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This document specifies a gas chromatographic mass spectrometric (GC/MS) method for the determination of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in animal feeding stuffs and oil. The method is applicable to animal feeding stuffs consisting of less than 20 % by mass and oil/fatty samples containing residues of one or more of the following OCPs and PCBs and some of their isomers and degradation products: - aldrin; - dieldrin; - chlordane, as the sum of chlordane isomers and oxychlordane; - dichlorodiphenyltrichloroethane (DDT), as the sum of isomers op´-DDT, pp´-DDT, pp´-TDE (pp´-DDD), and pp´-DDE; - endosulfan, as the sum of a-/ß-isomers and endosulfan-sulphate; - endrin, as the sum of endrin and delta-keto-endrin; - heptachlor, as the sum of heptachlor and heptachlor epoxide; - hexachlorobenzene (HCB); - hexachlorocyclohexane isomers a-HCH (a-BHC), ß-HCH (ß-BHC), ?-HCH (?-BHC or lindane); - photo heptachlor; - cis- and trans-nonachlor; - non dioxin-like PCBs (ndl-PCBs), as the sum of PCB 28, 52, 101, 138, 153 and 180. The method has been fully validated by a collaborative trial for the substances and corresponding ranges (ng/g) noted in Table 1. The method has not been fully validated for oxychlordane, endrin ketone, cis- and trans-nonachlor and photo heptachlor in all matrices. The method is not applicable to chlorocamphene (toxaphene), a complex mixture of polychlorinated camphenes. Chlorocamphene has a very distinctive chromatographic profile and is easily recognisable by GC/ECD. Positive identification of the toxaphene isomers can be performed by negative chemical ionisation mass spectrometry (NCI-MS), electron impact tandem mass spectrometry (EI MS × MS) or electron impact high resolution mass spectrometry (EI-HRMS), which is not within the scope of this method. A limit of quantification (LOQ) for the mentioned organochlorine pesticides of 5 ng/g should normally be obtained. However, 10 ng/g applies for heptachlor aldrin, endrin, dieldrin, and endosulfan (a-, ß- and sulphate). For the ndl-PCBs an LOQ of 0,5 to 1,0 ng/g should be obtained. The LOQs mentioned apply to the individual compounds (i.e. not the sum of two or more compounds). Individual laboratories are responsible for ensuring that the equipment that they used will achieve these LOQs. On customers´ demand the standard may be applied to solely the analysis of PCBs or OCPs.