GB 23200.111-2018National food safety standard -- Determination of flumetsulam residues in plant-derived foods -- Liquid chromatography-mass spectrometry (English PDF)

1 Scope

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

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

2 Normative reference documents

The following documents are essential for the application of this document: For dated application documents, 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

Saflufenacil in the sample was extracted with acetonitrile, purified by dispersive solid-phase extraction, measured by liquid chromatography-mass spectrometry, and quantified by the external standard method:

4 Reagents and materials

Unless otherwise stated, only reagents confirmed to be of analytical grade and first-grade water complying with GB/T 6682 are used in the analysis:

4.1 Reagents

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

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

4.1.3 Anhydrous magnesium sulfate (MgSO4, CAS number: 7487-88-9):

4.1.4 Sodium chloride (NaCl, CAS number: 12125-02-9):

4.2 Solution preparation Formic acid solution (0:2 to 99:8, volume ratio): Accurately draw 1mL of formic acid and dilute it with water to 500mL, then place it in ultrasonic for 15 minutes and set aside:

4.3 Standard products Saflufenacil standard (C12H9F2N5O2S, CAS number: 98967-40-9): purity >=99.5%:

4.4 Preparation of standard solution

4.4.1 Saflufenacil standard stock solution (100 mg/L): Accurately weigh 10 mg (accurate to 0:1mg) saflufenacil standard in a 50mL beaker, dissolve it with acetonitrile and transfer 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 6 months:

4.4.2 Standard working solution of saflufenacil (10 mg/L): Accurately draw 1 mL of standard stock solution, add it to a 10 mL volumetric flask, dilute to volume with acetonitrile, and mix: Stored at 4°C, the validity period is 1 month:

4.5 Materials

4.5.1 N-propylethylenediamine (PSA): 40pm~60pm;

4.5.2 Graphitized carbon black (GCB): 120µm~400µm;

4.5.3 Octadecyl bonded silica gel (Cis): 50µm;

4.5.4 Florisil: 50µm:

4.5.5 Filter membrane: 0:22µm, organic system:

5 Instruments and equipment

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

5.2 Analytical balance:

5.3 Centrifuge,

5.4 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 or segments can be cut from different parts for processing; the sample should be chopped into small pieces, mixed thoroughly, and 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:

Vegetable oil samples were stirred evenly:

Samples should be stored at -18°C and below:

7 Analysis steps

7.1 Extraction

7.1.1 Vegetables, fruits, edible fungi, vegetable oils Weigh 10g (accurate to 0:01g) of the sample into a 50mL centrifuge tube, add 10mL acetonitrile, vortex and extract for 3 minutes; add 4g anhydrous magnesium sulfate and 1g sodium chloride to the centrifuge tube, vortex for 3 minutes; then Centrifuge at 4000r/min for 5 minutes, and the supernatant needs to be purified:

7.1.2 Cereals, oilseeds, nuts Weigh 5g (accurate to 0:01g) of the sample into a 50mL centrifuge tube, add 10mL of water into the centrifuge tube, and let stand for 15 minutes until the sample is completely wetted; then add 10mL of acetonitrile, vortex and extract for 3 minutes; centrifuge Add 4g anhydrous magnesium sulfate and 1g sodium chloride to the tube, vortex for 3 minutes; then centrifuge at 4000 r/min for 5 minutes, and the supernatant needs to be purified:

7.1.3 Tea and spices Weigh 2g (accurate to 0:01g) of the sample into a 50mL centrifuge tube, add 10mL of water into the centrifuge tube, and let stand for 15 minutes until the sample is completely wetted; then add 10mL of acetonitrile, vortex and extract for 3 minutes; centrifuge Add 4g anhydrous magnesium sulfate and 1g sodium chloride to the tube, vortex for 3 minutes; then centrifuge at 4000r/min for 5 minutes, and the supernatant needs to be purified:

7.2 Purification

7.2.1 Vegetables, fruits, edible fungi, grains, oils, tea Place 1:5mL of vegetable, fruit, edible fungi, grain, oil or tea sample supernatant into a 2mL centrifuge tube containing 30mg GCB and 150mg anhydrous magnesium sulfate, cover, vortex for 30 s, and centrifuge at 5000r/min After 5 minutes, take the supernatant and pass it through a 0:22µm filter membrane for testing:

7.2.2 Vegetable oils and nuts Put 1:5 mL of vegetable oil sample supernatant into a 2 mL centrifuge tube containing 50 mg of Florisil and 150 mg of anhydrous magnesium sulfate, cover it, vortex for 30 s, and centrifuge at 5000 r/min for 5 min: Take the supernatant and 0:22µm filter membrane, to be tested:

7.2.3 Spices

Put 1:5 mL of the supernatant into a 2 mL centrifuge tube containing 40 mg PSA, 10 mg GCB and 150 mg anhydrous magnesium sulfate: Cover the lid, vortex for 30 s, and centrifuge at 5000 r/min for 5 min: Take the supernatant and pass it through 0:22 µm filter membrane, to be tested:

7.3 Instrument reference conditions

7.3.1 Liquid Chromatography Reference Conditions

a) Chromatographic column: BEH Ci1:7µm (2:1mm×100mm) or equivalent;

b) Column temperature: 45°C;

c) Mobile phase: A is acetonitrile, B is formic acid solution (0.2%);

d) Injection volume: 5:0pL;

e) Flow rate: 0:3mL/min;

f) Mobile phase and gradient elution conditions: see Table 1:

7.3.2 Mass spectrometry reference conditions

a) Ion source type: ESI;

b) Capillary voltage: 3kV;

c) Cone gas: nitrogen, 50L/h;

d) Ion source temperature: 120°C;

e) Drying gas: nitrogen, flow rate 600L/h, temperature 350°C;

f) Collision gas: argon, 0:16mL/min;

g) Scanning method: positive ion scanning;

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

7.4 Preparation of standard working curve Accurately draw an appropriate amount of the series of standard solutions prepared in 4:4:2, dilute it with the matrix empty self-extracting solution, and prepare a mass concentration of 0:002mg/L, 0:01mg/L, 0:05mg/L, 0:1mg/L, 0:5mg/L, 1mg/L series matrix matching standard solutions for liquid chromatography-mass spectrometry measurement: Draw a standard working curve with the measured peak area as the ordinate and the corresponding standard solution mass concentration as the abscissa: Find the regression equation and determine the correlation coefficient: Matrix matching standard solutions should be prepared and used immediately:

7.5 Qualitative and quantitative determination

7.5.1 Retention time the retention time of the target compound chromatographic peak in the test sample is compared with the retention time of the corresponding standard chromatographic peak: The relative error should be within Within ±2.5%:

7.5.2 Quantitative ions, qualitative ions and product ion abundance ratios when measuring samples under the same experimental conditions, if the retention time of the detected chromatographic peak is consistent with that of the standard sample, and in the mass spectrum of the sample after subtracting the background, the mass spectrometric qualifier ion of the target compound should appear, and the same detection batch , for the same compound, if the relative abundance ratio of the two product ions of the target compound in the sample is compared with the standard solution of equivalent concentration, and the relative deviation does not exceed the range specified in Table 3, it can be judged that saflufenacil is present in the sample:

7.6 Determination

Inject the standard working solution and the solution to be tested into the liquid chromatography-mass spectrometer respectively, and use retention time and qualifier ions to determine the quality: The mass concentration of saflufenacil in the sample should be within the mass concentration range of the standard working curve and exceed the working curve: At the highest point, it should be diluted before analysis, and the external standard method should be used for quantification:

7.7 Blank test

Except that no sample is added, parallel operations shall be carried out according to the provisions of 7:1 to 7:6:

8 Result calculation

The residual amount of saflufenacil in the sample is measured by mass fraction, expressed in milligrams per kilogram (mg/kg), and calculated according to formula (1):

9 Precision

9.1 Under repeatability conditions, the absolute difference between the results of two independent measurements is not greater than the repeatability limit (r): The data for the repeatability limit (r) is:

a) When the content is 0:01mg/kg, the repeatability limit (r) is 0:004;

b) When the content is 0:05mg/kg, the repeatability limit (r) is 0:007;

c) When the content is 0:1mg/kg, the repeatability limit (r) is 0:016;

d) When the content is 0:5mg/kg, the repeatability limit (r) is 0:06;

e) When the content is 1mg/kg, the repeatability limit (r) is 0:069;

9.2 Under the conditions of reproducibility, the absolute difference between the results of two independent measurements is not greater than the reproducibility limit (R): The data of the reproducibility limit (R) is:

a) When the content is 0:01mg/kg, the reproducibility limit (R) is 0:005;

b) When the content is 0:05mg/kg, the reproducibility limit (R) is 0:043;

c) When the content is 0:1mg/kg, the reproducibility limit (R) is 0:051;

d) When the content is 0:5mg/kg, the reproducibility limit (R) is 0:043;

e) When the content is 1 mg/kg, the reproducibility limit (R) is 0:091:

10 Others

The method quantification limit of spices is 0:1mg/kg, and the method quantification limit of other samples is 0:01mg/kg:

11 Maps

The total ion chromatogram of the 0:1 mg/L saflufenacil standard solution is shown in Figure 1: