentration levels of MQL of 10 µg kg−1 for all pesticides with the exception of 3,5-dichloroaniline and chlordane (20 µg kg−1). The expanded uncertainty of the results was ±35% on average (coverage factor k=2 for a confidence level of 95%). The chromatographic multi-residue method was applied to determine levels of pesticide residues in 50 honeybee wax comb samples randomly collected from different apiaries in Spain. A total of 32 pesticide residues (14 insecticides/acaricides, 10 insecticides, 6 fungicides and 2 herbicides) were detected in the samples. The highest pesticide concentrations were found for those with insecticide-acaricide activity like acrinathrin, chlorfenvinphos, coumaphos and fluvalinate-tau, some of them are mainly applied in apiculture for controlling the honeybee parasite Varroa destructor. The total load of pesticide residues ranged from 69 to 1000 µg kg−1 for 40% of the analysed samples, 22% contained pesticide residues in the ranges of 1000–2000 µg kg−1, 24% between 2000 and 5000 µg kg−1 and 14% of the samples contained residues between 5000 and 9557 µg kg−1.EEA ConcordiaFil: Gil García, M.D. Universidad de Almería. Departamento de Química y Física. Campus de Excelencia Internacional en Agroalimentación; España. European Union Reference Laboratory for Pesticide Residues in Fruit and Vegetables; EspañaFil: Uclés, Samanta. Universidad de Almería. Departamento de Química y Física. Campus de Excelencia Internacional en Agroalimentación; España. European Union Reference Laboratory for Pesticide Residues in Fruit and Vegetables; EspañaFil: Lozano Fernández, A.B. Universidad de Almería. Departamento de Química y Física. Campus de Excelencia Internacional en Agroalimentación; España. European Union Reference Laboratory for Pesticide Residues in Fruit and Vegetables; EspañaFil: Sosa, Alexis Lionel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Concordia; ArgentinaFil: Rodríguez Fernández-Alba, Amadeo. Universidad de Almería. Departamento de Química y Física. Campus de Excelencia Internacional en Agroalimentación; España. European Union Reference Laboratory for Pesticide Residues in Fruit and Vegetables; Españ

Matrix interference evaluation employing GC and LC coupled to triple quadrupole tandem mass spectrometry

Gas and liquid chromatography coupled to triple quadrupole tandem mass spectrometry are currently the most powerful tools employed for the routine analysis of pesticide residues in food control laboratories. However, whatever the multiresidue extraction method, there will be a residual matrix effect making it difficult to identify/quantify some specific compounds in certain cases. Two main effects stand out: (i) co-elution with isobaric matrix interferents, which can be a major drawback for unequivocal identification, and therefore false negative detections, and (ii) signal suppression/enhancement, commonly called the “matrix effect”, which may cause serious problems including inaccurate quantitation, low analyte detectability and increased method uncertainty. The aim of this analytical study is to provide a framework for evaluating the maximum expected errors associated with the matrix effects. The worst-case study contrived to give an estimation of the extreme errors caused by matrix effects when extraction/determination protocols are applied in routine multiresidue analysis. Twenty-five different blank matrices extracted with the four most common extraction methods used in routine analysis (citrate QuEChERS with/without PSA clean-up, ethyl acetate and the Dutch mini-Luke “NL” methods) were evaluated by both GC-QqQ-MS/MS and LC-QqQ-MS/MS. The results showed that the presence of matrix compounds with isobaric transitions to target pesticides was higher in GC than under LC in the experimental conditions tested. In a second study, the number of “potential” false negatives was evaluated. For that, ten matrices with higher percentages of natural interfering components were checked. Additionally, the results showed that for more than 90% of the cases, pesticide quantification was not affected by matrix-matched standard calibration when an interferent was kept constant along the calibration curve. The error in quantification depended on the concentration level. In a third study, the “matrix effect” was evaluated for each commodity/extraction method. Results showed 44% of cases with suppression/enhancement for LC and 93% of cases with enhancement for GC.EEA ConcordiaFil: Uclés, Samanta. Universidad de Almería. Departamento de Química y Física. Campus de Excelencia Internacional en Agroalimentación; España. European Union Reference Laboratory for Pesticide Residues in Fruit and Vegetables; EspañaFil: Lozano Fernández, A.B. Universidad de Almería. Departamento de Química y Física. Campus de Excelencia Internacional en Agroalimentación; España. European Union Reference Laboratory for Pesticide Residues in Fruit and Vegetables; EspañaFil: Sosa, Alexis Lionel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Concordia; ArgentinaFil: Parrilla Vázquez, Piedad. Universidad de Almería. Departamento de Química y Física. Campus de Excelencia Internacional en Agroalimentación; España. European Union Reference Laboratory for Pesticide Residues in Fruit and Vegetables; EspañaFil: Valverde García, Antonio. Universidad de Almería. Departamento de Química y Física. Campus de Excelencia Internacional en Agroalimentación; España. European Union Reference Laboratory for Pesticide Residues in Fruit and Vegetables; EspañaFil: Rodríguez Fernández-Alba, Amadeo. Universidad de Almería. Departamento de Química y Física. Campus de Excelencia Internacional en Agroalimentación; España. European Union Reference Laboratory for Pesticide Residues in Fruit and Vegetables; Españ