GB 23200.43-2016Food safety national standard -- Determination of residual chloroquine phosphate in grain and oilseeds -- Gas chromatographic method (English PDF)

4.1 Reagents

4.1.1 Acetone (C3H6O). Chromatographic pure.

4.1.2 Sodium bicarbonate (NaHCO3). Chromatographic purity.

4.1.3 Sodium hydroxide (NaOH).

4.1.4 dichloromethane (CH2Cl2). chromatographic purity.

4.1.5 Sulfuric acid (H2SO4).

4.1.6 anhydrous sodium sulfate (Na2SO4). 650 °C burning 4 h, set the dryer in the spare.

4.1.7 petroleum ether.

4.1.8 ether (C4H10O). re-distillation.

4.1.9 Potassium hydroxide (KOH).

4.2 Solution preparation

4.2.1 sulfuric acid solution. 3 mol/L.

4.2.2 Sodium hydroxide solution. 1 mol/L.

4.2.3 Potassium hydroxide solution. 10 mol/L.

4.2.4 Diazomethane. Set 4 mL of ether and 2 mL of potassium hydroxide solution in the reaction tube, add 5 mL of ether dissolved 2 g N-methyl-N-nitroso-4-toluenesulfonic acid amine solution, blowing nitrogen for 5 min, collecting the ether solution in the reaction tube.

4.3 Standards

4.3.1 Quinclorac acid standard. purity >= 99%.

4.4 Standard solution preparation

4.4.1 Quinclorac acid standard stock solution. accurately weighed the right amount of quinolinic acid standard, with a small amount of acetone dissolved, and petroleum ether Prepared as standard stock solution of 1 000 µg/mL, stored at 0 °C ~ 4 °C.

4.4.2 Quinclorac Acid Standard working solution. According to the work need to use petroleum ether diluted to the appropriate concentration of standard working solution.

4.5 Materials

4.5.1 Magnesium silicate solid phase extraction column. 6 mL/1 g, or equivalent.

6.1 Preparation of the sample

Take a representative sample 500 g, the sampling site according to GB 2763 Appendix A implementation, crushed with a pulverizer. Mix, are divided into two as a test Type, into a clean sample container, sealed and marked.

6.2 Sample storage

The sample was stored at -5 ° C.

During the operation of the sample preparation, the sample should be protected from contamination or changes in the content of the residue.

7.1 Extraction

Weigh 20 g (accurate to 0.01 g) sample in 250 mL stoppered conical flask, add 100 mL of acetone and shake for 30 min.

The filtrate was filtered into a 250 mL heart flask and the residue was washed twice with 50 mL of acetone. The washings were filtered and combined in the above-40 °C water bath evaporated to near dry, add 10 mL of water and 5 g sodium bicarbonate. After dissolving, add about 2 mL of sodium hydroxide solution, adjust the pH the value is 9 ± 0.2. Mixed thoroughly and moved into a separatory funnel, washed twice with 20 mL of water, and the solution was combined in a separatory funnel.

Add 100 mL of methylene chloride to the above-mentioned separatory funnel, shake for 5 min, allow to separate the layers, discard the lower organic phase, and then use 2 x 50 mL Dichloromethane repeatedly washed the water phase twice. About 5 mL of sulfuric acid solution was added to the aqueous phase to give a pH of 2 ± 0.2. Add 100 mL of dichloromethane and the mixture was allowed to stand for 5 min. The lower organic phase was separated from the Erlenmeyer flask and the aqueous phase was repeatedly extracted with 2 x 50 mL of dichloromethane Twice, combined with organic phase. Dehydrated by anhydrous sodium sulfate, placed in a heart-shaped bottle, in 40 °C water bath spin concentrated to near dry, adding 2 ML of acetone to dissolve the residue.

7.2 Derivatization

5 mL of diazomethane solution was added to the above acetone solution and sealed. The reaction was carried out in a water bath at 60 ° C for 10 min. The solvent was evaporated, Petroleum ether dissolved.

7.3 Purification

The magnesium silicate solid phase extraction column was installed on the solid phase extraction device, first with 6 mL of petroleum ether pre-leaching, discarded. The solution (7.2) was poured into to the solid phase extraction column, after all the outflow, and then 10 mL of petroleum ether in two separate solid phase extraction column, discarded. With 10 mL of acetone - stone Oil ether (9 1) to maintain the flow rate of 1.5 mL/min, collecting all the effluent, 45 °C nitrogen flow to near dry. Dissolved with petroleum ether and moved into a volumetric flask to a volume of 1.0 mL, measured by a gas chromatograph.

7.4 Derivatives of reference materials

Accurate removal of the appropriate concentration of quinacquine acid standard working solution in a heart-shaped bottle, in 40 °C water bath rotation concentrated to near dry, plus Into 2 mL of acetone to dissolve the residue, the following according to 7.2 operation.

7.5 Determination

7.5.1 Gas Chromatographic Reference Conditions

A) Column. BP10 quartz capillary column, 30 mx 0.25 mm (id), film thickness 0.25 m, or equivalent.

B) Column temperature. 240 ° C C) Inlet temperature. 280 ° C.

D) Detector temperature. 290 ° C.

E) Carrier gas. nitrogen, purity greater than or equal to 99.995%, 10 mL/min.

F) Injection volume. 1 µL.

G) Tail gas. nitrogen, purity greater than or equal to 99.995%, 50 mL/min.

7.5.2 Chromatographic determination

According to the content of pesticide in the sample solution, the standard working solution with similar concentration is selected. Standard working solution and methyl in the sample solution to be tested the response value of the pesticide should be within the linear range of the instrument detection. The standard working solution and sample solution were measured by volume injection. In the above Under the conditions of chromatography, the retention time of methyl quinclorac is about 3 min. The chromatogram of the standard is shown in Appendix A, Appendix A.1.

7.6 Blank experiment

In addition to the sample, according to the above determination steps.

10.1 Quantitation limits

The quantification limit of the method for quinclorac is 0.05 mg/kg.

10.2 Recovery rate

When the levels were 0.05 mg/kg, 0.5 mg/kg, 1.0 mg/kg, the recovery rates of the addition of quinclorac are shown in Appendix B.

Appendix A

(Informative)

Chromoquinoline methyl ester standard chromatogram

Table A.1 Gas chromatograms of methyl quinolinic acid methyl ester standards

Appendix B

(Informative)

Sample concentration and recovery of the experimental data

Table B.1 Experimental data on the concentration and recovery of the sample

sample name

Add concentration (mg/kg) 0.05 0.50 1.00 Brown rice 89.2% 87.9% 82.9% Corn 92.7% 91.3% 92.2% Wheat 88.2% 92.7% 88.2% Soybean 82.6% 83.1% 80.9% Appendix C (Normative appendix) Laboratory repeatability requirements

Table C.1 Laboratory repeatability requirements

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

Table D.1 Inter-laboratory reproducibility requirements

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