Determination of multiple residues of organochlorine and pyrethroid pesticides in vegetables (1)

GB/T5009.
146-2008 stipulates the gas chromatography analysis method for 10 kinds of organochlorine pesticides and 6 kinds of pyrethroid pesticide residues in vegetables , which is a representative pesticide multi-residue detection method
.

1.
Purpose requirements

(1) Understand the working principle of gas chromatograph
.

(2) Grasp the principles, procedures and points of attention for the determination of multiple residues of organochlorine and pyrethroid pesticides in vegetables by gas chromatography
.

(3) Understand the selection method of gas chromatograph working conditions
.

2.
Principles of training

The organochlorine and pyrethroid pesticides in the sample are extracted with organic solvents, and the interfering substances are removed by liquid-liquid distribution and chromatography.
The detection is carried out with an electron capture detector, qualitatively based on the retention time of the chromatographic peak, and quantified by an external standard method
.

3.
Training supplies

(1) Gas chromatograph: with electron capture detector (ECD)
.

(2) Organization masher
.

(3) Electric oscillator
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(4) Rotary evaporator (see Figure 1-7 Rotary Evaporator Device Diagram)
.

(5) Conventional utensils: Buchner funnel (Φ80mm); suction filter flask (20mL); cork flask (250mL); separatory funnel (250mL); graduated cylinder (100mL); beaker (150mL); glass funnel (60° , Φ9cm); graduated pipette (5mL)
.

(6) Plastic syringe: 2.
5mL
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(7) Petroleum ether (chromatographically pure)
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(8) Benzene (chromatographically pure)
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(9) Acetone (chromatographically pure)
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(10) Ethyl acetate (chromatographically pure)
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(11) 2% Na ₂ SO ₄ aqueous solution: Weigh 20 g of anhydrous sodium sulfate (analytical purity), dilute the volume to 1 L with distilled water, and dissolve it for later use
.

(12) Flori silica (silica-magnesium adsorbent 60-100 mesh): used for chromatography, burned at 620°C for 4 hours and then used, bake at 140°C for 4 hours before use, inactivate by adding 5% water while it is hot, and shake evenly , Sealed and stored in a ground bottle
.

(13) Pesticide standards (purity ≥99%): α-666, β-666, γ-666, δ-666, heptachlor, aldrin, p, p'-DDT, p, p'-DDD, p, p'-DDE, O, p'-DDT, fenpropathrin , cyhalothrin (commonly known effort), permethrin (alias permethrin), cypermethrin , fenvalerate , deltamethrin Ester
.

(14) Standard solution: Weigh the standard substance in (13) accurately, dissolve it with benzene and make a 1mg/mL stock solution
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(15) Qualitative filter paper: check without interference (Φ15cm)
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(16) Microporous membrane: 0.
45um (organic phase)
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4.
Safety reminder

Ethyl acetate is flammable, explosive, volatile, irritating and sensitizing; petroleum ether is extremely flammable, can cause peripheral neuritis, and has strong irritation to the skin; n-hexane is flammable and explosive, and has anesthetic and irritating effects , Long-term exposure can cause peripheral neuritis; acetone mainly inhibits the central nervous system and has an anesthetic effect; pre-treatment operations should be carried out in a fume hood.
Open flames, inhalation, and skin contact should be avoided
.

The liquid waste produced in the experiment must be treated as hazardous waste