Determination of Organochlorine Pesticide Residues

Organochlorine pesticides are organic insecticides and fungicides that contain chlorine atoms in their composition.

The pesticide residue determination methods for DDT, BHC and pentachloronitrobenzene included in the "Chinese Pharmacopoeia" use classic salting-out extraction, sulfonation purification, capillary gas chromatographic separation, and ECD detector detection

(1) Test preparation

1.

2.

3.

(2) Determination of organochlorine pesticide residues (accepted by the Pharmacopoeia)

1.

(1) Chromatographic conditions and system suitability test: elastic quartz capillary column with (14%-cyanopropyl-phenyl) methyl polysiloxane or (5% phenyl) methyl polysiloxane as the fixed liquid (30mx0.

(2) Preparation of reference substance stock solution: accurately weigh BHC (α-BHC, β-BHC, γ-BHC, δ-BHC), DDT (p,p'-DDE, p ,p'-DDD, o,p'-DDT, p,p'-DDT) and pentachloronitrobenzene (PCNB) pesticide reference substance in appropriate amount, respectively made with petroleum ether (60～90℃), each 1ml contains about 4～5ug of solution is ready

(3) Preparation of mixed reference substance stock solution: accurately measure 0.

(4) Preparation of mixed reference substance solution: accurately measure the above-mentioned mixed reference substance stock solution and use petroleum ether (60～90℃) to make a solution containing 0ug, 1ug, 5ug, 10ug, 50ug, 100ug, 250ug per 1L , That is

(5) Preparation of test product solution: medicinal materials or decoction pieces: take the test product, pulverize it into powder (pass through a No.

(6) Preparation: Take the test product, grind it into a fine powder (chop the honey pill, and directly measure the liquid), accurately weigh an appropriate amount (equivalent to 2g of medicinal materials), and prepare it according to the above-mentioned test product solution preparation method.

(7) Determination method: Precisely draw 1ul each of the test solution and the mixed reference solution of the corresponding concentration, and inject it into the gas chromatograph, and calculate the 9 kinds of organochlorine pesticide residues in the test product according to the external standard method (Figure 13-4)

2.

(1) Chromatographic conditions and system suitability test: the analytical column uses 50% phenyl and 50% dimethyl polysiloxane as the fixed liquid elastic quartz capillary column (30m×0.
25mm×0.
25um), and the verification column is 100% The elastic quartz capillary column (30m×0.
25mm×0.
25um) with dimethyl polysiloxane as the fixed liquid, 63Ni-ECD electron capture detector
.
The temperature of the injection port is 240°C, the temperature of the detector is 300°C, and the flow rate is constant pressure mode (initial flow rate is 1.
3ml/min)
.
Program the temperature to 70°C initially, keep it for 1 minute, raise 10°C per minute to 180°C, hold it for 5 minutes, then raise it to 220°C at 5°C per minute, and finally raise it to 280°C at 100°C per minute and hold it for 8 minutes
.
The number of theoretical plates calculated by α-BHC should not be less than 1×10, and the resolution of two adjacent chromatographic peaks should be greater than 1.
5
.

(2) Preparation of reference substance stock solution: accurately weigh an appropriate amount of the pesticide reference substance in Table 13-1, and use isooctane to make the concentration as shown in Table 13-1
.

Table 13-1 Concentration, relative retention time and detection limit reference value of 22 kinds of organochlorine pesticide reference substance stock solutions

Note: The relative retention time of each reference substance is calculated with endosulfan sulfate as the reference peak
.

(3) Preparation of mixed reference substance stock solution: accurately measure 1ml each of the above reference substance stock solution, put it in a 100ml measuring flask, dilute to the mark with isooctane, shake well, and get it
.

(4) Preparation of mixed reference substance solution: accurately measure the above-mentioned mixed reference substance stock solution, and use isooctane to make a solution containing 10ug, 20ug, 50ug, 100pg, 200ug, 500pg per 1L, and then obtain (where β -BHC, Endrin, p,p'-Didi, o,p'-DDT (each 1L contains 20ug, 40ug, 100ug, 200ug, 400ug, 1000ug)
.

(5) Preparation of the test solution: Take the test product, pulverize it into powder (pass through a No.
3 sieve), take about 1.
5g, accurately weigh it, and place it in a 50ml polystyrene centrifuge tube with a stopper.
Add 10ml of water.
Mix well, leave it for 2 hours, add 15ml of acetonitrile precisely, shake vigorously for 1 minute, then add the pre-weighed mixed powder of 4g anhydrous magnesium sulfate and 5g sodium chloride , shake again vigorously for 1 minute, centrifuge (4000 Revolution/min) 1 minute
.
Precisely aspirate 10ml of the supernatant, concentrate it to near dryness under reduced pressure at 40°C, transfer it to a 10ml measuring flask with a cyclohexane -ethyl acetate (1:1) mixed solution, and add cyclohexane- ethyl acetate (1: 1) Mix the solution to the mark, shake well, transfer to a centrifuge tube pre-added with 1g of anhydrous sodium sulfate , shake, leave it for 1 hour, centrifuge (filter if necessary), take 5ml of supernatant and pass it through a gel permeation chromatography column [400mm×25mm, with BIO-BeadsS-X3 packing inside; Cyclohexane-ethyl acetate (1∶1) mixed solution as mobile phase; flow rate of 5.
0ml per minute] Purification, collecting eluent for 18-30 minutes , Concentrate under reduced pressure in a water bath at 40℃ to near dryness, add a small amount of n-hexane to replace twice, add 1ml of n-hexane to dissolve, transfer to Florisil solid phase extraction cartridge [1000mg/6ml, use n-hexane-acetone (95 : 5) Pre-wash with 10ml mixed solution and 10ml n-hexane ], wash the residue with n-hexane 3 times, 1ml each time, transfer the washing liquid to the same Florisil solid phase extraction cartridge, and then use n-hexane -acetone (95:5) 10ml of mixed solution is eluted, collect all the eluates, blow on a nitrogen blowing instrument to nearly dry, add isooctane to make the volume up to 1ml, vortex to dissolve, and it is ready
.

(6) Determination method: Precisely draw 1ul each of the test solution and the mixed reference solution respectively, and inject it into the gas chromatograph, and calculate the pesticide residues in the test product according to the external standard curve method
.

(7) Limit: Unless otherwise specified, the total BHC (the sum of α-BHC, β-BHC, γ-BHC, δ-BHC) per 1kg of Chinese medicinal materials or decoction pieces shall not exceed 0.
2mg; total DDT ( The sum of p, p'-DDE, p, p'-DDD, o, p'-DDT, p, p'-DDT) shall not exceed 0.
2mg; Quintozene shall not exceed 0.
1mg; hexachloro Benzene (Hexachlorobenzene) must not exceed 0.
1mg; Heptachlor (Heptachlor), cis-epoxide (Heptachlor-exo-epoxide) and trans-epoxide (Heptachlor-endo-epoxide) must not exceed 0.
05mg; The sum of Aldrin and Dieldrin shall not exceed 0.
05mg; Endrin shall not exceed 0.
05mg; cis-Chlordane and trans-Chlordane The sum of oxy-Chlordane and oxy-Chlordane shall not exceed 0.
05 mg; the sum of α-Endosulfan, β-Endosulfan and Endosulfan sulfate shall not exceed 3 mg
.

[Note]

(1) When pesticides are detected in the test product, the detected results can be confirmed in the verification column and then quantified
.
When necessary, it can be confirmed by gas chromatography-mass spectrometry
.

(2) The sample recovery rate should be between 70% and 120%
.