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Annex 2 Food dimethyl fumarate residues (GC) 1 Scope This method provides food residues of dimethyl fumarate GC method. This method is suitable for food, pastries, fruits and other foods dimethyl fumarate residues. The detection limit (LOD) to: 25mg/kg, the minimum detectable concentration of 25ug/ml. 2 Normative references The terms of the following documents by the standard reference in the provisions of this standard. For dated references, subsequent to all of the amendments (excluding corrections) or revisions do not apply to this standard, however, encourage the parties to reach an agreement under this standard to explore the possibility to use the latest version of these documents . For undated reference documents, the latest versions apply to this standard. GB/T6682 analytical laboratory use specifications and test methods 3 Principles Samples of dimethyl fumarate (DMF) purified by extraction with attached hydrogen flame ionization detector gas chromatography for separation and determination, quantitative comparison with the standard series 4 Reagents and materials 4.1 Unless otherwise stated, all reagents were analytical pure. Water to meet the requirements of a water GB/T6682 4.2 chloroform 4.3 anhydrous sodium sulfate. 4.4 neutral alumina (chromatography with a 60-80 mesh). 4.5 standard solution stock solution: 0.1g of dimethyl fumarate (content 99.9%), with a small amount of chloroform dissolved, transfer to a 100ml volumetric flask, dilute with chloroform to the scale, the standard solution with fumaric Dimethyl 1mg/ml. 4.6 standard solution using the solution: standard solution 5,10,15,20,25,30 ml were drawn in the 100ml volumetric flask, dilute to the mark with chloroform, dimethyl fumarate concentrations were 50,100, 150,200,250,300 ug / ml. 5 instruments and equipment 5.1 gas chromatograph, with a flame ionization detector 5.2 Homogenize. 5.3 Grinder . 6 of the steps 6.1 Sample Preparation 6.1.1 food, pastries, and water containing solid foods like low fat Weighed 5.0g or 10.0g crushed samples, placed in 250ml conical flask with a plug, add 30ml of chloroform, shaking 30min, filtered with qualitative filter paper, take 10ml filtrate, blowing nitrogen to concentrate to 1ml, spare. 6.1.2 samples containing more fat Weighed crushed samples 10.0g, and neutral alumina 5-10g (depending on how much fat may be), the following in accordance with 6.1.1 "added 30ml of chloroform ..." since according to operator. 6.1.3 Fruits The fruit peel, cut into pieces, add distilled water in the machine homogenate homogenate, weighed 20.0g homogenate (equivalent to 10g samples), add chloroform 30ml, shaking 30min, with qualitative filter paper filter in 125ml separatory funnel, to be stratified, with anhydrous sodium sulfate filtered, the filtrate obtained 10ml, blowing nitrogen concentration to 1ml, tested. 6.2 Determination 6.2.1 Reference conditions for chromatography 6.2.1.1 Column: glass column (diameter 3mm, length 2m), built-coated with 2% OV-101 and 6% OV-210 60-80 mesh mixed stationary liquid ChromosorbW.AWDMCS (HP); 6.2.1.2 air flow rate: nitrogen 50ml/min; air 500ml/min; hydrogen 35ml/min;. 6.2.1.3 Temperature: gasification chamber and the detector 200 , the column temperature was 155 . . 6.2.1.4 Sample volume: 1 L. 6.2.2 Determination Into 1uL standard series in the concentration of the standard use of liquid in the gas chromatograph, the measured concentration of dimethyl fumarate peak height to concentration of horizontal, the corresponding peak value of the vertical axis, rendering the standard curve. At the same time injecting a certain volume of sample solution, the measured peak height with standard curve quantification. 6.2.3 Confirmation of positive samples In accordance with the above conditions and criteria for the work of test sample solution, if the quality of the sample in the chromatographic peak retention time consistent with the standard working solution (varied within the ± 2.5%) Conditions permit, by GC? MS qualitative 6.2.4 Blank test Not weighed, than outside, according to the above conditions and measured steps. 6.2.5 to allow poor Obtained in repeatability conditions, results of two independent determination of the absolute difference shall not exceed the arithmetic mean of 20%. 7 results calculated Samples of dimethyl fumarate residues calculated according to the following: X: samples of dimethyl fumarate residue, mg / kg A: Determination of Dimethyl Fumarate sample solution concentration, ug / ml V1: volume of concentrated extract with the sample, ml V2: samples of the total volume of chloroform extract, ml V3: concentrated sample volume, ml V4: standard solution volume, ul V5: sample solution, injection volume, ul M: sample weight, g 8 related technical parameters Method detection limit: 25mg/kg. Recovery 88.9% ~ 94.2% and the relative standard deviation of 4.32% ~ 9.07% of range. 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