GB 23200.26-2016Food safety national standard -- Detection Method of 9 Kinds of Organic Heterocyclic Pesticide Residues in Tea (English PDF)

3.1 Reagents

3.1.1 Acetone (CH3COCH3). Distillation.

3.1.2 n-hexane (C6H14). re-distillation.

3.1.3 Sodium chloride (NaCl).

3.2 Solution preparation

3.2.1 Acetone-n-Hexane (1 3) Solution. Take 100 mL of acetone, add 300 mL of n-hexane and shake well.

3.2.2 Acetone - n-Hexane (2 1) Solution. Take.200 mL of acetone, add 100 mL of n-hexane and shake well.

3.3 Standards

3.3.1 Pesticide standards. purity >= 99%.

3.4 Standard solution preparation

3.4.1 standard solution. accurately weighed amount of atrazine, vinblastin, pyrithione, fluconazole, imazalazole, buprofezin, Propiconazole, chlorophenyl pyrimidol, pyridaben standard, with acetone prepared into a concentration of 1.00 mg/mL standard stock solution. And then according to Need to use n-hexane diluted to the corresponding standard working fluid.

3.5 Material

3.5.1 anhydrous sodium sulfate (Na2SO4). after 650 °C burning 4h, placed in the dryer in reserve.

3.5.2 Activated Carbon Solid Phase Extraction Column. 250 mg or equivalent.

3.5.3 Neutral alumina solid phase extraction cartridge. 250mg or equivalent.

5.1 Preparation of the sample

The recovered sample is ground and the sampling site is carried out according to GB 2763 Appendix A, passing through a 0.84 mm Uniform, are divided into two, into a clean container, as a sample. Sealed and marked with mark.

5.2 Sample storage

Keep the sample below 5 ° C in dark. During sampling and sample preparation, it is necessary to prevent contamination of the sample the change in residue content occurs.

6.1 Extraction

Accurately weigh 1 g homogeneous sample (accurate to 0.001g) in a 15 ml centrifuge tube, add 1 g of sodium chloride, add 2 mL of steam Water, mix on the mixer for 30 s, place it for 30 min, add 4 mL of acetone and n-hexane mixture, mix well on the mixer 2 min. Centrifuge at 2 500 r/min for 1 min and draw the upper n-hexane extract in another 15 mL graduated tube. And then points Do not add 2 mL of acetone and n-hexane mixture to extract twice, the combined extract, add 1 g anhydrous sodium sulfate to dry. will the dried extract was completely transferred to another clean scale tube placed on a microtiter sample processor at 50 ° C, to about 1 mL (solution A).

6.2 Purification

The activated carbon solid phase extraction column and neutral alumina solid phase extraction column (activated carbon solid phase extraction column filled about 1cm high of the anhydrous sodium sulfate layer) from top to bottom installed in the solid-phase extraction of the vacuum filter device, first with 1 mL × 3 acetone pre-leaching small Column, and then 1 mL x 3 n-hexane pre-leaching column, keep the drip rate of 0.5 mL/min, discard all eluent.

The solution A was subjected to a solid-phase extraction solid column and a neutral alumina solid phase extraction column, followed by 6.0 mL of acetone and the mixture was eluted and the whole eluent was collected and placed at 50 ° C and the nitrogen stream was blown to near dryness. Finally, with n-hexane 0.5 mL for GC-MSD analysis.

6.3 Determination

6.3.1 Gas Chromatography - Mass Spectrometry Reference Conditions

A) Column. quartz capillary column, 5% phenylmethylpolysiloxane stationary phase. 30 m x 0.20 mm (inner diameter), film thickness 0.25µm, or equivalent;

B) Column temperature. 70 ° C for 2 min, rise to 180 ° C at 8 ° C/min, rise to 280 ° C at 3 ° C/min, Keep for 18 min;

C) Inlet temperature. 250 ° C;

D) chromatographic - mass spectrometer interface temperature. 220 ° C;

E) Carrier gas. helium (purity > 99.995%), 0.6 mL/min;

F) Injection volume. 1 µL;

G) Injection method. no split injection, 1 min after the opening valve;

H) ionization mode. EI;

I) ionization energy. 70 ev;

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

K) monitoring ions (m/z). see Table 2;

I) solvent delay. 15 min.

Table 2 9 Monitoring of heterocyclic pesticides in ions

Pesticide collection time/min Monitoring ions (m/z) Atrazine 15 to 20 173, 187,.200a), 215 Vibrio Bacteria 20 ~ 25 187,198,212 a), 285 Pythium 25 ~ 26.5 96a), 255,283,285 Fenfluazole 25 to 26.5 219, 248, 278a), 287 Oxytocin 26.5 to 28.2 173 a), 215, 240, 296 Buprofezin 28.2 ~ 30.5 105a), 172,175,305 Propiconazole 30.5 to 36 173a) .191.259.261 Chlorophenyl pyruvate 36-40.5 139a), 219,251,330 Pyridenopsis 40.5 ~ 43 117,147a), 309,364 A) the labeled ions are quantitative ions

6.3.2 Chromatographic determination

According to the sample in the atrazine, vinblastide, pyrithione, fluconazole, imazalazole, buprofezin, propiconazole, chlorobenzene Pyrimethanol, pyridaben content of the situation, selected peak area similar to the standard working solution. Standard working solution and sample solution Thiocarbamate, pyrithione, chlorpheniramine, imidazole, buprofezin, propiconazole, chlorophenyl pyruvate, the values shall be within the linear range of the instrument detection. The sample solution of the standard working fluid was measured by volume injection. In the above chromatogram Conditions, the standard SIM chromatogram is shown in Appendix A, Figure A.1.

6.3.3 Confirmation of mass spectrometry

The standard solution and sample solution were determined according to the conditions specified in 4.4.3.1, if the same solution in the sample solution with the standard Leaving time there is a peak, then its mass spectrometry confirmed. When the relative abundance of the monitored ions is consistent with the standard, and the similarity is plus or minus 10%, can confirm the test object. Under the above gas chromatographic - mass spectrometric conditions, nine heterocyclic pesticides the retention time and the monitoring ion abundance ratio (m/z) are shown in Table 3.

Table 3 9 kinds of heterocyclic pesticide retention time and monitoring of ion abundance ratio

Pesticide retention time/min Monitoring ion abundance ratio Atrazine 18.41 173. 187..200. 215 (26. 3. 100. 58) Velvetlein 21.09 187. 198. 212. 285 (74. 89. 100. 86) Phytophthora 25.46 96. 255. 283. 285 (100. 8. 69. 5) Fluorobenzene 25.67 219. 248. 278. 287 (18. 7. 100. 53) Antimoxazole 27.33 173. 215. 240. 296 (76. 100. 9. 6) Buprofezin 28.30 105. 172. 175. 305 (100. 35. 25. 6) Propiconazole 32.20,32.58 173. 191. 259. 261 (100. 27. 88. 57) Chlorophenylpyrimidol 39.12 139. 219. 251. 330 (100. 63. 54. 36) Pyridinone 41.64 117. 147. 309. 364 (15. 100. 7. 6)

6.4 Blank experiment

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

9.1 Limit of limits

The limiting limit of the method for atrazine is 0.02 mg/kg, the volatilization limit for vinifera is 0.02 mg/kg, is 0.02 mg/kg, the fluconazole quantification limit is 0.38 mg/kg, the limit of the inhibin is 0.05 mg/kg, and the limit of the restriction is 0.01 mg/kg, the limit of halothiazole was 0.05 mg/kg, the limit of chlorphenolic alcohol was 0.02 mg/kg, is 0.5 mg/kg.

9.2 Recovery

The addition rates of the nine heterocyclic pesticides in tea are shown in Appendix B when different levels are added.

Appendix A

(Informative)

Standard chromatogram 18.41 min - atrazine 21.09 min-vinyl mushroom 25.46 min - Pythium

25.67 Min-fluconazole

27.33 Min-imazalazole

28.30 Min-buprofezin

32.20 Min, 32.58 min-propiconazole

39.12 Min-chlorophenyl pyruvate

41.64 Min-da acarb

Figure A.1 SIM chromatograms of nine heterocyclic pesticide standards

Appendix B

(Informative)

Addition Recovery Rate of 9 Kinds of Heterocyclic Pesticides in Tea

Table B.1 Recovery rates of nine heterocyclic pesticides in tea

Pesticide name Add concentration/(mg/kg) Recovery rate /% Pesticide name Add concentration /(Mg/kg) Recovery rate/ % Atrazine 0.02 89.5-99.2 Vinyl fungus 0.02 80.1-89.7 0.2 90.4-96.4 0.2 79.5-86.7 2.0 92.3-111.4 2.0 94.8-105.4 Pythium 0.02 93.5-97.3 Fluorobenzazole 0.38 80.2-87.9 0.2 92.3-96.6 3.0 78.9-84.4 2.0 92.5-98.5 30 76.6-87.9 Antimycin 0.05 78.8-85.6 Buprofezin 0.01 95.1-99.3 0.5 75.1-83.8 0.1 93.5-99.8 5.0 72.6-79.6 1.0 94.4-103.5 Propiconazole 0.05 81.1-91.7 Chlorophenylpyrimidinol 0.02 96.9-112.4 0.5 95.7-108.2 0.2 103.5-116.2 5.0 96.4-105.8 2.0 99.2-106.7 Pyridaben 0.25 88.6-94.1 2.5 90.2-94.8 20 87.2-93.8 Appendix C (Normative appendix) Laboratory repeatability requirements

Table C.1 Laboratory repeatability requirements

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

Table D.1 Inter-laboratory reproducibility requirements

Measured component content Mg/kg Precision <=0.001 54 > 0.01 > 1 19