GB 23200.40-2016Food safety national standard -- Determination of organophosphorus and organochlorine pesticide residues in cola drinks -- Gas chromatographic method (English PDF)

4.1 Reagents

4.1.1 n-hexane (C6H14). chromatographic purity.

4.1.2 Methanol (CH3OH). Chromatographic Purification.

4.1.3 ethyl acetate (C4H8O2). excellent grade pure.

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

4.1.5 Sodium chloride (NaCl).

4.1.6 Sodium hydroxide (NaOH).

4.1.7 concentrated sulfuric acid (H2SO4). excellent grade pure.

4.2 Solution preparation

4.2.1 Methanol - Aqueous solution (5 95, V/V). Take 5 mL of methanol and mix with 95 mL of water.

4.2.2 Methanol - Aqueous solution (10 90, V/V). Take 10 mL of methanol and mix with 90 mL of water.

4.2.3 Sodium hydroxide solution (1 mol/L). 20 g of sodium hydroxide, dissolved in water and set to 500 mL.

4.3 Standards

4.3.1 Pesticide Reference Material. See Appendix A.

4.4 Standard solution preparation

4.4.1 Organophosphorus pesticide standard solution

4.4.1.1 Organophosphorus pesticide standard stock solution. accurately weighed the amount of dichlorvos, chlorpyrifos, malathion, parathion, respectively with C the ketone is dissolved and fixed in a brown volumetric flask at a concentration of 1 000 mg/L and the stock is stored below -18 ° C.

4.4.1.2 organic phosphorus mixed standard intermediate solution. accurate absorption of appropriate dichlorvos, chlorpyrifos, malathion, parathion standard stock solution in a brown volumetric flask, the concentration of various organophosphorus pesticide standard solutions is 10 mg/L, and the intermediate solution is at -18 ° C Save the following.

4.4.1.3 organic phosphorus mixed standard working solution. with ethyl acetate mixed standard intermediate solution as needed dilution, prepared for the four kinds of Machine phosphorus pesticide mixed standard working solution, mixed standard working solution in 0 °C ~ 4 °C preservation.

4.4.2 Organochlorine pesticide standard solution

4.4.2.1 mixed solution of organochlorine pesticide standard solution. remove the appropriate volume of heptachlor, hexachlorobenzene, 666 mixed standard solution, pentachlor Nitrobenzene standard solution in a brown volumetric flask, with n-hexane volume to the scale, a variety of organochlorine pesticide standard solution concentration of 10 mg/L, the intermediate solution is stored below -18 ° C.

4.4.2.2 organic chlorine mixed standard working solution. with n-hexane mixed standard intermediate solution as needed dilution, formulated as organic chlorine farmers Drug mixed standard working solution, mixed standard working solution stored at 0 °C ~ 4 °C.

4.5 Materials

4.5.1 HLB solid phase extraction cartridge. 60 mg, 3 mL, or equivalent.

6.1 Extraction

Take the cola sample in a beaker, place it for 60 min, and stir the exhaust with a glass rod. Accurately weigh 150 g (accurate to 0.01 g) cola Sample, add 1 mol/L sodium hydroxide solution to adjust the pH of the solution to about 7. Transfer the neutralized cola sample to 500 mL in the separatory funnel, add 15 g of sodium chloride and 100 mL of ethyl acetate, shake vigorously for 2 min and leave for 10 min.

Layer of organic phase, pre-filled anhydrous sodium sulfate column (in the glass sand core funnel filled with about 15 g anhydrous sodium sulfate, and 20 mL B Ethyl acetate rinse) was collected in a 500 mL round bottom flask. In the separatory funnel,.200 mL of ethyl acetate was added in two portions, 100 mL each time, Repeat the above extraction steps, the combined extract in 40 °C water bath rotation to 3 mL ~ 4 mL, transferred to 15 mL centrifuge tube, with 9 ML n-hexane was washed three times in a round-bottomed flask, and the combined washings were mixed in a 15 mL centrifuge tube and blown nitrogen to near dry at 40 ° C.

6.2 Purification

6.2.1 Determination of organophosphorus pesticide sample solution

HLB solid phase extraction column before use, respectively, with ethyl acetate 3 mL leaching once, 3 mL of methanol and 3 mL of water pretreated twice to keep the column Body moist. The extract of 6.1 was dissolved in 5 mL of a 10% aqueous methanol solution and passed through an HLB solid phase extraction column at 1 drop/sec.

And the tube was rinsed with 10 mL of 5% aqueous methanol and the HLB column was discarded. The rinsing solution from the HLB column was discarded and the vacuum was drained 10 min. Eluting with 9 mL of ethyl acetate. The eluate was collected in a 15 mL centrifuge tube, 3 g of anhydrous sodium sulfate was added, shaken for 3 min, 5000 r/min under the conditions of centrifugation 2 min, the solution transferred to another centrifuge tube, in the 40 °C water bath blowing nitrogen concentrated to near dry, with acetic acid B the ester was set to 1.0 mL and the gas chromatographic FPD was determined.

6.2.2 Determination of organochlorine pesticides Sample solution purification

The extract of 6.1 was dissolved in 1 mL of n-hexane, 0.5 mL of concentrated sulfuric acid was added, the mixture was gently shaken and centrifuged at 5000 r/min for 5 min After taking the upper organic phase into the gas chromatography ECD determination, such as the purification effect is not sufficient, can be added again concentrated sulfuric acid purification.

6.3 Determination

6.3.1 Gas chromatographic electron capture detection instrument reference conditions

A) Column. DB-5 quartz capillary column. 30 m x 0.32 mm (inner diameter), film thickness 0.25 µm, or equivalent.

B) Column temperature. 80 ° C (1 min) 30 ° C/min.180 ° C 3 ° C/min 205 ° C (4 min) 2 ° C/min 210 ° C (1 min), postrun.

280 ° C (1 min);

C) Inlet temperature. 250 ° C.

D) Detector temperature. 300 ° C.

E) Carrier gas. nitrogen, purity 99.999%, constant pressure 0.135Mpa.

F) Injection volume. 1 µL.

G) Injection method. split injection, split ratio of 12. 1.

6.3.2 Gas chromatographic flame photometric detection instrument reference conditions

A) Column. DB-1701 quartz capillary column. 30 m x 0.32 mm (inner diameter), film thickness 0.25 µm, or equivalent.

B) Column temperature. 90 ° C (1 min) 30 ° C/min. 2.0 ° C (8 min) 10 ° C/min 240 ° C, postrun. 280 ° C (5 min).

C) Inlet temperature. 250 ° C.

D) Detector temperature. 250 ° C.

E) Carrier gas. nitrogen, purity 99.999%, constant pressure 0.071Mpa.

F) Injection volume. 1 µL.

G) Injection method. no split into the sample, 1.0 min after the opening of the diversion valve, purge flow 50 mL/min.

6.3.3 Determination and confirmation of chromatography

The measured solution was subjected to gas chromatographic electron capture detection and gas chromatography flame photometric detection, according to the sample solution of organic phosphorus or organic chlorine Residual content of the situation, selected peak area similar to the standard working solution. Standard working solutions and residual reactions of organophosphorus or organochlorine residues in the sample solution the values shall be within the linear range of the instrument's detection. For the mixed standard working solution and sample solution, such as volume fractionation method, the external standard method.

The retention times of organophosphorus and organochlorine pesticides are shown in Appendix A under 6.3.1 and 6.3.2 chromatographic conditions. 10 µg/L organic phosphorus and organic chlorine mixed standard the chromatogram of the quasi-working solution is shown in Appendix B, Figure B.1, Figure B.2, respectively.

6.4 Blank experiment

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

9.1 Limit of limits

The limit of organic phosphorus and organochlorine pesticides is 0.0001 mg/kg.

9.2 Recovery

When the levels were 0.0001 mg/kg, 0.0002 mg/kg, 0.0005 mg/kg, the addition of organophosphorus, organochlorine pesticide compounds See Appendix C. for the yield.

Appendix A

(Informative)

Organic phosphorus, organochlorine pesticide basic information and retention time

Table A.1 Basic information and retention times for organophosphorus pesticides

Serial number

Pesticide Chinese

name

Pesticide English

name

CAS number Molecular formula Molecular retention time Min Dichlorvos 62-73-7 C4H7Cl2O4P 220.98 4.750 2 chlorpyrifos 2921-88-2 C9H11Cl3NO3PS 350.59 11.246

3 Malathion 121-75-5 C10H9O6PS2 330.36 12.028

4 Parathion 56-38-2 C10H14NO5PS 291.26 13.250

Table A.2 Basic information and retention times of organochlorine pesticides

Serial number

Pesticide Chinese

name

Pesticide English

name

CAS number Molecular formula Molecular weight keep time Min 1 alpha-hexahydrate alpha-HCB 319-84-6 C6H6Cl6 290.83 9.657 2 hexachlorobenzene Hexachlorobenz Ene 118-74-1 C6Cl6 284.78 9.924 3 beta-hexamethylene beta-HCB 319-85-7 C6H6Cl6 290.83 10.378 4 gamma-hexahydrate gamma-HCB 58-89-9 C6H6Cl6 290.83 10.591

5 Pentachloronitrobenzene Quintozene 82-68-8 C6Cl5NO2 295.34 10.749 6 delta-hexahydrate delta-HCB 319-86-8 C6H6Cl6 290.83 11.284

7 Hexachlor Heptachlor 76-44-8 C10H5Cl7 373.32 13.072 Appendix B (Informative) Organic phosphorus, organic chlorine pesticide reference substance chromatogram

Figure B.1 10 µg/L organic phosphorus pesticide standard solution chromatogram

1. dichlorvos; 2. chlorpyrifos; 3. malathion; 4. parathion.

Figure B.2.10 µg/L Organic Chlorine Pesticide Standard Solution Chromatogram

1. a-six six six; 2. hexachlorobenzene; 3. beta-666; 4. pentachloronitrobenzene; 5. gamma-666; 6.

Appendix C

(Informative)

The recovery rate of organic phosphorus and organochlorine pesticides in cola

Table C.1 Recovery of organic phosphorus and organochlorine pesticides in cola

No. Compound name Recovery rate range,% 1 dichlorvos 72.0% ~ 105.0 2 chlorpyrifos 75.8% ~ 98.0 3 malathion 64.0% ~ 88.0 4 parathion 75.0% ~ 92.0 5 alpha - 6 6 81.5% ~ 99.0 6 hexachlorobenzene 85.0% ~ 106.0 7 ~ 6 6 6 73.0% ~ 98.0 8 ~ 6 6 6 84.0% ~ 104.6

9 Pentachloronitrobenzene 81.5% ~ 98.0 10 delta-six six six 76.0% ~ 97.0