Journal of Chromatography A, 1216 (2009) 3702–3709 Contents lists available at ScienceDirect Journal of Chromatography A journal homepage: www.elsevier.com/locate/chroma Dispersive solid-phase extraction followed by liquid chromatography–tandem mass spectrometry for the multi-residue analysis of pesticides in raw bovine milk Thierry Dagnac a,∗ , Maria Garcia-Chao a , Paula Pulleiro a , Carmen Garcia-Jares b , Maria Llompart b a INGACAL (Galician Institute for Food Quality)-CIAM (Agrarian and Agronomic Research Centre), Laboratory of Food/Feed Safety and Organic Contaminants, Apartado 10, E-15080 A Coru˜ na, Spain b Departamento de Quimica Analitica, Nutricion y Bromatologia, Instituto de Investigacion y Analisis Alimentario, Campus Sur, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain article info Article history: Received 10 September 2008 Received in revised form 4 February 2009 Accepted 16 February 2009 Available online 21 February 2009 Keywords: Raw milk Pesticides Liquid chromatography Triple quadrupole mass spectrometry Dispersive solid-phase extraction abstract A fast multi-residue method based on dispersive solid-phase extraction (DSPE) followed by liquid chromatography–tandem mass spectrometry was developed for the simultaneous determination of 44 pesticides in raw bovine milk. Raw bovine milk samples did not percolate through SPE cartridges usually applied for pesticide extraction from homogenized pasteurized milk samples. Therefore, a DSPE tech- nique was implemented and validated for the first time in this work. Graphitized non-porous carbon and C18 modified silica materials were tested both in combination with magnesium sulfate and bonded silica with ethylenediamine-N-propyl phase. The efficiency of the DSPE process was studied at several concentration levels obtaining the higher recoveries with C18 material. The method performance was also assessed and the limits of quantification reached the ng g -1 level, complying with the most recent maximum residue levels. The DSPE method was also shown to be suited to both the fatty and skimmed fractions issued from raw milk. Finally, the extraction method was successfully applied to the analysis of raw milk samples collected in 23 farms of dairy cattle from NW Spain (Galicia). © 2009 Elsevier B.V. All rights reserved. 1. Introduction Studies focussing on the assessment of pesticide exposure and on the adverse effects of pesticides on both human health and the environment are a matter of a growing scientific and public concern [1,2]. Milk-producing animals, such as cows, may accu- mulate residues of these pesticides through carry over processes from contaminated feed, grass and corn silage, water, top-layer soil and inhaled air. As a result, residues of some harmful pesti- cides can be detected in raw bovine milk samples [3–5]. To protect consumers and to promote trade, legal MRLs (maximum residue levels) have been established for residues of pesticides on products of plant and animal origin that are intended for human or animal consumption [6]. New rules applicable from September 1, 2008 set fully harmonised MRLs of pesticides in the European countries [7–9]. For the past three decades, organophosphorus pesticides (OPPs) have been the insecticides most commonly used by both profes- ∗ Corresponding author. Tel.: +34 981 64 79 02; fax: +34 981 67 36 56. E-mail addresses: thierry.dagnac@xunta.es, tdagnac@netcourrier.com (T. Dagnac). sional pest control bodies and homeowners [10]. Nevertheless, the decision of the US Environmental Protection Agency (EPA) to phase out certain uses of the organophosphorus insecticides because of their potentially toxic effects to humans has led to their gradual replacement by pyrethroid insecticides. Although OPPs are less stable and persistent than organochlorinated pesticides, they can covalently link to some milk proteins and some studies report their presence in cow milk [11–13]. Other classes of herbicides such as triazines, phenylureas and chloroacetanilides are commonly spread in corn parcels where the entire crop is intended for bovine feed after silage processes. They are then likely to be present in corn silage along with their metabo- lites. The amended European Union legislation has just established MRLs for some of these herbicides in milk and dairy products and 25 of the 44 pesticides included in the present work have now specific MRLs between 0.01 and 0.1 mg kg -1 [14]. According to the Commission decision (97/747) [15,16] fixing the levels and frequen- cies of sampling provided by the Council Directive (96/23) for the monitoring of certain substances and residues thereof in certain animal products, bovine milk samples must be taken only from raw milk. To achieve effective extractions of pesticides from milk sam- ples, several sample preparation methods have been developed 0021-9673/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2009.02.048