Available online at www.sciencedirect.com Talanta 75 (2008) 1320–1323 Low-temperature clean-up method for the determination of pyrethroids in milk using gas chromatography with electron capture detection Simone Machado Goulart, Maria Eliana L.R. de Queiroz ∗ , Ant ˆ onio Augusto Neves, Jos´ e Humberto de Queiroz Departamento de Qu´ ımica, Universidade Federal de Vi¸ cosa, Av. P. H. Rolfs, s/n, 36570-000 Vi¸ cosa-MG, Brazil Received 21 August 2007; received in revised form 22 January 2008; accepted 23 January 2008 Available online 8 February 2008 Abstract This paper describes a new gas-chrormatography with electron capture detection (GC-ECD) method for determination of some pyrethroids in milk samples. The extraction of the pyrethroids was carried out by liquid–liquid extraction with clean-up by precipitation at low temperature, without additional stages for removal of fat interferences. The method was efficient with recoveries of 93.0 ± 0.1% for cipermethrin and 84.0 ± 0.3% for deltamethrin. The quantification limits were 0.75 gL -1 for both pyrethroids. The method was simple, of easy execution, and used only small quantities of organic solvent. After optimization and validation, the method was used for the determination of residues of the pyrethroids cipermethrin and deltamethrin in milk and in lactea drink commercialized in Vic ¸osa (MG, Brazil). Some samples presented contamination with deltamethrin at levels below the maximum contamination limits established by the FAO. © 2008 Published by Elsevier B.V. Keywords: Pyrethroids; CG-ECD; Milk 1. Introduction The pyrethroids deltamethrin and cipermethrin are widely used in dairy farming to kill ticks. The contamination of milk by pyrethroids is caused by the application of these products on the body of the cows, in the cow barn, or even in the milk processing areas [1,2]. The contamination of milk is an extremely preoccu- pying factor, because milk is an essential food for human health and is widely consumed in the initial stages of life. Therefore, the determination of residues of pyrethroids in milk is essential to assure the quality of milk consumed as food. For the determination of pyrethroids in milk or other matrices, methods of extraction and quantification by chromatographic and electrophoretic techniques are normally used [3–9]. Nor- mally, the conventional techniques of pesticide extraction from milk, for quantification by gas chromatography, require large amounts of solvent and involve a large number of steps, mainly for the cleaning of extracts, often resulting in loss of analytes ∗ Corresponding author. Tel.: +55 31 3899 1430; fax: +55 31 3899 3065. E-mail address: meliana@ufv.br (M.E.L.R. de Queiroz). [10,11]. Moreover, the main difficulty for the determination of pyrethroids in both complex and fatty matrices, such as milk, is the co-extraction of fatty substances together with the pesti- cides [12], making quantification of residues of these pesticides in food impracticable. An alternative liquid–liquid extraction technique was devel- oped for extraction of organophosphorous insecticides in olive oil, in which the two phases are separated by freezing of the mixture. In this separation, the phase that contains the organic solvent and the pesticide residues remains liquid, whereas the other phase, composed mainly of the fatty matrix, is congealed. Insignificant amounts of fat materials are transferred to the liq- uid phase, so this technique does not require the use of additional stages for the purification of the extract [13]. The goal of the present work was the application of this new method for the extraction of deltamethrin and cipermethrin from milk, using gas-chrormatography with electron capture detection (GC-ECD). This method was based on liquid–liquid extraction followed by precipitation at low temperature. The method was used to evaluate the presence of pyrethroid residues in milk and in lactea drinks commercialized in Vicosa—MG, Brazil. 0039-9140/$ – see front matter © 2008 Published by Elsevier B.V. doi:10.1016/j.talanta.2008.01.058