GB 23200.42-2016Food safety national standard -- Detection Method of Residual Fluoride in Grain (English PDF)

4.1 Reagents

4.1.1 Trichloromethane (CHCl3). Distillation.

4.1.2 anhydrous ether (C4H10O). re-distillation.

4.1.3 n-Hexane (C6H14). for pesticide residues analysis.

4.1.4 Acetone (C3H6O). re-distillation.

4.1.5 Dichloromethane (CH2Cl2). Distillation.

4.1.6 phosphoric acid (H3PO4).

4.1.7 Triethylamine (C6H15N).

4.1.8 Toluene (C7H8).

4.1.9 Hydrochloric acid (HCl).

4.1.10 anhydrous sodium sulfate (Na2SO4). anhydrous sodium sulfate at 650 °C for 4 hours, into the dryer standby.

4.2 Solution preparation

4.2.1 Phosphate solution. 1 g of sodium hydroxide and 17 g of disodium hydrogen phosphate, dissolved in water and diluted to 500 mL.

4.2.2 Pentafluorobromotoluene (PFBBr) Derivative Reagent. 100 µL Pentafluorobromotoluene was dissolved in 4.9 mL of toluene.

4.3 Standards

4.3.1 Fluprofen standard. content >= 99.5%.

4.4 Standard solution preparation

4.4.1 Fenfloxacin standard solution. accurately weighed the appropriate amount of Fenfen Wo Ling standard, with methanol dubbed 0.1mg/mL of the stock solution, according to Need to be diluted to the appropriate concentration of standard working fluid.

4.5 Materials

4.5.1 silica gel column. 3 mL, before use in the top of the column loaded 1c m high anhydrous sodium sulfate, and with two grams of methane-n-hexane (1585) Solution 3 mL pre-leaching.

5.10 Analysis of balance. 0.01 g and 0.0001 g

6.1 Preparation of the sample

The samples were scaled to 1 kg by quarter, all ground and passed through a 40 mesh sieve, mixed, divided into two portions, packed in clean containers Inside, sealed, marked mark. During sample and sample preparation, it is necessary to prevent contamination of the sample or the change in the content of the residue.

6.2 Sample storage

Keep the sample below 5 ° C in dark.

7.1 Extraction and purification

Weigh 0.5g homogeneous sample (accurate to 0.001g) in 15mL small test tube, add 2mL phosphoric acid and 1ml acetone, in the mixer quickly mixed 2 min, centrifuge 5 min (3000 r/min), with a tip of the straw to the phosphate - acetone extract into another tube, and then repeat the extraction of a Times the residue. Combined with phosphoric acid - acetone extract, add anhydrous sodium sulfate to saturation, with 3 × 2 mL of chloroform extraction, standing stratification, with the flask was transferred to another tube by adding a 2 mL of aqueous phosphate solution and rapidly mixed in a mixer for 2 min.

Centrifuge 5min (3000 r/min), separate the water phase, and then 2 × 2mL phosphate solution extracted chloroform twice, the water phase, with 1 . 1 hydrochloric acid water phase PH value of less than 2.0, adding excess anhydrous sodium sulfate to saturation, and then with 3 × 2 mL of anhydrous ether extraction of water, After the solution was allowed to stand, the anhydrous ether solution was transferred to a plug centrifuge tube by means of a pointed pipette in a multi-function micro-chemical sample processor or other Equivalent to 50 °C on the instrument through the nitrogen dry.

7.2 Derived

To a plug centrifuge tube containing the residue (7.1), add 100 µL of pentafluorobromotoluene derivative and 2 µl of triethylamine, in a multi-functional micro-chemical sample processor or other equivalent instrument at 90 °C for 1 hour, 50 °C with nitrogen blowing to near dry, add 1mL Dichloromethane-n-hexane (15 85) solution to dissolve the residue. Take the appropriate amount of standard working fluid in the multifunctional micro chemical sample processor or its He was equivalent to 50 °C on the instrument through the nitrogen dry, according to the same step child derived.

7.3 Silica gel column purification

The derivative of 7.2 was transferred to a silica gel column using 3 x 1 m L of dichloromethane-n-hexane (15 85), washed with 3 mL = Hexane (15.50) solution, discard the eluent and elute with 4 mL of methylene chloride and blown at 50 ° C Near dry, add 1.0 m L n-hexane volume, gas chromatographic analysis.

7.4 Determination

7.4.1 Chromatographic reference conditions

A) Column. HP-5 column, size. 30m × 0.32mm (inner diameter) × 0.25µm, or equivalent;

B) Column temperature. 100 ° C (1 min.) 30 ° C/min. 150 ° C (1 min.) 3 ° C/min.

C) Inlet temperature. 250 ° C;

D) Detector temperature. 280 ° C;

E) Carrier gas. nitrogen. purity >=99.999%, flow rate 3 mL/min, tail gas 30mL/min. ;

F) Injection method. no split injection;

J) Injection volume. 1 µL.

7.4.2 Chromatographic determination

According to the content of fenfluramine in the sample solution, the standard working solution with similar peak height is selected. Standard working solution and sample solution derived from fluorine the response value of pyridoxine should be within the linear range of the instrument. On the standard working solution and sample solution volume of the plug-in measurement, in the above chromatogram Conditions, the derivative of fluprofen after the retention time of about 28 min.

7.5 Blank test

In addition to the standard sample, according to the above measurement steps.

10.1 Quantitation limits

The limit of quantification of fluprofen was 0.02 mg/kg.

10.2 Recovery rate

When the concentration was 0.02 mg/kg ~ 1.0 mg/kg, the recovery was between 79% and 101%.

Appendix A

(Informative)

Fluoropitrazine standard derivatives Gas chromatograms Min 0 5 10 15 20 25 30 35 Hz ECD1 B, (HAX1129 \\ HAX11291.D) .9 Lo Fo Td

Figure A.1 Gas chromatogram of standard derivatives of fluproparine

Appendix B

(Normative appendix) Laboratory repeatability requirements

Table B.1 Laboratory repeatability requirements

Measured component content Mg/kg Precision <=0.001 36 > 0.01 > 1 14 Appendix C (Normative appendix) Inter-laboratory reproducibility requirements

Table C.1 Inter-laboratory reproducibility requirements

Measured component content Mg/kg Precision <=0.001 54 > 0.01 > 1 19