Simple one-step extraction and cleanup by pressurized liquid extraction for gas chromatographic–mass spectrometric determination of pesticides in green leafy vegetables

Determination of veterinary drug/pesticide residues in livestock and poultry excrement using selective accelerated solvent extraction and magnetic material purification combined with ultra-high-performance liquid chromatography-tandem mass spectrometry

An ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method based on selective accelerated solvent extraction and magnetic material purification was established to analyze the residues of various veterinary antibiotics and agricultural fungicides and insecticides in livestock and poultry excrement. Methanol-acetonitrile (4:1, V/V) was used as the extraction solvent and static extraction was conducted three times in 5 min. Preliminary purification was achieved by adding 0.5 g acidic alumina-florisil (1:1, W/W) to the extraction cell while the extraction was conducted. This preliminarily-purified extract was further purified using magnetic material, then analyzed using UPLC-MS/MS. Under optimal conditions, 33 types of antibiotics, including 3 amphenicols, 8 macrolides, 17 sulfonamides and 5 nitroimidazoles, as well as 37 types of pesticides, including 27 insecticides and 10 fungicides, were detected. Recoveries ranged from 60.3% to 110.0% at three spiked concentrations (10 μg/kg, 20 μg/kg and 50 μg/kg), the detection limits ranged from 0.2 to 3.5 μg/kg and the quantitative limits ranged from 0.5 to 11.5 μg/kg. This newly-established method was tested using 30 livestock and poultry excrement samples and confirmed its use for determining veterinary drugs and pesticides in practical samples.

Current mass spectrometry strategies for the analysis of pesticides and their metabolites in food and water matrices

Analysis of pesticides and their metabolites in food and water matrices continues to be an active research area closely related to food safety and environmental issues. This review discusses the most widely applied mass spectrometric (MS) approaches to pesticide residues analysis over the last few years. The main techniques for sample preparation remain solvent extraction and solid-phase extraction. The QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) approach is being increasingly used for the development of multi-class pesticide residues methods in various sample matrices. MS detectors-triple quadrupole (QqQ), ion-trap (IT), quadrupole linear ion trap (QqLIT), time-of-flight (TOF), and quadrupole time-of-flight (QqTOF)-have been established as powerful analytical tools sharing a primary role in the detection/quantification and/or identification/confirmation of pesticides and their metabolites. Recent developments in analytical instrumentation have enabled coupling of ultra-performance liquid chromatography (UPLC) and fast gas chromatography (GC) with MS detectors, and faster analysis for a greater number of pesticides. The newly developed "ambient-ionization" MS techniques (e.g., desorption electrospray ionization, DESI, and direct analysis in real time, DART) hyphenated with high-resolution MS platforms without liquid chromatography separation, and sometimes with minimum pre-treatment, have shown potential for pesticide residue screening. The recently introduced Orbitrap mass spectrometers can provide high resolving power and mass accuracy, to tackle complex analytical problems involved in pesticide residue analysis.

Application of gas chromatography/tandem quadrupole mass spectrometry to the multi-residue analysis of pesticides in green leafy vegetables

A new, sensitive and specific method has been developed for the simultaneous determination of 129 pesticides in lettuce and other green leafy vegetables. The samples were extracted with acetonitrile and co-extractives such as fatty acids and pigments were removed using dispersive solid-phase extraction (dispersive-SPE) with primary secondary amine (PSA) and graphitized carbon black (GCB). All pesticides were analyzed in a single injection gas chromatography/tandem quadrupole mass spectrometry (GC/MS/MS) acquisition method. Two multiple reaction monitoring (MRM) transitions of precursor ions fragmenting into product ions were recorded for the targeted pesticides, thus fulfilling the EU identification points system criteria for the identification of contaminants (2002/657/EC). Calibration curves were determined using matrix-matched standards, and exhibited excellent linearity at two orders of magnitude from 0.005 to 0.5 mg/kg for almost all the pesticides studied (R(2) > or = 0.99). The analytical performance was demonstrated by the analysis of lettuce samples spiked at five concentration levels ranging from 0.005 to 0.5 mg/kg for each pesticide. The recovery and repeatability results satisfied SANCO/2007/3131 criteria (i.e. average recoveries were in the range 70-120% with RSDs < or =20%) for 114 of the 129 pesticides at the 0.005 mg/kg spiking level, and for almost all pesticides at the higher spiking levels. The methodology was applied successfully to identify and quantify pesticide residues in leafy vegetable samples such as lettuce, cabbage and leek.