GB 23200.82-2016Food safety national standard -- Determination of ethephon residues in meat and meat products (English PDF)

4.1 Reagents

4.1.1 Potassium hydroxide (KOH). Analytical purity.

4.1.2 Methanol (CH3OH). Distillation.

4.1.3 N-methyl-N-nitroso-p-toluenesulfonamide (C8H10N2O3S).

4.1.4 anhydrous ethanol (CH3CH2OH).

4.1.5 anhydrous ether. (C4H10O). re-distillation.

4.1.6 anhydrous sodium sulfate (Na2SO4). 650 °C burning 4 h, placed in a sealed container in reserve.

4.2 Solution preparation

4.2.1 Methanol - Hydrochloric acid (38%) solution (90 10).

4.2.2 Diazomethane solution. 10 ml of aqueous solution of potassium hydroxide (0.6 g/mL), 35 mL of ethanol and 10 mL of ether the double mouth distilled bottle is placed in a water bath on a magnetic stirrer heating plate. Place the stir bar in the bottle, connect the dropping funnel and the high-performance condenser, and condense it After the series, two 125 mL flasks were used as receiving bottles. 10 mL of ether was placed in the second flask and the inlet tube was inserted into the ether level the following. Place the two receiving bottles in an ice bath. The water bath was heated to 70 ° C while stirring with a magnetic stirrer and dropping from the dropping funnel A solution of N-methyl-N-nitroso-p-toluenesulfonamide in diethyl ether (21.5 g/140 mL) was added. The time to complete the total solution was controlled at 20 min , When the distillate was pale yellow, stop the distillation. The liquids in the two receiving bottles were combined as a diazomethane solution. If it contains impurities too can be re-distilled. The solution is stored in a refrigerator and stored for one month.

4.3 Standards

4.3.1 Ethephon standard. purity >= 99%

4.4 Standard solution preparation

4.4.1 ethephon standard solution. accurately weighed the right amount of ethephon standard, with methanol prepared into a concentration of 1.0 mg/mL standard reserve Liquid, dilute the standard stock solution with methanol to prepare the standard working solution at the appropriate concentration. Note. should be used when preparing standard solutions Polyethyleneware.

6.1 Extraction

Weigh about 20 g of sample (accurate to 0.1 g) in a polyethylene beaker by adding 0.5 mL of methanol-hydrochloric acid (90 10) solution and 40 mL of methanol, Extraction in an ultrasonic bath for 5 min. After centrifugation in a centrifuge tube (6000 r/min) for 2 min, the supernatant was aspirated with 100 mL of polyethylene in a polyethylene flask. The residue was again extracted with 40 mL of methanol as described above and the combined extracts were pooled in the same polyethylene flask.

6.2 Purification

The polyethylene flask containing the methanol extract was frozen in a freezer at -18 ° C for 4 h. Removed quickly after the transfer into the centrifuge tube Heart (6000 r/min) 5 min. The supernatant was poured into a 250 mL heart flask treated with dimethyldichlorosilane. The remaining residue was washed with 2 mL Frozen methanol washed, the lotion transferred to the same heart bottle. Concentrated to about 60 mL on a 30-35 & lt; 0 & gt; C water bath with a rotary evaporator. Will be thick the distillate was transferred to a 100 mL volumetric flask treated with dimethyldichlorosilane. Wash the flask with a small amount of methanol, the lotion into the volumetric flask.

With methanol volume.

6.3 Derivatization

10.0 mL of the above solution was taken, placed in a 15 mL stoppered centrifuge tube, and concentrated in a 30-35 ° C water bath under a dry nitrogen stream About 1.5 mL. Add 0.5 mL of methanol-hydrochloric acid solution (90 10) and 8 mL of anhydrous ether, mix well for 10 min. Will be the upper layer the solution was poured into another plug tube and the residue was washed with 2 x 1 mL of anhydrous ether. The lotion is incorporated into the above solution. Under nitrogen flow 30-35 ° C water bath to about 1 mL. In the fume hood, dropping the diazomethane solution into the concentrate until the yellow does not fade. Cover strict Stopper, placed for 15 min. The excess diazomethane was blown off with a nitrogen stream. And then washed with 2 × 5 mL water, each centrifugation (6000 r/min) 2 min, Discard the lower aqueous phase. Concentrate to about 0.8 mL in a 30-35 ° C water bath with a nitrogen stream and dilute to 1.00 mL with anhydrous ether. The solution is treated with about 0.5 g anhydrous sodium sulfate after dehydration gas chromatographic determination.

6.4 Derivation of standard solutions

Take the appropriate amount of ethephon standard working solution, placed in a 100 mL stoppered polyethylene flask, add diazomethane solution until yellow does not fade until. Cover the stopper and place it for 15 min. The excess diazomethane was blown off with a nitrogen stream, and the solution became colorless. The flask was placed at 30-35 ° C the water bath was concentrated to near dryness under a nitrogen stream and the residue was dissolved in anhydrous ether and diluted to the same volume of the standard working solution.

6.5 Determination

6.5.1 Gas Chromatographic Reference Conditions

A) Column. stainless steel column, 2m × 3 mm (inner diameter), filler 3% (m/m) FFAP applied to Chromosorb G, AW, DMCS (60-80 mesh);

B) Carrier gas. nitrogen, purity >= 99.9%, 50 mL/min C) Hydrogen. 4 mL/min ;.

D) Air. 175 mL/min

E) Column temperature. 145 ° C F) Inlet temperature. 230 ° C G) Detector temperature. 300 ° C H) Injection volume. 1 µL

6.5.2 Chromatographic determination and confirmation

According to the sample measured pesticide content, selected peak height similar to the standard working solution, the standard working solution and the sample solution of pesticides the response value of the derivative should be within the linear range of the instrument detection. The standard solution and the sample solution should be equal to the volume of the sample injection. In the above color Under the conditions of the spectrum, the retention time of the ethephon derivative (dimethyl ethenanthrene) was about 1.6 min. The chromatograms of the standard derivatives are shown in Appendix A.

Figure A1.

6.6 Blank experiment

Unless the sample is not weighed, according to the above measurement steps.

9.1 Limit of limits

The limit of gelatinization of this method is 0.01 mg/kg.

9.2 Recovery

When the addition level was 0.01 mg/kg, 0.1 mg/kg, 1 mg/kg, the recovery rate of ethephon was 84.6-90.2%.

23200.82-2016

Appendix A

(Suggested appendix) Standard chromatogram

Figure A1 Derivatives of ethephon standard (dimethyl ethenanthrene) Gas chromatogram

23200.82-2016

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 23200.82-2016 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