GB 23200.28-2016Food safety national standard -- Determination of residues of various herbicides in foodstuffs -- Gas chromatographic-mass spectrometry (English PDF)

4.1 Reagents

4.1.1 Acetonitrile (CH3CN). Chromatographically pure.

4.1.2 n-hexane (C6H14). pure chromatography.

4.1.3 Acetone (C3H6O). Chromatographic pure.

4.1.4 glacial acetic acid (C2H4O2).

4.1.5 anhydrous magnesium sulfate (MgSO4).

4.1.6 anhydrous sodium acetate (C2H3ONa).

4.2 Solution preparation

4.2.1 Extraction solvent (1% acetic acid in n-hexane saturated acetonitrile solution). add 10 mL of glacial acetic acid to 990 mL of acetonitrile (prior Saturated with n-hexane).

4.3 Standards

4.3.1 Reference material. Fluorodafen (CAS. 15457-05-3), Oxyfluorfen, CAS.

42874-03-3), herbicidal ether (Nitrofen, CAS. 1836-75-5), benzoyl ether (Aclonifen, CAS. 74070-46-5), piccon Lt;/RTI & (Ethoxyfen-ethyl, CAS. 131086-42-5), methicillin ether (Chlomethoxyfen, CAS. 32861-85-1), Ether (Bifenox, CAS. 42576-02-3), Lactofen (CAS. 77501-63-4) and Fenflufen (Fluoroglycofen-ethyl, CAS. 77501-90-7). purity >=98.0%.

4.4 Standard solution preparation

4.4.1 Pesticide standard stock solution. accurately weighed the appropriate amount of the standard, diluted with acetone prepared into 1.00 mg/mL single the standard stock solution is stored at 4 ° C (valid for 6 months).

4.4.2 mixed standard stock solution. respectively, the exact removal of the appropriate amount of the above standard stock solution, diluted with acetone prepared into 50 µg/mL mixture the standard stock solution is stored at 4 ° C (valid for 6 months).

4.4.3 mixed standard working solution. according to the need to use acetone diluted to the appropriate concentration of the standard working solution, stored at 4 °C (valid for 3 Month).

4.5 Materials

4.5.1 Graphitized carbon black filler. 40 µm.

4.5.2 PSA (N-2 aminoethyl) filler. 40 µm.

4.5.3 C18 Filler. 40 µm.

4.5.4 Microporous membrane. 0.45 µm, organic phase.

5.4 Tissue crusher

5.5 Crusher.

5.6 Homogenizer.

5.7 Oscillator.

6.1 Preparation of the sample

6.1.1 Spinach, green onions, peppers, strawberries and sweet peas

10 g of the sample was taken, and after shredding (without washing with water), the sample was processed into a slurry by a mashing machine. Mix, are divided into two as a sample, into the container, sealed and marked.

6.1.2 Green tea, rice and soybeans

500 g of the representative sample was taken, pulverized by a pulverizer and passed through a 2.0 mm round hole sieve. Mix well, into the container, sealed and marked.

6.1.3 Lobster, eel and pork

After picking 500 g of the sample, it was chopped, and the sample was successively crushed and mixed with a crusher, packed into a container, sealed and marked mark.

6.1.4 Honey

Take a representative sample volume of 500g, the crystallization of honey samples will be evenly stirred; on the crystallization of honey samples, in a closed situation Condition, the sample bottle placed in not more than 60 °C in the water bath in the warm, shaking, until the sample all melt and stir well, quickly cooled to room temperature, in the melt Must pay attention to prevent the evaporation of water. The prepared samples were divided into two separate sections, sealed into the vials, sealed and marked.

Note. The above sample sampling site according to GB 2763 Appendix A implementation.

6.2 Sample storage

Rice, soybeans, green tea, honey and other samples stored at 0 ~ 4 °C; spinach, green onions, peppers, strawberries, sweet peas, lobster, eel Fish and pork and other samples in -18 °C below the frozen storage.

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

7.1.1 Soybean, lobster, eel and pork and other samples

Weigh 5 g sample (accurate to 0.01 g).

7.1.2 Spinach, green onions, peppers, strawberries and sweet peas and other samples

Weigh 10 g sample (accurate to 0.01 g).

7.1.3 Rice, green tea and honey and other samples

Weigh 5 g of sample (accurate to 0.01 g) and add 4 mL of water, mix, soak or dissolve.

Tea to be soaked for 30 min.

7.2 Extraction

Place the weighed sample in a 250 mL stoppered conical flask, add 20 mL of the extraction solvent, add 15 g of anhydrous magnesium sulfate and 6 g of anhydrous vinegar Acid, the extraction of 40 min (beef, eel, lobster, chicken and other meat products should be homemade extraction 5 min), filtered in 150 mL concentrated bottle in. And then add 20 mL of extraction solvent to extract once again, the combined extract, 40 ° C spin concentrated to dry. The residue was dissolved in 2 mL of acetonitrile, to be purified.

7.3 Solid phase dispersion extraction purification

7.3.1 Spinach, green onions, peppers, strawberries, sweet peas and green tea extract

The corresponding sample extract of 7.2 was transferred to a small tube containing 50 mg of PSA filler and.200 mg of graphitized carbon black filler in advance.

Sub-vortex 1 min, until the pigment is completely eliminated, the filter membrane, gas chromatography-mass spectrometry and confirmation.

7.3.2 Rice, soybeans, lobster, eel, pork and honey extract

The corresponding sample extract of 7.2 was transferred to a solution containing 100 mg of PSA filler, 50 mg of graphitized carbon black filler and 100 mg of C18 filler in advance Tube, full vortex 1 min, filter membrane, gas chromatography - mass spectrometry determination and confirmation.

7.4 Determination

7.4.1 Gas Chromatography - Mass Spectrometry Reference Conditions

A) Column. DB-17ms quartz elastic capillary column, 30 m × 0.25 mm (id), film thickness 0.25 µm, or equivalent;

B) Column temperature. 90 °C 15 °C/min 270 °C 2 °C/min 276 °C 48 °C/min 300 °C (2.5 min);

C) Inlet temperature. 300 ° C;

D) chromatographic-mass spectrometer interface temperature. 250 ° C;

E) Carrier gas. helium, purity greater than or equal to 99.999%; flow rate, 1.0 mL/min;

F) Injection volume. 1 µL;

G) Injection method. splitless injection, 1.5 min after the opening valve;

H) ionization mode. NCI;

I) ionization energy. 184 eV;

J) ion source temperature. 150 ° C;

K) quadrupole temperature. 150 ° C;

L) Reaction gas. methane, purity greater than or equal 99.99%, reaction gas flow rate. 2 mL/min;

M) Detection mode. Select the ion monitoring mode (SIM), see Table 1;

N) solvent delay time. 5.5 min.

Table 1 Segment Select ion table

Pesticide retention time window (min) Retention time (min) Qualitative ion (m/z) Trifluorobenzoate 5.50-7.10 6.50 138 *, 190,298 Ethoxyphenanthrene ether 6.64 296,361 *, 363 Herbicide 6.83 283 *, 284,285 Benzoate 7.02 211 *, 228,264 Picolinate 7.11-7.85 7.26 349,376,412 * Quinoxaline 7.29 271 *, 272,273 Fluorinated Milk Ethers 7.64 378 *, 415,450 Oxygen herbicides 7.72 262,313 *, 315 Achaferrone 7.86-End 8.04 341 *, 342,343 Lactobacillus cerevisiae 8.66 461 *, 462,463 Fluorofenoxylate 8.68 294,447 *, 449 Note. The standard "*" is a quantitative ion.

7.4.2 Determination and confirmation of chromatography

According to the amount of pesticide residues in the sample solution, select the standard area similar to the standard working solution, the standard working fluid and sample volume Particle injection. The corresponding values of the pesticide to be tested in the standard working solution and the sample solution shall be within the linear range of the instrument.

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 after subtracting the background After the sample quality chromatogram, the selected ions are present, the abundance of the selected ions is higher than the abundance ratio of the corresponding ions of the standard.

Within the allowable range (see Table 2). According to quantitative ions (see Table 1 marked * debris) on its external standard quantitative. Diphenyl ether pesticide mix the total ion chromatogram of gas chromatography-mass spectrometry for standard solutions is shown in Figure A.1 in Appendix A.

Table 2 shows the maximum allowable error of relative ion abundance using gas chromatography-mass spectrometry

7.5 Blank experiment

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

10.1 Quantitation limits

The limit of quantification of 11 kinds of diphenyl ether pesticides in various substrates was 0.01 mg/kg.

10.2 Recovery rate

See Appendix C for the recovery range at the additional concentration levels in the different matrices.

As × m

Ax × Cs × Vx

Appendix A

(Informative)

Figure A.1 Alkaloid herbicide standard solution GC-MSD/NCI Select ion chromatogram

6.00 6.50 7.00 7.50 8.00 8.50 9.00 9.50 10.00 10.50 11.00 11.50 Tim e - > Abundance TIC. Diphenyl ether-std-3.D \\ data.ms

Figure A.1 Total ion chromatogram of GC-MS/NCI mixed standard solution of ether herbicide

Among them, 1 trifluoro-nitro-grass; 2 ethoxifluorfen; 3 herbicides; 4 phenylephrine; 5 piccones; 6 quinoxaline;

8 Methoxy herbicides; 9 A Carboxylated Herbicides; 10 Lacto Fen Grass; 11 Fluorofenoxides.

Appendix B

(Informative)

Molecular structural information of pesticides to be tested

1 Oxyfluorfen ethoxylate CAS Number. 42874-03-3 Molecular formula. C15H11ClF3NO4

2 Lactofen Lactoflavones CAS No.. 77501-63-4 Molecular formula. C19H15ClF3NO7 3 aclonifen CAS Number. 74070-46-5 Molecular formula. C12H9ClN2O3

4 Fluorodifen

CAS Number. 15457-05-3 Molecular formula. C13H7F3N2O5

5 Bifenox Methyl Carboxylate CAS Number. 42576-02-3 Molecular formula. C14H9Cl2NO5

6 Fluoroglycofen ethyl fluoride CAS No.. 77501-90-7 Molecular formula. C18H13ClF3NO7

7 Nitrofen Herbicide CAS Number. 1836-75-5 Molecular formula. C12H7Cl2NO3

8 Ethoxyfen ethyl fluoride CAS Number. 131086-42-5 Molecular formula. C19H15Cl2F3O5

9 Ethoxyfen

CAS. 188634-90-4

Molecular formula. C17H11Cl2F3O5

10 Chlomethoxyfen Methoxylated ether CAS Number. 32861-85-1 Molecular formula. C13H9Cl2NO4