GB 23200.97-2016Food safety national standard -- Determination of 5 organophosphorus pesticide residues in honey -- Gas chromatographic method (English PDF)

4.1 Reagents

4.1.1 Ethyl acetate (C4H8O2). Chromatographic purity.

4.1.2 Sodium chloride (NaCl).

4.2 Standards

4.2.1 Organophosphorus standards. trichlorphon (CAS. 52-68-6), dolphin (fenchlorphos, CAS. 299-84-3), Chlorpyrifos, CAS. 2921-88-2, malathion, CAS. 121-75-5, coumaphos, CAS. 56-72-4) with a purity of & gt; 97%.

4.3 Standard solution preparation

4.3.1 trichlorfon, dolphin phosphorus, chlorpyrifos, malathion, fly poison phosphorus standard stock solution. were weighed the appropriate standard, respectively, with B the ethyl acetate was dissolved in a volume of 100 mL and the solution concentration was 100 µl/mL and stored in a 4 ° C refrigerator. Before use, dilute with ethyl acetate as needed to the appropriate concentration, as a mixed standard working fluid.

7.1 Extraction

Weigh 10 g homogeneous sample (accurate to 0.01 g), placed in 50 mL centrifuge tube, add 15 mL of water and 5 g of sodium chloride, mix, Then add 15 mL of ethyl acetate, mix on the mixer for 2 min, centrifuge 5 min (3 000 r/min), with a pointed nozzle to the upper layer of acetic acid the ethyl ester solution was transferred to a 100 mL concentrated flask and the aqueous phase was added to 15 mL of ethyl acetate. The above procedure was repeated and the extracts were combined twice.

The evaporator was concentrated in a water bath at 40 ° C under reduced pressure to near dryness, dissolved in 8 mL of ethyl acetate and quantitatively transferred to a 10 mL centrifuge tube.

The following water bath with a gentle nitrogen flow to dry, accurately add 1 mL of ethyl acetate, mix, gas chromatographic determination.

7.2 Determination

7.3.1 Gas Chromatographic Reference Conditions

A) Column. quartz capillary column, DB-1701, 30 mx 0.25 mm (inner diameter) x 0.25 m (film thickness), or equivalent;

B) Carrier gas. nitrogen (purity greater than 99.999%); carrier gas flow rate 1.0 mL/min; tail gas flow rate. 30 mL/min; hydrogen flow rate.

75 mL/min, air flow rate. 100 mL/min;

C) Column temperature. initial temperature 50 ° C for 2 min, rise to 180 ° C at 15 ° C/min for 1 min, rise to 290 ° C at 8 ° C/min Keep for 10 min;

D) Inlet temperature. 250 ° C;

E) Detector temperature. 250 ° C;

F) Injection method. no split injection;

G) Injection volume. 2 µL;

H) Opening time. 1.5 min.

7.3.2 Chromatographic determination

According to the content of organophosphorus pesticides in the sample, the standard working solution with similar peak area is selected. Standard working solution and sample solution the response value of organophosphorus should be within the linear range of the instrument. Standard working solution and sample volume and other volume interspersed injection determination. In the above chromatographic conditions the retention time of trichlorfon was about 6.0 min, the retention time of flocculent phosphorus was about 17.8 min, the retention time of chlorpyrifos was about 18.5 min, the retention time of malathion was about 18.9 min, and the retention time of flocculent phosphorus was about 27.8 min. The chromatogram of the standard is shown in Appendix A.

Figure A.1.

7.4 Blank experiment

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

10.1 Quantitation limits

The limit of quantification of organic phosphorus pesticides is 0.01 mg/kg.

10.2 Recovery rate

The recoveries of the experimental data (in the range of different additive concentrations) are as follows.

A) trichlorfon.

1) the concentration of 0.01 mg/kg in the recovery rate of 70-85%, precision 6.0%;

2) The concentration of 0.02 mg/kg was 70-90% and the precision was 9.2%.

3) The recovery of 0.1 mg/kg was 81-89% and the precision was 3.2%.

B) Flies phosphorus.

1) the concentration of 0.01 mg/kg in the recovery rate of 73-99%, the precision of 10.0%;

2) The concentration of 0.02 mg/kg was 75-95% and the precision was 7.7%.

3) the recovery of 0.1 mg/kg in the recovery rate of 80-97%, precision 6.4%;

C) chlorpyrifos.

1) the concentration of 0.01 mg/kg in the recovery rate of 84-102%, precision 6.3%;

2) the concentration of 0.02 mg/kg in the recovery rate of 80-100%, the precision of 6.7%;

3) The concentration of 0.1 mg/kg was 84-106% and the precision was 8.5%.

D) malathion

1) added at the concentration of 0.01 mg/kg recovery rate of 84-106%, precision of 7.6%;

2) The concentration of 0.02 mg/kg was 80-105% and the precision was 10.0%.

3) The recovery rate was 81-103% and the precision was 7.6% at 0.1 mg/kg.

E) flies poison phosphorus

1) the concentration of 0.01 mg/kg in the recovery rate of 74-96%, the precision of 10.0%;

2) The concentration of 0.02 mg/kg was 75-100% and the precision was 10.4%.

3) The concentration of 0.1 mg/kg was 80-102% and the precision was 7.9%.

Appendix A

(Informative)

Standard chromatogram

Figure A.1 Gas chromatograms of five organophosphorus standards

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