Animal feeding stuffs: Methods of sampling and analysis. Determination of OCPs and PCBs by GC/MS

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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 compound feeds and feed materials (oils and fats, fish meal).

The method is applicable to compound feeds consisting of less than 20 % water 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 o,p'-DDT, p,p'-DDT, p,p'-TDE (p,p'-DDD), and p,p'-DDE;
— endosulfan, as the sum of α-/β-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 α-HCH (α-BHC), β-HCH (β-BHC), γ-HCH (γ-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 (µg/kg) noted in Table 1.

Table 1 — Residue compound and range of (µg/kg) collaborative trial

Compound	Range (µg/kg)
all ndl-PCBs	0,7 to 39
aldrin	10 to 34
dieldrin	12 to 97
endrin	13 to 88
cis-chlordane^a	16 to 24^a
trans-chlordane	7 to 25
p,p’-DDT^b	19 to 200^b
o,p’-DDT	8 to 87
pp’-TDE^c	9 to 103^c
pp'-DDE	21 to 264
α-endosulfan	15 to 165
β-endosulfan	26 to 331
endosulfan sulphate^d	29 to 61^d
heptachlor	15 to 365
heptachlor epoxide	15 to 382
HCB^e	8 to 170^e
α-HCH	21 to 247
β-HCH	6 to 84
γ-HCH^f	17 to 186^f

NOTE The following information is to be taken into consideration:

a) Cis-chlordane has not been fully validated for chicken feed, pig feed and fish oil.
b) p,p’-DDT has not been fully validated for pig feed and vegetable oil.
c) pp’-TDE has not been fully validated for pig feed and fish meal.
d) Endosulfan sulphate has not been fully validated for pig feed and vegetable oil.
e) HCB has not been fully validated for fish oil.
f) γ-HCH has not been fully validated for fish oil.

The method has not been fully validated for oxychlordane, endrin ketone, cis- and trans-nonachlor and photo heptachlor in all matrices.

For those matrix-analyte combinations where the validation data were regarded insufficient, the results obtained with this method can only be regarded as screening results, unless the laboratory performs an in-house validation to show that satisfactory results can be obtained.

The method is not applicable to chlorocamphene (toxaphene), a complex mixture of polychlorinated camphenes. Chlorocamphene has a very distinctive chromatographic profile and is easily recognizable by GC/ECD. Positive identification of the toxaphene isomers can be performed by negative chemical ionization 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 6 to 29 µg/kg should normally be obtained (see Table 1). For the ndl-PCBs an LOQ of 0,5 to 1,0 µg/kg 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.