Talanta 73 (2007) 710–717 Transfer assessment of fipronil residues from feed to cow milk J. Le Faouder a , E. Bichon a , P. Brunschwig b,1 , R. Landelle c,2 , F. Andre a , B. Le Bizec a,∗ a LABERCA, Ecole Nationale V´ et´ erinaire de Nantes, Route de Gachet, Atlanpˆ ole La Chantrerie, BP 50707, 44087 Nantes Cedex 03, France b Institut de l’Elevage, 9 rue Andr´ e Brouard, 49100 Angers, France c Chambre d’Agriculture du Maine et Loire, Ferme Exp´ erimentale des Trinotti` eres, 49140 Montreuil-sur-Loir, France Received 24 November 2006; received in revised form 17 April 2007; accepted 30 April 2007 Available online 22 May 2007 Abstract Fipronil, a phenylpyrazole insecticide introduced for pest control on a broad range of crops, can also affect non-target insects such as honeybees. More widely, non-target environment such as milk produced by dairy cows fed with maize silage from treated seeds (=silage T) can be affected. To assess the potential transfer of fipronil residues (sulfone, sulfide, fipronil, desulfinyl and amide), a methodology including gas chromatography coupled with tandem mass spectrometry (GC–MS/MS) analysis was developed and validated according to the 2002/657/EC decision, in order to reach a level of quantification below 0.1 gL -1 in milk and 0.1 g kg -1 in plants. Twelve dairy cows were fed with silage T during 4 months. Concentration of fipronil in treated seeds was estimated at 1 g kg -1 , whereas silage from these seeds contained 0.30 ± 0.05 g kg -1 of dry material of fipronil, 0.13 ± 0.03 g kg -1 of dry material of sulfone. Sulfide residues were below the limit of quantification. Silage from untreated seeds (=silage U) presented traces of fipronil and sulfone, respectively at 0.04 ± 0.06 and 0.02 ± 0.03 g kg -1 of dry material. Contribution of fipronil residues from supplies was insignificant. During administration of silage T, only sulfone residues were quantified in milk. The average concentration was 0.14 ± 0.05 gL -1 . Before and after administration, sulfone residues were detected but not quantifiable (<0.025 gL -1 ). Our results suggest a transfer of fipronil from feed to milk under its sulfone form. Moreover, traces of fipronil residues in maize U, soya, wheat and straw show a diffuse contamination of this pesticide in the environment. © 2007 Elsevier B.V. All rights reserved. Keywords: GC–MS/MS; Transfer; Fipronil; Cow milk 1. Introduction Fipronil, (±)-5-amino-1-(2,6-dichloro-,,-trifluoro-p- tolyl)-4-trifluorom´ ethylsulfinyl – pyrazole-3-carbonitrile, a phenylpyrazol insecticide (Rhˆ one-Poulenc Agro) is used for the control of many soil and foliar insects on a variety of crops [1] and can also be formulated as flea and tick sprays for pets. However, fipronil is highly toxic to non-target environment and a lot of questions remain unanswered, particularly the one linked to the behavior of honeybees exposed to sublethal doses of fipronil [2–4]. In this survey, we focused on the study of milk, which can be considered as a non-target compartment when dairy cows ∗ Corresponding author. Tel.: +33 2 40 68 78 80; fax: +33 2 40 68 78 78. E-mail addresses: philippe.brunschwig@inst-elevage.asso.fr (P. Brunschwig), richard.landelle@maine-et-loire.chambagri.fr (R. Landelle), laberca@vet-nantes.fr (B. Le Bizec). 1 Tel.: +33 2 41 18 61 76; fax: +33 2 41 18 61 61. 2 Tel.: +33 2 41 76 60 22; fax: +33 2 41 76 22 12. are fed with maize silage from treated seeds (silage T). Data on fipronil excretion in milk are not available, but the metabolic pathway of fipronil in rats (urine and faeces), and data pertaining to the degradation of fipronil in soil are presented [5–6]. This information enabled us to select the fipronil metabolites and degradation products which were the most relevant to our study (Fig. 1). Considering the low systemic property of fipronil (K ow = 3.5) [7], very low levels of fipronil residues were expected in plants and milk (below 0.1 g kg -1 ). Few analytical methods for the determination of this compound and its residues have been reported. Morzycka [8] proposed a matrix solid-phase dispersion (MSPD) and gas chromatography nitrogen phosphorous detec- tor (GC-NPD) method for the determination of fipronil residues in honeybees. For animal tissues, methods with gas chromatog- raphy coupled to mass spectrometry (GC–MS) and electron capture detector (GC–ECD) [9] are proposed. The detection in soils can be conducted using solid-phase microextraction (SPME) GC–MS [10], GC–MS [11] and GC–ECD [11–13]. In plants, methods by GC–MS [9,11] and GC–ECD [11,13] 0039-9140/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2007.04.061