GB 23200.2-2016Food safety national standard -- Methods for the determination of herbicide residues -- Part 2: Determination of diphenyl ether herbicides in grain and oilseeds by gas chromatography-mass spectrometry (English PDF)

4.1 Reagents

4.1.1 Acetone (CH3COCH3). Chromatographic pure.

4.1.2 acetonitrile (CH3CN). excellent grade pure.

4.1.3 n-hexane (C6H14). chromatographic purity.

4.1.4 anhydrous sodium sulfate (Na2SO4). 650 °C burning 4 h, placed in the dryer in reserve.

4.2 Standards

4.2.1 Diphenyl Ether Herbicide Standards. See Appendix A.

4.3 Standard solution preparation

4.3.1 standard reserve solution. accurately weighed the right amount of benzoin ether, methylprednisolone ether, trifluoro-nitrofen, Lactobenzene, Herbicide, B Oxyfloxacin, Fluorofenoxylate, respectively, dissolved in acetone and fixed capacity to brown volumetric flask, the concentration is equivalent to 1 000 mg/L, stock solution storage Below -18 ° C.

4.3.2 mixed standard intermediate solution. accurate absorption of appropriate amount of benzoin, methylprednisolone, triflufen grass, lactoferrin, herbicidal ether, Ethoxifluorfen, Efloxacillin standard stock solution in brown volumetric flask, fixed with acetone to the scale, a variety of diphenyl ether herbicides concentrated the degree of 10 mg/L, the intermediate solution stored below -18 °C.

4.3.3 Mixed standard working solution. Mix the standard intermediate solution with acetone as needed and dilute it with other diphenyl ether herbicides and other concentrations of cyclodextrin and methoxylated ether, with nine kinds of diphenyl ether herbicides mixed standard working solution, mixed standard work the solution is stored at 0 to 4 ° C.

4.4 Materials

4.4.1 Florisil Solid Phase Extraction Column. 500 mg, 3 mL.

7.1 Extraction

Weigh 5 g (accurate to 0.01 g) sample in 50 mL centrifuge tube, add 2 mL of water and 20 mL of acetonitrile, then add 2 g of anhydrous sodium sulfate, Mixed in a vortex mixer for 3 min, centrifuged at 5000 r/min for 5 min, transferred to 10 mL of acetonitrile in the upper layer to another 15 mL centrifuge tube.

40 ° C water bath blowing nitrogen to dry, with n-hexane volume to 1 mL.

7.2 Purification

A 1 cm high anhydrous sodium sulphate was filled above the Fryborough Silica Solid Phase Extraction Column packing, pre-leached with 6 mL of acetone and 6 mL of n-hexane, respectively.

The extract was transferred to a solid phase extraction column, the column was discarded at a rate of 1 d/s, the effluent was discarded, and 5 mL of n-hexane-acetone (60 40, V/V) Followed by elution at a flow rate of 1 d/s. The eluate was collected in a 15 mL centrifuge tube and concentrated in a 40 ° C water bath to dryness, dissolved with n-hexane and Constant volume to 1.0 mL, gas chromatographic - mass spectrometry.

7.3 Determination

7.3.1 Gas Chromatography - Mass Spectrometry Reference Conditions

A) Column. HP-5MSI quartz capillary column. 30 m × 0.25 mm (inner diameter), film thickness 0.25 µm, or equivalent.

B) Column temperature. 70 ° C (2 min) 50 ° C/min 180 ° C 10 ° C/min.200 ° C 2 ° C/min 220 ° C 10 ° C/min 280 ° C (10 min).

C) Inlet temperature. 270 ° C.

D) Carrier gas. helium, purity greater than 99.999%, flow rate 1.0 mL/min.

E) Injection volume. 1 µL.

F) Injection method. no split injection, 1.5 min after the valve.

G) ion source temperature. 230 ° C.

H) Transmission line temperature. 280 ° C.

I) ionization mode. EI.

J) Ionization energy. 70 eV.

K) Monitoring mode. Select ion monitoring (SIM) and monitor ions See Appendix A.

L) solvent delay. 5 min.

7.3.2 Determination and confirmation of chromatography

According to the sample solution of diphenyl ether herbicide residue content, selected peak height similar to the standard working solution. Standard working solution and sample solution the residual response value of the diphenyl ether herbicide residue should be within the linear range of the instrument. The standard working solution and sample solution volume mixed injection Determination. If the sample solution is in the selective ion chromatogram of the standard working solution, a chromatographic peak appears at the same retention time, and the ion the abundance ratio is consistent with the relative abundance of the ions associated with the standard sample, and the similarity is within the tolerance (see Table 1), according to the selective ion Quantitative method. Under the above conditions of gas chromatography/mass spectrometry, cyproterone, trifluoroacetate, ethoxifen, herbicides, the retention times of oxygen herbicides, methylprednisolides, lactofenfen, and fenflufen are shown in Appendix A. 0.02mg/L mixed standard solution total separation Subflow Chromatogram See Appendix B, Figure B.1.

Table 1 Maximum allowable error for relative ion abundance using gas chromatography-mass spectrometry

7.4 Blank experiment

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

10.1 Quantitation limits

The quantification limit of this method was 0.025 mg/kg.

10.2 Recovery rate

When the levels were 0.025 mg/kg, 0.050 mg/kg, 0.100 mg/kg, the recoveries of diphenyl ether herbicides in rice and soybeans See Appendix C.

Appendix A

(Informative)

Diphenyl ether herbicide basic information, retention time and monitoring of ion abundance ratio

Table A.1 Basic information on the diphenyl ether herbicide, retention time and monitoring of the ion abundance ratio

Serial number

Pesticide Chinese

name

Pesticide English

name

CAS number Molecular formula Molecular retention time Min Monitor the ion abundance ratio

1 Cyclohexyl ether cinmethylin 87818-31-3 C18H26O2 270.40 10.041 105 * (100), 123 (44), 154 (15), 169 (16)

2 Trifluorobenzoate Fluorodifen 15457-05-3 C13H7F3N2O5 328.20 14.229 190 * (100), 126 (31), 162 (18), 309 (9), 328 (9) 3 oxyfluorfen 42874-03-3 C15H11ClF3NO4 361.70 15.177 252 * (100), 280 (16), 300 (31), 361 (38) 4 herbicides nitrofen 1836-75-5 C12H7Cl2NO3 284.09 15.680 283 * (100), 139 (27), 202 (49), 253 (18), 285 (77) 5 benzoate aclonifen 74070-46-5 C12H9ClN2O3 264.66 16.694 264 * (100), 77 (49), 183 (38), 194 (32), 212 (38)

6 Methoxy herbicides chlomethoxyfen 32861-85-1 C13H9Cl2NO4 314.12 19.584 313 * (100), 232 (36), 266 (79), 283 (33)

7 A Carboxylated Herbicide Bifenox 42576-02-3 C14H9Cl2NO5 342.13 20.404 341 * (100), 173 (18), 189 (17), 310 (26), 343 (71) 8 lactofen grass lactofen 77501-63-4 C19H15ClF3NO7 461.77 21.616 344 * (100), 207 (24), 223 (26), 346 (40)

9 Fluorofenoxylate

Fluoroglycofen-et

Hyl

77501-90-7 C18H13ClF3NO7 447.75 21.880 344 * (100), 207 (63), 223 (59), 315 (31) Note. "*" mark ions as quantitative ions Appendix B (Informative) Total ion chromatograms of nine kinds of diphenyl ether herbicides

Figure B.1 Diphenyl ether herbicide standard solution Total ion chromatogram

2. trifluoro-nitro-grass; 3. ethoxifen herb; 4. herbicidal ether; 5.

6. methoxylated herbicides; 7. methylprednisolide ether; 8. lactofen grass spirit; 9.

Appendix C

(Informative)

Addition recovery of diphenyl ether herbicides in rice and

Table C.1 Recovery of Diphenyl Ether Herbicides in Rice and Soybeans

No. Compound Name Sample Substrate Rice and soybeans

1 Cyclohexanone 72.0% ~ 100.0% 72.0% ~ 104.0%

2 Trifluorobenzoate 74.0% ~ 110.0% 70.0% ~ 108.0% 3 ethoxifluorfen 70.0% ~ 98.0% 70.0% ~ 106.0%

4 Herbicide 72.0% ~ 107.0% 70.0% ~ 106.0% 5 benzoate 72.0% ~ 105.0% 71.0% ~ 102.0%

6 Oxygen Herbicide 70.0% ~ 107.0% 72.0% ~ 96.0%

7 A Carboxylated Herbicide 72.0% ~ 107.0% 72.0% ~ 108.0%

8 Lactobenzene Cream 70.0% ~ 106.0% 71.0% ~ 104.0%

9 Fluorofenoxides 72.0% ~ 104.0% 70.0% ~ 104.0% Appendix D (Normative appendix) Laboratory repeatability requirements

Table D.1 Laboratory repeatability requirements

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

Table E.1 Inter-laboratory reproducibility requirements

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