GB 31656.10-2021National food safety standard - Determination of metaldehyde residues in aquatic products by liquid chromatography-tandem mass spectrometry method (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents" Drafting:

This document is published for the first time:

National food safety standards Determination of metaldehyde residues in aquatic products by liquid chromatography-tandem mass spectrometry

1 Scope

This document specifies the sample preparation and liquid chromatography-tandem mass spectrometry methods for detecting metaldehyde residues in aquatic products:

This document is applicable to the detection of metaldehyde residues in edible tissues of fish and shrimp:

2 Normative reference documents

The contents of the following documents constitute essential provisions of this document through normative citations in the text: Among them, the cited documents with dates are:

Only the version corresponding to the date applies to this document; for undated referenced documents, the latest version (including all amendments) applies to this document:

document:

GB/T 6682 Specifications and test methods for water used in analytical laboratories GB/T 30891-2014 Sampling specifications for aquatic products

3 Terms and definitions

There are no terms or definitions that need to be defined in this document:

4 Principles

The metaldehyde in the sample was extracted by acetonitrile homogenate, and the extract was salted out and purified using N-propylethylenediamine and C18 packing: The liquid chromatography G series Detection by mass spectrometry and quantification by internal standard method:

5 Reagents and materials

Unless otherwise specified, all reagents are of analytical grade and the water is first-grade water that complies with GB/T 6682:

5.1 Reagents

5.1.1 Acetonitrile (CH8CN): chromatographically pure:

5.1.2 Formic acid (HCOOH): chromatographically pure:

5.1.3 Sodium chloride (NaCl):

5.1.4 Anhydrous magnesium sulfate (MgSO,):

5.2 Preparation of solution 5:2:1 0.1% formic acid solution: Take 1mL of formic acid, add water to dissolve and dilute to 1000mL, and mix well:

5:2.250% acetonitrile solution: Pipette 100mL of acetonitrile, add 100mL of water, and shake well:

5.3 Standard products Metaldehyde and metaldehyde-D16 standard products, the content is >=95%, see Appendix A:

5.4 Preparation of standard solution

5.4.1 Standard stock solution (100 µg/mL): Take an appropriate amount of metaldehyde and metaldehyde-D16 (equivalent to 10 mg of active ingredient) and weigh them accurately:

Dissolve and dilute with acetonitrile respectively to a 100mL volumetric flask, shake well, and get it: Store below -18°C, valid for 6 months:

5.4.2 Standard intermediate solution (5:0µg/mL): Precisely measure 0:5mL each of metaldehyde and metaldehyde-D16 standard stock solution into 10mL respectively:

In a volumetric flask, dilute with acetonitrile to the mark, shake well, and get it: Store in a dark place at 2°C to 8°C, and is valid for 1 month:

5.4.3 Standard working solution (0:025 µg/mL): Precisely measure 0:5 mL of metaldehyde and metaldehyde-D16 standard intermediate solutions respectively:

In a 10mL volumetric flask, dilute to the mark with acetonitrile, shake well, and get it: Ready to use:

5.5 Materials

5.5.1 N-propylethylenediamine (PSA) filler, 40 mesh to 60 mesh or equivalent:

5.5.2 C filler, 40 mesh to 60 mesh or equivalent:

6 Instruments and equipment

6.1 Liquid chromatography-tandem mass spectrometer: equipped with automatic sampler and electrospray ion source:

6.2 Analytical balance: sensitive to 0:01g and 0:00001g:

6.3 Homogenizer,

6.4 Centrifuge tubes: polypropylene plastic centrifuge tubes, 10 mL and 50 mL:

6.5 Centrifuge: 10000 r/min or above:

6.6 Vortex mixer:

7 Preparation and preservation of samples

7.1 Preparation of samples Prepare samples according to the requirements of Appendix B of GB/T 30891-2014:

a) Take the homogenized test material as the test material;

b) Take the homogenized blank sample as the blank sample;

c) Take the homogenized blank sample, add the standard working solution of appropriate concentration, and add the sample as a blank:

7.2 Storage of samples Store below -18°C and conduct analysis and testing within 3 months:

8 Measurement steps

8.1 Extraction

Take 5 g of the sample (accurate to ±0:05 g), put it in a 50 mL centrifuge tube, add 100 µL of metaldehyde-Ds standard working solution (0:25 µg/mL), then add 2:0 mL of water and 10:0 mL of acetonitrile in sequence, and stir at 10000 r /min speed for 1 minute, add 2g of sodium chloride, cover and vortex for 1 minute, then centrifuge at 5000r/min for 2 minutes, collect the supernatant and set aside:

8.2 Purification

Take 2:0 mL of the reserve solution and transfer it into a 5 mL centrifuge tube containing 0:3 g of anhydrous magnesium sulfate, 0:1 g of Ci8, and 0:1 g of PSA: Vortex and mix for 1 min, centrifuge at 5000 r/min for 2 min, and draw 0:5 mL of the supernatant: Dilute the 0.1% formic acid solution to 1:0 mL, mix well, and pass through a 0:22 µm filter for liquid chromatography-tandem mass spectrometry measurement:

8.3 Preparation of standard curve Precisely measure appropriate amounts of 0:25 µg/mL metaldehyde standard working solution and 0:25 µg/mL metaldehyde-D1s standard working solution, and dilute with 50% acetonitrile solution to contain metaldehyde at a concentration of 0:05 µg/L, 0:10 µg/L, 0:25 µg/L, 0:50 µg/L, 1:0 µg/L, 2:5 µg/L and A series of standard solutions of 5:0 µg/L (internal standard concentrations are all 1:25 µg/L) for liquid chromatography-tandem mass spectrometry determination: Draw a standard curve with the concentration of the standard solution as the abscissa, the metaldehyde quantitative ion pair peak area and the metaldehyde-Ds ion pair peak area ratio as the ordinate: Find the regression equation and correlation coefficient:

8.4 Determination

8.4.1 Liquid Chromatography Reference Conditions

a) Chromatographic column: C18 column (50 mm×2:1 mm, 1:7µm) or equivalent;

b) Mobile phase: A is 0.1% formic acid solution, B is acetonitrile, and the gradient elution conditions are shown in Table 1;

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

d) Column temperature: 30°C;

e) Injection volume: 10µL:

8: 4: Determination method Take the sample solution and standard solution, conduct single-point or multi-point calibration, quantify by chromatographic peak area, and calculate by internal standard method: Standard solution and sample solution the characteristic ion mass chromatographic peak areas of the target drug should be within the linear range of instrument detection: The retention time of metaldehyde in the sample solution Compared with the metaldehyde retention time in the standard working solution, the deviation is within ±2.5%, and the relative ion abundance in the sample solution is consistent with the standard solution:

Compared with the relative ion abundance in the solution, it meets the requirements of Table 3: The multiple reaction monitoring chromatogram of the standard solution is shown in Appendix B:1:

8.5 Blank test

Take a blank sample and perform parallel operations using the same measurement steps except that no standard solution is added:

9 Calculation and presentation of results

The residual amount of the substance to be tested in the sample is calculated according to the standard curve or formula (1):

10 Sensitivity, accuracy and precision of detection methods

10.1 Sensitivity

The detection limit of this method in edible fish and shrimp tissues is 0:50 µg/kg, and the limit of quantification is 1:0 µg/kg:

10.2 Accuracy

The recovery rate of this method at the added concentration level of 1:0 µg/kg~2:0 µg/kg is 80%~120%:

10.3 Precision

The intra-batch relative standard deviation of this method is <=10%, and the inter-batch relative standard deviation is <=15%: