Determination of 60 semi-volatile organic compounds in soils and sediments by gas chromatography-mass spectrometry (1)

1.

This method is suitable for the determination of semi-volatile organic compounds in soil and sediment.

After the applicability of other semi-volatile organic compounds has been verified, this method can also be used for analysis

Second, the principle of the method

Using pressurized fluid extraction, the semi-volatile organic compounds in the sample are extracted with a mixed solvent of dichloromethane and acetone , and the extract is processed by concentration, purification, etc.

3.

(1) Dichloromethane : pesticide residue level

(2) Acetone : pesticide residue level

(3) Anhydrous sodium sulfate : pure superior grade, burned at 450°C for 4 hours and then placed at room temperature for use

(4) Diatomite: 60 mesh

(5) Extraction cell gasket: soak in dichloromethane and ultrasonic for three times, dry, and it can be used after the blank experiment passes

(6) Quartz sand: 40-100 mesh, burn it in a muffle furnace at 450℃ for 4h before use

(7) Copper sheet: Use dilute hydrochloric acid solution to remove the oxides on the surface of the copper powder before use , rinse with experimental water to remove the acid, and rinse with acetone , then dry it with nitrogen until it is used.

(8) Semi-volatile organic compound standard solution, p=1000ug/mL, and the solvent is dichloromethane

(9) Substitutes: nitrobenzene-dy, 2-fluorobiphenyl, 2,4,6-tribromophenol, 4,4'-terphenyl-d14 mixed standard solution, p=1000ug/mL, solvent is n-hexane Alkane

(10) Internal standard: 1,4-dichlorobenzene-d ₄ , naphthalene-d ₈ , acenaphthene-d ₁₀ , ch-d ₁₂ , perylene-d ₁₂ , phenanthrene-d ₁₀ mixed standard solution, p=1000ug/mL , The solvent is n-hexane

(11) decafluoro triphenylphosphonium : p = 10ug / mL, the solvent is n-hexane

Four, instruments and equipment

(1) Pressurized fluid extraction device
.

(2) EI source single quadrupole gas chromatography mass spectrometer
.

(3) Chromatographic column: HP-5MSUI, 30m×0.
25mm×0.
25um
.

(4) Balance: the accuracy is 0.
01g
.

(5) Oven
.

Five, pre-treatment

(1) Sample preparation

Determination of Organochlorine Pesticides in Soils and Sediments Gas Chromatography (1) -Sample Preparation
.

(2) Pressurized fluid extraction

Weigh about 20g fresh/freeze-dried sample, add 8-10g diatomaceous earth and mix well, place it in the extraction tank, add the substitute solution (the mass concentration of the machine is consistent with the mass concentration of the substitute in the standard series), continue Add Florida diatomaceous earth until the extraction tank is filled, and then perform pressurized fluid extraction according to the standard requirements
.

The reference operating conditions are as follows:

Extraction solvent: dichloromethane - acetone equal volume mixed solvent, extraction temperature: 100℃, extraction pressure 1500psi, static extraction time 10min, elution volume 60% of the pool volume, nitrogen purge for 60s, extraction cycle 2 times, collection and extraction Liquid
.

After the extract is dehydrated by anhydrous sodium sulfate (burned at 450°C for 4 hours), it is concentrated by rotary evaporation to about 1 mL, and the internal standard solution is added (the mass concentration on the machine is recommended to be consistent with the internal standard mass concentration in the standard series).
Test on the machine
.

(3) Purification

For each category of compounds, exclusive purification methods should be used for processing
.
If the color of the extract is dark, Flori silica column, silica gel column, gel permeation purification column, etc.
can be used
.
When the sediment sample contains a large amount of organic sulfur interference, it can be removed by activated copper sheet
.
After purification, the sample solution is concentrated to about 1 mL, and the internal standard solution is added (the on-board mass concentration is recommended to be consistent with the internal standard mass concentration in the standard series), and it is ready to be tested on the machine
.

(4) Determination of dry matter content

Determination of Organochlorine Pesticides in Soils and Sediments Gas Chromatography (1) ——Determination of Dry Matter Content
.