GB 23200.41-2016Food safety national standard -- Method for the determination of thiaden residues in food (English PDF)

4.1 Reagents

4.1.1 Methanol (CH4O, 67-56-1). Chromatographic Purification.

4.1.2 n-hexane (C6H14,110-54-3). excellent grade pure.

4.1.3 Trichloromethane (CHCl3, 67-66-3). Chromatographic pure.

4.1.4 Acetone (C3H6O, 67-64-1). Chromatographic pure.

4.1.5 Sodium chloride (NaCl, 7647-14-5).

4.1.6 anhydrous sodium sulfate (Na2SO4,7757-82-6). before use at 650 °C for 4 h after burning, stored in a dryer, cooling standby use.

4.2 Solution preparation

4.2.1 Methanol - Aqueous solution (9 1, V/V). Accurately remove 90 mL of methanol and mix with 10 mL of water.

4.2.2 Acetone-Trichloromethane Solution (8 100, V/V). Accurately remove 8 mL of acetone and 100 mL of trichloromethane.

4.2.3 10% sodium chloride solution. accurately weighed 10 g sodium chloride in the beaker by adding the appropriate amount of water dissolved, transferred to 100 mL volumetric flask, set Capacity to scale, shake.

4.3 Standards

4.3.1 Thiaden standard (C6H10O4S2,55290-64-7). purity >=99%.

4.4 Standard solution preparation

4.4.1 Standard stock solution. accurately weighed 50 mg of thiophene pesticide standards (accurate to 0.1 mg) in 50 mL brown volumetric flask, with acetone Dissolved and constant volume to the scale, shake, the preparation of the concentration of 1000µg/mL standard stock solution, 0 °C ~ 4 °C dark preservation.

4.4.2 Standard Intermediate Solution. Accurately draw 1.0 mL of the standard stock solution in a 100 mL brown volumetric flask, dissolve with acetone and set the volume to the scale, the preparation of the concentration of 1 000 µg/mL standard intermediate solution, 0 °C ~ 4 °C dark preservation.

4.4.3 standard working solution. according to the need to remove a certain volume of the standard intermediate solution diluted to the appropriate concentration of standard working solution liquid. Standard working solution is ready for use.

4.5 Materials

4.5.1 Florisil Solid Phase Extraction Column. 500 mg, 3 mL, or equivalent.

4.5.2 Neutral Alumina Solid Phase Extraction Column. 500 mg, 3 mL, or equivalent.

6.1 Preparation of the sample

6.1.1 Fruits, vegetables and nuts

Take a representative sample 500 g, can not be washed with water after shredding, with a tissue crusher to sample processed into a slurry. Mix well and put it clean of the container, sealed and marked.

6.1.2 Tea and grain

Take a representative sample of 500 g, crushed with a pulverizer and passed through a 40 mesh sieve. Mix well, into a clean sample container, sealed and marked Mark.

6.1.3 Meat and meat products

Take a representative sample 500 g, cut it, and then use the tissue crusher to process the sample into a slurry, mix it, and mix it into a clean sample Inside, sealed and marked.

6.1.4 Honey and milk

Take a representative sample of 500 g, pour it into a clean enamel mix bucket, stir well and mix it into a clean container.

And mark the mark.

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

6.2 Sample storage

Tea, milk, honey, nuts and cereals and other samples at 0 °C ~ 4 °C preservation; fruit, vegetables, meat and meat products such as samples in the-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 Extraction

Weigh 2 g (accurate to 0.01 g) homogeneous sample in a 50 mL stoppered centrifuge tube, add 4 mL of water to mix for 15 min, add 5 mL Methanol - aqueous solution was placed on a vortex oscillator for 5 min, centrifuged for 4 min (centrifugal velocity 6 000 r/min), and the supernatant was collected in another 50 mL stoppered centrifuge tube, the residue was repeatedly extracted with 5 mL of methanol-water solution and the extracts were combined. Add 2 to the extract ML of sodium chloride solution and 5 mL of n-hexane for 2 min, centrifuged for 1 min (centrifugal speed of 5 000 r/min), and discarded and discarded the alkanes were extracted twice with 5 mL of n-hexane and the n-hexane layer was discarded. Add 5 mL of chloroform for 3 min, centrifuge 1 min (5 000 R/min), absorb the lower layer of chloroform in.200 mL chicken heart bottle, with 5 mL of chloroform and then extracted twice, combined extract, the extraction the solution was concentrated to about 1 mL in a 40 ° C water bath and purged.

7.2 Purification

A 1 cm high anhydrous sodium sulphate was added to the Florian silica solid phase extraction column and connected to the top of the neutral alumina solid phase extraction column, the tandem is mounted on a solid phase extraction device. Add 10 mL of acetone-chloroform solution before pre-leaching extraction column, discard the eluent, when the liquid level to reach the top of the anhydrous sodium sulfate, the sample obtained by the rapid extraction of 7.1 into the solid phase extraction column, with 2 mL of trichloride Methane Wash the heart of the chicken and repeat the washing three times. The whole wash solution was transferred to a solid phase extraction column and then washed with 15 mL of acetone-trichloromethane solution Elution and collection of all effluent in another.200 mL chicken heart flask, sprinkled in a 40 ° C water bath to near dryness, dissolved in acetone to 1.0 ML for GC-ECD determination and GC-MS confirmation.

7.3 Determination

7.3.1 Gas Chromatographic Reference Conditions

A) Column. HP-5 quartz capillary column, (30 mx0.32 mm (inner diameter) x 0.25 m), or equivalent.

B) heating process. the initial temperature of 50 °C, at 20 °C/min rate rose to 160 °C, keep 1 min, then 5 °C/min the rate rose to 230 ° C for 5 min.

C) Inlet temperature. 250 ° C.

D) Detector temperature. 300 ° C.

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

F) Tail gas. 25 mL/min.

G) Injection method. no split injection, 1.0 min after the opening valve.

H) Injection volume. 1 µL.

7.3.2 Gas Chromatography - Mass Spectrometry Reference Conditions

A) Column. HP-5MS quartz capillary column (30 m x 0.25 mm (inner diameter) x 0.25 µm), or equivalent.

B) column temperature. 100 °C for 1 min, at 5 °C/min rate rose to 160 °C for 1 min, then 20 °C/min the rate rose to 240 °C, keep 5 min.

C) Inlet temperature. 250 ° C.

D) chromatographic - mass spectrometer interface temperature. 280 ° C.

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

F) Injection volume. 1 µL.

G) Injection method. no split into the sample, 1 min after the valve.

H) ionization mode. negative chemical ion source (NCI).

I) Reactor. methane (40%), flow rate 2.0 mL/min ;.

J) Measurement method. Select the ion monitoring mode (SIM).

K) solvent delay time. 8 min.

7.3.3 Determination and confirmation of chromatography

According to the sample in the thiocyanate due to the content of pesticides, selected concentrations similar to the thiophene standard working solution. Standard working solution and sample solution the response value of the thiophene pesticide should be within the linear range of the instrument. On the standard working fluid and sample volume of alternating sampling to determine Retention time qualitative, measured sample solution and standard working fluid peak area compared to quantitative. Under the above gas chromatographic conditions, the thiophene is due to the standard color the spectrum is shown in Figure A.1.

When the sample is measured, if the retention time of the detected peaks is consistent with the standard sample, the mass spectrometry is confirmed. After deducting the background in the sample spectrum, the selected ions are present, and the selected ion abundance ratio is consistent with the ion abundance ratio of the standard sample (Allowable deviation range in Table 1), you can determine the presence of such pesticides or related chemicals in the sample. If you can not confirm, should re-injection, in the manner of scanning (with sufficient sensitivity) or by adding other confirmed ions or by using other analytical instruments of higher sensitivity.

Under the above gas chromatographic - mass spectrometry conditions, the monitoring ion (m/z) and the ion abundance ratio of the thiophene were 128. 210. 211. 212 = 32. 100. 11. 12, the total ion chromatogram and negative chemical ion spectrum (NCI) of the thiophene standard are shown in Figure B.1 and Figure C.1.

Table 1 Maximum allowable deviation of relative ion abundance when qualitative confirmation

Relative ion abundance /% > 50 > 20 ~ 50 > 10 ~ 20 <=10 Relative ion abundance Maximum permissible deviation /% ± 20 ± 25 ± 30 ± 50

7.4 Blank test

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

10.1 Quantitation limits

The quantification limit of this method is 0.01 mg/kg.

10.2 Recovery rate

When the levels were 0.01 mg/kg, 0.04 mg/kg, 0.1 mg/kg, the addition rate of the thiophene in the different substrates was increased See Appendix D.

Appendix A

(Informative)

Sulfate Pesticide Standard Gas Chromatography A.1 Thiophene Pesticide Standards Gas chromatograms are shown in Figure A.1

Figure A.1 Gas chromatographic chart of the thiophene pesticide standard (0.1 mg/kg)

Min0 5 10 15 20 25

ECD1 A, front signal (C. \\ CHEM32 \\ 1 \\ DATA \\ DIMETHIPHIN \\ 081209 \\ DIMETHIPHIN.2008-12-09 16-42-45 \\ SIG1000006.D) .6 .0 .6 4.

frequency/

Time/min

Appendix B

(Informative)

The total ion chromatogram of the thiophene pesticide standard B.1 The total ion chromatogram of the thiophene pesticide standard is shown in Figure B.1

Figure B.1 Total ion chromatogram of the thiophene pesticide standard (0.1 mg/kg)

Time/min

9 .0 01 0 .0 01 1 .0 01 2 .0 01 3 .0 01 4 .0 01 5 .0 01 6 .0 01 7 .0 01 8 .0 01 9 .0 02 0 .0 02 1. 0 02 2 .0 0 T ime - - > A bundance TIC. 0 8 1 2 1 5 0 0 5 .D \\ DATA .MS Ternary Abundance .2 Appendix C (Informative) Thiaden Pesticide Standard Quality Spectrum (NCI) C.1 Thiaden Pesticide Standard Quality Spectrum (NCI) See Figure C.1

Figure C.1 Ternary Pesticide Standard (0.1 mg/kg) Mass Spectrum (NCI)

Abundance

Mass ratio/m/z

Appendix D

(Informative)

The recovery rate of thiophene pesticide in different sample matrix

Table D.1 Recovery rates of thiophene pesticides in different sample matrices

Sample Substrate Add Concentration/(mg/kg) Recovery /% Sample Substrate Add Concentration/(mg/kg) Recovery /% Rice 0.01 80.2 87.5 Fish 0.01 97.3 109.1 0.04 80.1 94.5 0.04 88.7 107.9 0.10 85.7 94.3 0.10 90.8 106.8 Chinese cabbage 0.01 94.1 106.5 pork 0.01 93.7 101.5 0.04 83.7 106.7 0.04 84.0 96.0 0.10 96.4 104.7 0.10 90.8 106.9 Tangerine 0.01 99.3 105.8 beef 0.01 90.2 101.7 0.04 94.9 104.5 0.04 84.4 101.1 0.10 95.9 104.8 0.10 85.6 99.4 potato 0.01 97.1 109.1 Liver 0.01 93.2 111.3 0.04 88.6 108.9 0.04 83.7 104.5 0.10 96.3 110.6 0.10 87.7 105.2 tea 0.01 73.4 86.5 honey 0.01 92.8 107.8 0.04 77.1 88.1 0.04 91.5 99.9 0.10 77.2 90.2 0.10 95.1 108.1 Chestnut 0.01 81.2 90.2 egg 0.01 91.7 100.1 0.04 81.4 95.4 0.04 95.0 100.7 0.10 83.4 90.7 0.10 85.6 99.4 chicken 0.01 90.2 101.7 milk 0.01 97.8 108.5 0.04 82.3 98.0 0.04 99.6 109.0 0.10 86.297.1 0.10 90.8106.2 Appendix E (Normative appendix) Laboratory repeatability requirements

Table E.1 Laboratory repeatability requirements

Measured component content Mg/kg Precision <=0.001 36 > 0.01 > 1 14 Appendix F (Normative appendix) Inter-laboratory reproducibility requirements

Table F.1 Inter-laboratory reproducibility requirements

Measured component content Mg/kg Precision <=0.001 54 > 0.01