Determination of 65 kinds of volatile organic compounds in soil and sediments. Purge and trap gas chromatography-mass spectrometry (1)

1.

This method is suitable for the determination of volatile organic compounds in soil and sediments

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

Second, the principle of the method

The volatile organic compounds in the sample are purged with high-purity helium (or nitrogen) to be enriched in the trapping tube.

3.

(1) Methanol : pesticide residue level

(2) Quartz sand: 40-100 mesh, heated at 450°C for 4 hours, placed in a desiccator to cool to room temperature, sealed and stored in a clean reagent bottle

(3) Ultra-pure water: no VOCs interference, can be purchased or prepared in the laboratory

(4) Magnetic stirrer: wash with methanol and use after soaking in ultrapure water

(5) Mixed standard solution of volatile organic compounds: p=1000ug/mL, and the solvent is methanol

(6) Internal standard: mixed standard of fluorobenzene, 1,4-dichlorobenzene-d ₄ , and chlorobenzene-d ₅ , p=1000ug/mL, and the solvent is methanol

(7) Substitute: Toluene-d ₈ , p-bromofluorobenzene mixed standard, p=1000ug/mL, and the solvent is methanol

(8) for bromofluorobenzene : p = 10ug / mL, the solvent is methanol

Four, instruments and equipment

(1) Purge and trap instrument (with ten soil sample injection function)

(2) EI source single quadrupole gas chromatography mass spectrometer

(3) Balance: the accuracy is 0.

(4) Oven
.

Five, pre-treatment

(1) Sample preparation

1.
Low-content samples (samples with predicted content lower than 1000ug/kg)

Take out the sample in the laboratory.
After returning to room temperature, take 1～5g sample for direct measurement; weigh 5g sample into a 40mL purge trap bottle with a magnetic stirrer, quickly add 5mL ultrapure water to the bottle, add The substitute and internal standard solution (the recommended mass concentration on the machine is the same as the mass concentration of the substitute and internal standard in the standard series), immediately seal and cover, and wait for purge and trap-GC/MS detection
.

2.
High content samples (samples with predicted content higher than 1000ug/kg)

When it is preliminarily determined that the volatile organic content in the sample is greater than 1000ug/kg, take about 5g of the sample in a pre-weighed 40mL sample bottle and weigh it (accurate to 0.
01g)
.
Quickly add 10.
0 mL of methanol, cap the bottle and shake for 2 minutes
.
After standing to settle, pipette about 1 mL of the extract into a brown glass bottle and seal it
.
Take 10.
0-100uL extract, add internal standard and substitute, measure 5.
0mL ultrapure water as sample, put it into 40mL sample bottle, wait for purge and trap-GC/MS detection
.

(2) Determination of dry matter content

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

Related Links: Determination of 36 Volatile Organic Compounds and 35 Volatile Halogenated Hydrocarbons in Soils and Sediments Headspace Gas Chromatography-Mass Spectrometry (3)