GB 23200.114-2018National food safety standard -- Determination of 208 pesticides and their metabolite residues in plant-derived foods -- Gas chromatography -- Mass spectrometry (English PDF)

1 Scope

This standard specifies a liquid chromatography-mass spectrometry method for the determination of blasticidin-S residues in plant-derived foods:

This standard is applicable to the determination of blasticidin pesticide residues in plant-derived foods:

2 Normative reference documents

The following documents are essential for the application of this document: For dated references, only the dated version applies to this document:

For undated referenced documents, the latest version (including all amendments) applies to this document:

GB 2763 National Food Safety Standard Maximum Residue Limits of Pesticides in Foods GB/T 6682 Analytical laboratory water specifications and test methods

3 Principles

The blasticidin in the sample was extracted with acetic acid aqueous solution, and after purification, it was detected by liquid chromatography-mass spectrometry and quantified by the external standard method:

4 Reagents and materials

Unless otherwise stated, only first-grade water confirmed as analytically pure reagents and in compliance with GB/T 6682 shall be used in the analysis:

4.1 Reagents

4.1.1 Acetic acid (CH3COOH, CAS number: 64-19-7); chromatographically pure:

4.1.2 Acetonitrile (CH3CN, CAS number: 75-05-8): chromatographically pure:

4.1.3 Formic acid (HCOOH, CAS number: 64-18-6): chromatographically pure:

4.1.4 Ammonium formate (HCOONH2, CAS number: 540-69-2):

4.1.5 Methanol (CH3OH, CAS number: 67-56-1): chromatographically pure:

4.2 Solution preparation

4.2.1 Acetonitrile solution (10 90, volume ratio): Add 100 mL acetonitrile to 900 mL water and mix well:

4.2.2 Acetic acid-acetonitrile-water solution (2 10 88, volume ratio): Add 2 mL acetic acid and 10 mL acetonitrile to 88 mL water and mix well:

4.2.3 Formic acid-methanol solution (10 90, volume ratio): Add 100mL formic acid to 900mL methanol and mix well:

4:2:420mmoL/L ammonium formate aqueous solution (pH=3:5): Weigh 0:385g ammonium acetate and dissolve it in an appropriate amount of water, and adjust the volume to 1000 mL, adjust pH to 3:5 with acetic acid:

4.3 Standard products Blasticide standard (C17H2sN8Os, CAS number: 2079-00-7): purity >=99.6%:

4.4 Preparation of standard solution

4.4.1 Standard stock solution (100mg/L): Accurately weigh 10mg (accurate to 0:1mg) of blasticide standard into a 50mL beaker, and use Dissolve the acetonitrile solution (4:2:1) and transfer it to a 100mL volumetric flask, dilute to volume with acetonitrile, mix well, and store in a freezer at -18°C away from light: The validity period is 3 months:

4.4.2 Standard working solution (10 mg/L): Take 1 mL of standard stock solution, add it to a 10 mL volumetric flask, dilute to volume with acetonitrile solution (4:2:1), and store in a freezer at -18°C away from light: The validity period is 1 month:

4.5 Materials

4.5.1 Solid phase extraction column: weak cation exchange solid phase extraction cartridge (500mg/6mL, weak cation exchange column with carboxyl functional group):

4.5.2 Filter membrane: 0:22µm, water system:

4.5.3 Octadecyl bonded silica gel (C): 40 µm ~ 60 µm:

5 Instruments and equipment

5.1 Liquid chromatography-tandem mass spectrometry: equipped with electrospray ion source (ESI):

5.2 Analytical balance: sensitivity 0:0001g and sensitivity 0:01g:

5.3 Tissue masher,

5.4 Centrifuge: the rotation speed is not less than 10000 r/min:

5.5 Rotary evaporator:

5.6 Vibration mixer (1200 times/min):

5.7 Vortex oscillator:

6 Sample preparation

Samples of vegetables, fruits and edible fungi should be taken in certain quantities in accordance with relevant standards, and the sampling locations should be in accordance with the provisions of GB 2763: For small individual samples, all are processed after sampling; for large individual and basically uniform samples, they can be divided or cut into small pieces on the axis or plane of symmetry and then processed; for slender, flat or component content in each part For samples with differences, small pieces can be cut from different parts or cut into small segments for processing; the sample should be chopped into small pieces, mixed thoroughly, sampled using the quartering method or directly put into a tissue masher and mashed into a homogenate: The homogenate was placed in a polyethylene container:

Take 500g of cereal samples, crush them so that they can all pass through a 425µm standard mesh sieve, and put them into polyethylene bottles or bags: Take 500g each of oil crops, tea leaves, nuts and spices samples, crush them and mix thoroughly, then put them into polyethylene bottles or bags:

Mix the vegetable oil evenly: Samples should be stored at temperatures below -18°C:

7 Analysis steps

7.1 Extraction

7.1.1 Cereals, tea, spices, nuts, vegetable oils Weigh 5g (accurate to 0:01g) of the sample into a 100mL centrifuge tube, refer to Appendix A to add water, and vortex for 2 minutes: Add 20 mL of acetic acid-acetonitrile-water solution (4:2:2), vortex for 2 minutes, oscillate and extract for 30 minutes, centrifuge at 8000 r/min for 10 minutes, pour out the supernatant, and add 20 mL of acetic acid-acetic acid to the centrifuge tube containing the residue: Repeat the above extraction step twice with acetonitrile-water solution (4:2:2), combine the supernatants, adjust the volume to 100 mL with the extraction solution, mix well, and wait for purification:

7.1.2 Fruits, vegetables and edible fungi Weigh 20g (accurate to 0:01g) sample into a 100mL centrifuge tube, add water according to the matrix moisture content listed in Appendix A, and vortex for 2 seconds min, add 20 mL of acetic acid-acetonitrile-water solution (4:2:2), vortex for 2 min, oscillate and extract for 30 min, and centrifuge at 8000 r/min for 10 min, pour out the supernatant, add 20 mL of acetic acid-acetonitrile-water solution (4:2:2) to the centrifuge tube containing the residue, repeat the above extraction steps twice, combine the extracts, adjust the volume to 100 mL with the extract, and mix: To be purified:

7.2 Purification

7.2.1 Cereals, tea, spices, nuts, and vegetable oils are purified with weak cation exchange solid-phase extraction cartridges: After the solid-phase extraction cartridges are activated with 5 mL of water and 5 mL of methanol, 20 mL of the extract solution is loaded onto the column, and 5 mL of each solid-phase extraction cartridge is used: Elute with water and 5 mL of methanol, drain the eluent, and finally elute with 10 mL of formic acid-methanol solution (4:2:3): Collect the eluate into a 50 mL pear-shaped bottle, spin and evaporate to dryness at 40°C, and use Dissolve the acetic acid-acetonitrile-water solution (4:2:2) and transfer it to a 5 mL volumetric flask, dilute the volume to 5 mL with the acetic acid-acetonitrile-water solution (4:2:2), and pass through a 0:22 µm microporous filter before testing:

7.2.2 Fruits, vegetables and edible fungi Pipette 5 mL from the extraction solution into a 10 mL centrifuge tube, add 100 mg of Ci8 powder, vortex for 3 minutes, centrifuge at 8000 r/min for 10 minutes, pass the supernatant through a 0:22 µm microporous filter, and wait Measurement:

7.3 Instrument reference conditions

7.3.1 Liquid Chromatography Reference Conditions

a) Chromatographic column: HILIC 100 mm×2:1mm (inner diameter), 1:7µm or equivalent;

b) Column temperature: room temperature;

c) Mobile phase: A is 20mmoL/L ammonium formate aqueous solution (pH=3:5), B is acetonitrile, the mobile phase and gradient elution conditions are shown in Table 1;

d) Flow rate: 0:25mL/min;

e) Injection volume: 10µL;

7.3.2 Mass spectrometry reference conditions

a) Ion source type: electrospray ion source;

b) Spray voltage: 2:8kV;

c) Capillary temperature: 550°C;

d) Atomizing gas flow: 600L/h;

e) Collision gas type: nitrogen;

f) Scanning method: positive ion scanning;

g) Detection method: multiple reaction monitoring (MRM), monitoring conditions are shown in Table 2:

7.4 Preparation of matrix standard working curve Prepare the blank matrix solution through 7:1 and 7:2, and dilute the standard intermediate solution to a mass concentration of 0:01 µg/mL, 0:02 pg/mL, 0:05µg/mL, 0:1µg/mL and 0:2µg/mL series of matrix standard solutions: The matrix standard solutions should be prepared and used immediately: Using the measured peak area as the ordinate and the corresponding standard solution mass concentration as the abscissa, draw a standard curve and find the regression equation and correlation coefficient:

7.5 Qualitative and quantitative

7.5.1 Retention time