Soil and sediments. Determination of acrolein, acrylonitrile and acetonitrile. Gas chromatography (1)

1.

This method is suitable for the determination of acrolein , acrylonitrile and acetonitrile in soil and sediment

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

For the sample sealed in the headspace bottle, at a certain temperature, the acrolein , acrylonitrile and acetonitrile contained in the sample volatilize to the upper space, and reach the thermodynamic dynamic equilibrium in the three phases of gas, liquid and solid

3.

(1) Experimental water

Freshly prepared deionized or distilled water without organic matter

(2) Sodium chloride : pure superior grade

(3) Methanol : chromatographically pure grade

(4) Phosphoric acid : pure superior grade

(5) Matrix modifier

Measure 500 mL of experimental water, add drops of phosphoric acid to adjust to pH ≤ 2, then add 180 g of sodium chloride , dissolve and mix

(6) Mixed standard solution of acrolein , acrylonitrile and acetonitrile : p=2000mg/L, the solvent is methanol, and it should be stored under -18℃ and protected from light

(7) Quartz sand: 40-100 mesh

Four, instruments and equipment

(1) Gas chromatograph: with hydrogen flame ionization detector

(2) Chromatographic column: Chromatographic column model: HP-1 (60m×0.

(3) Headspace sampler: with temperature and time control functions
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(4) Reciprocating oscillator: The oscillation frequency is 150 times/min, and the headspace bottle can be fixed
.

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

(6) Oven
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Five, pre-treatment

(1) Sample preparation

The high and low content samples are determined based on the preliminary measurement results at the time of sampling
.

1.
Low content samples

Take out the sample bottle, after returning to room temperature, weigh 2g of the sample into the headspace bottle, quickly add 10mL matrix modifier, seal it immediately, and oscillate on a shaker at a frequency of 150 times/min for 10 minutes for testing
.

2.
High content samples

If the initial screening of volatile organic compounds on site is high content or the initial screening is low content but the measurement result is greater than 300mg/kg, it should be regarded as a high content sample
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The high-content sample is prepared as follows; another unopened sample is taken, and after returning to room temperature, 2.
0 g of the sample is weighed and placed on a headspace bottle towel, and 10 mL of methanol is quickly added , sealed, and shaken on a shaker for 10 minutes
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After standing and settling, pipette 1 to 2 mL of methanol extract (if necessary, centrifuge first and then take the supernatant) into a 2 mL brown glass bottle
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The extract is stored in the dark at 4°C.
The storage period of acrolein is 2 days.
If only acetonitrile and acrylonitrile are tested , it can be stored for 7 days
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After returning the methanol extract to room temperature before analysis, add 2g of quartz sand, 10mL matrix modifier and 10-200uL of methanol extract to the empty headspace bottle, seal it immediately, and perform 150 times/min on the shaker.
The frequency oscillates for 10 minutes and is to be tested
.

(2) Determination of dry matter content

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