Solid waste leachate-determination of polychlorinated biphenyls-gas chromatography (1)

1.

This method is suitable for the determination of 19 kinds of polychlorinated biphenyls (PCBs) in solid waste leachate .

Second, the principle of the method

Use dichloromethane to extract PCBs in the leachate, purify with concentrated sulfuric acid , and analyze PCBs in the sample by gas chromatography electron capture detector method (GC-ECD).

3.

(1) N-hexane : pesticide residue level

(2) Dichloromethane : pesticide residue level

(3) Sodium chloride : pure superior grade

(4) Anhydrous sodium sulfate ; high-grade pure

(5) Concentrated sulfuric acid ρ(H ₂ SO ₄ )=1.

(6) Concentrated nitric acid: pure superior grade

(7) Extractant: Add a mixture of concentrated sulfuric acid and concentrated nitric acid with a mass ratio of 2:1 to ultrapure water (about 2 drops of 1L water) to make the pH 3.

(8) 5% sodium chloride solution: ρ(NaCl)=0.

(9) PCB mixed standard solution: ρ=100ug/mL, the solvent is n-hexane

(10) Substitute: PCB 209, ρ=100ug/mL, solvent is n-hexane

(11) The experimental water is newly prepared deionized water without target

Four, instruments and equipment

(1) Gas chromatograph: with dual-split/splitless injection port, equipped with dual electron capture detector (ECD)

(2) Chromatographic column: HP-5 (30m×0.
32mm×0.
25um), or other equivalent capillary columns
.

(3) Extraction equipment: liquid-liquid extraction oscillating device, flipping oscillator
.

(4) Concentrating device: rotary evaporator or other concentrating device
.

(5) Separation funnel: with polytetrafluoroethylene (PTFE) piston
.

Five, pre-treatment

(1) Preparation of solid waste leachate

"Semi-Volatile Organic Compound Analysis Technology-Preparation of Sulfuric Acid and Nitric Acid from Leachate"

(2) Sample extraction

Take 100 mL of the extract and add the substitute, 5 g of sodium chloride , and 15 mL of dichloromethane .
After liquid-liquid extraction, the organic phase is dried over anhydrous sodium sulfate, the filtrate is collected, and the extraction is repeated twice.
The extracts are combined and combined.
Concentrate to about 4 mL, add 4 mL of n-hexane , and continue to concentrate to 1 mL for GC-ECD analysis and determination
.
If the color of the sample is darker after extraction, it needs to be purified by sulfuric acid before it can be analyzed on the machine
.

(3) Purification

Dilute the concentrated solution to 7mL with n-hexane , transfer it to a 20mL glass tube, add 8mL concentrated sulfuric acid , vortex and mix well, centrifuge (speed 3000r/min, time 1min), discard the lower layer of sulfuric acid
.
If there is still color in the sulfuric acid layer, repeat the above operation until the sulfuric acid layer is colorless
.
Add 8mL of 5% sodium chloride aqueous solution to the glass tube to wash the organic phase, vortex and mix well, centrifuge (speed 3000r/min, time 1min), discard the water phase, repeat the above operation until the organic phase is neutral
.
After the organic phase was dehydrated by anhydrous sodium sulfate , it was concentrated to 1 mL by nitrogen blowing
.

Related Links: Solid Waste—Determination of Organophosphorus Pesticides—Gas Chromatography (2)