GB 23200.29-2016Food safety national standard -- Determination of residual residues of oxazabs in fruits and vegetables by liquid chromatography (English PDF)

4.1 Reagents

4.1.1 Methanol (CH3OH). Chromatographic Purification.

4.1.2 n-hexane (C6H14). pure chromatography.

4.1.3 Ethyl acetate (C4H8O2). Chromatographic purity.

4.1.4 Anhydrous sodium sulfate (Na2SO4). 650

C burning 4 h, in the dryer to cool to room temperature, stored in a sealed bottle in reserve.

4.2 Solution preparation

4.2.1 sodium chloride solution (10%). take 10 g of sodium chloride, the volume of water to 100 mL, shake back.

4.3 Standards

4.3.1 Streptomide standard (Fenpyroximate, CAS.NO .. 111812-58-9). purity >=99%.

4.4 Standard solution preparation

4.4.1 Streptomide standard stock solution. accurately weighed appropriate amount of azole mite ester standard, with acetonitrile prepared into a concentration of 100 µg/mL standard reserve liquid. According to the need to use acetonitrile diluted to the appropriate concentration of standard working fluid.

4.5 Materials

4.5.1 Neutral alumina solid phase extraction column. 1 000 mg, 3 mL.

6.1 Preparation of the sample

To replace the sample of about 500 g, the sampling site according to GB 2763 Appendix A, the individual large samples need to be chopped, into the high-speed organization the crusher is mashed evenly, packed in a clean container, sealed and marked with a mark.

6.2 Sample storage

Samples were stored at 0 - 4 ° C. During the operation of the sample preparation, it is necessary to prevent contamination of the sample or change in the content of the residue.

7.1 Extraction

Weigh 15 g (accurate to 0.01 g) sample placed in 50 mL centrifuge tube, add 20 mL of methanol, high-speed homogenization 2 min. 4000 r/min Centrifuge 4 min, filter, add 20 mL of methanol residue, vortex 1 min, repeat centrifugal filtration operation, combined filtrate, to be purified.

7.2 Purification

The filtrate was transferred to a 250 mL separatory funnel, 40 mL of sodium chloride solution and 20 mL of n-hexane were added, vigorously shaken for 2 min, the layers were placed in a 100 mL stoppered flask. The aqueous layer was repeatedly extracted with 20 mL of n-hexane and the n-hexane layer was combined.

Add 2 g of anhydrous sodium sulfate, shake, after standing, the n-hexane layer into the 100 mL concentrated bottle, and then a small amount of n-hexane washing with a plug cone the bottles are washed twice and the washings are combined to the vials. In 40 ° C water bath rotation concentrated to near dry.

The flask was washed with 3 x 3 mL of n-hexane-ethyl acetate (28) and the solution was transferred to 5 mL of ethyl acetate pre-leached neutral oxygen in the aluminum solid phase extraction column, the flow rate was controlled by about 2 mL/min, and the whole effluent was collected. Dried in a nitrogen bath at 40 ° C and dissolved in the mobile phase Constant volume to 1.0 mL, over 0.45 µm filter for liquid chromatography analysis.

7.3 Determination

7.3.1 High Performance Liquid Chromatography Reference Conditions

A) Column. ZORBAX SB-C18,5 µm, 250 mm × 4.6 mm (id) or equivalent;

B) Mobile phase. acetonitrile - water (85 15).

C) Flow rate. 0.8 mL/min.

D) Detection wavelength. 254 nm.

E) Injection volume. 40 µL.

7.3.2 Determination and confirmation of chromatography

According to the test solution of azole mite content of the situation, selected peak area similar to the standard working solution. Standard working solution and sample solution of oxazolamate the response value should be within the linear range of the instrument detection. Standard working solution and sample volume and other volume interspersed injection determination. Under the above chromatographic conditions, the reference retention time of the azole was 9.8 min. The liquid chromatogram of the standard solution of the azole compound is shown in Figure A.1 in Appendix A.

7.4 Blank experiment

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

10.1 Quantitation limits

The limit of this method is 0.02 mg/kg.

10.2 Recovery rate

10.2.1 Additive concentration and recovery of azoxystrobin in citrus experimental data.

The recoveries were 80.4% ~ 97.5% at the concentration of 0.02 mg/kg.

The recoveries were 83.5% ~ 97.1% at the concentration of 0.05 mg/kg.

When the concentration of azole was increased at 0.20 mg/kg, the recovery was 87.8% ~ 101.7%.

10.2.2 Chinese cabbage mites added concentration and recovery of experimental data.

The recoveries were 78.2% ~ 96.0% at the concentration of 0.02 mg/kg.

The recoveries were 81.7% ~ 97.4% at the concentration of 0.05 mg/kg.

The recoveries were 87.3% ~ 102.5% at the concentration of 0.20 mg/kg.

Appendix A

(Informative)

Standard chromatogram

Figure A.1 Schematic diagram of azolecarboxide standard liquid chromatography

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