Determination of diphenyl ether herbicide residues in grains and oilseeds by gas chromatography/mass spectrometry (1)

1 Scope

This part of SN/T 1737 specifies the cycloheptafen, methoxyfen, acloxyfen, carboxyfen, flulofenone, lactofen, fenflufen, ethoxyfluor in grains and oilseed.

This part applies to the detection and confirmation of 9 diphenyl ether herbicide residues in rice and soybean.

2 Method summary

The samples were extracted with acetonitrile, cleaned up with Florisil silica solid phase extraction column, determined by gas chromatography/mass spectrometer, and quantified by external standard metho.

3 Reagent materials

Unless otherwise stated, the reagents used are of analytical grade, and the water is first-grade wate.

1 Acetone: chromatographically pur.

2 Acetonitrile: excellent grade pur.

3 n-hexane: chromatographically pur.

4 Anhydrous sodium sulfate: calcined at 650℃ for 4h, and placed in a desiccator for later us.

5 Standard products of diphenyl ether herbicides: carboxyl ether (C ₁₄ H ₂₆ C1 ₂ NO ₅ , CAS No: 42576-02-3), flulotrizone (C ₁₃ H ₇ F ₃ N ₂ O ₅ , CAS No: 15457-05-3), herbicide (C ₁₂ H ₇ Cl ₂ NO ₃ , CAS No; 1836-75-5), Oxyfluorfen (C ₁₈ H ₁₃ ClF ₃ NO ₄ , CAS No: 42874-03-3), acifluorfen (C ₁₂ H ₉ Cl ₂ NO ₃ , CAS No: 74070-46-5), acifluorfen (C ₁₈ H ₁₃ ClF ₃ NO₇ , CAS No:, 77501-90-7), the purity is more than 90%; the purity of lactofapfop (C ₁₉ H ₁₅ ClF ₃ NO ₇ , CAS No: 77501-63-4) is more than 90.

6 Herbicide standard solution:

a) Standard stock solution: Accurately weigh an appropriate amount of acifluorfen, carboxyfluorfen, flulofenazone, lactofen, fenflufen, oxyfluorfen and carboxyfluorfen, and dissolve them in acetone respectivel.

b) Mixed standard intermediate solution: Accurately draw an appropriate amount of standard stock solutions of acifluorfen, carboxyfluorfen, flufenazone, lactofen, fenflufen, oxyfluorfen and carboxyfluorfen in a brown volume In the bottle, dilute to the mark with acetone, the concentration of various diphenyl ether herbicides is 10 mg/L, and this intermediate solution is stored below -18 ℃;

c) Mixed standard working solution: Dilute the mixed standard intermediate solution step by step with acetone as required, and add cyptofen and methoxydifenac with the same mass concentration as other diphenyl ether herbicides to prepare 9 kinds of diphenyl ethers Mixed standard working solution of ether herbicides, mixed standard working solution is stored at 0℃～4.

7 Florisil silica solid phase extraction cartridge: 500 mg, 3 m.

4 Instruments and equipment

1 Gas chromatography-mass spectrometer with electron bombardment sourc.

2 Vortex mixe.

3 Centrifuge.

4 Nitrogen blowing concentrato.

5 Solid phase extraction device

5 Sample preparation and storage

About 500 g of representative rice and soybean samples were taken, fully crushed, mixed well, put into a clean container, sealed and marked, and stored in a refrigerator at 4°.

6 Measurement steps

1 Extraction

Weigh 5g (accurate to 01g) of the sample into a 50ml centrifuge tube, add 2ml of water and 20ml of acetonitrile (2), then add 2g of anhydrous sodium sulfate (4), and mix on a vortex mixer 3 min, centrifuge at 5 000 r/min for 5 min, transfer the upper 10 mL of acetonitrile into another 15 mL centrifuge tube, blow nitrogen in a water bath at 40 °C until dry, and make up to 1 mL with n-hexan.

2 Purification

Fill 1 cm high anhydrous sodium sulfate above the packing of Florisil SPE column (7), and pre-rinse with 6 mL of acetone and 6 mL of n-hexane, respectivel.
The extract was transferred to a solid phase extraction column, passed through the column at a rate of 1 d/s, discarded the effluent, and eluted with 5 mL of n-hexane-acetone (60+10) at a flow rate of 1 d/.
The eluate was collected in a 15 mL centrifuge tube, concentrated to dryness with nitrogen blowing in a water bath at 40°C, dissolved in n-hexane and dilute to 1 mL for gas chromatography mass spectrometry determinatio.

3 Determination

1 Gas chromatography conditions

a) Chromatographic column: HP-5 MSI quartz capillary column: 30 m×25 mm (inner diameter), film thickness 25 um, or equivalent;

b) Column temperature

c) Injector temperature: 270℃;

d) Carrier gas: helium, purity greater than 9999%, flow rate 0 mL/min;

e) Injection volume: 1 uL;

f) Injection method: splitless injection, open the valve after 5 mi.

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