Determination of 65 kinds of volatile organic compounds in soil and sediments. Purge and trap gas chromatography-mass spectrometry (3)

7.

(1) Qualitative target compound

Qualitatively based on the retention time of each component of the standard substance and the comparison of the standard mass spectrum

(2) Quantitative calculation

1.

The relative response factor RRFi of the target (or substitute) in the ith point of the standard series is calculated according to formula (1)

In the formula, Ai——the response value of the quantitative ion of the ith target (or substitute) in the standard series;

AISi——The response value of the internal standard quantitative ion corresponding to the i-th point monthly standard substance (or substitute) in the standard series;

pIS——the mass concentration of the internal standard in the standard series;

Pi——the mass concentration of the target substance (or substitute) at the i-th point in the standard series

The average relative response factor of the target (or substitute) is calculated according to formula (2)

In the formula, n——the number of standard series points

2.

When the target (or substitute) is calibrated with the average response factor, the mass concentration pes (ug/L) of the daily standard (or substitute) in the sample is calculated according to formula (3)

In the formula, Ax——the response value of the quantitative ion of the target (or substitute);

AIS——The response value of the internal standard quantitative ion corresponding to the target (or substitute);

pIS——the mass concentration of internal standard substance, ug/L;

——The average relative response factor of the target (or substitute)

3.

Where pi-the mass concentration of the target compound calculated from the calibration curve, mg/L;

V——The constant volume of the sample, mL;

m——the mass of soil sample (wet weight), g;

wdm——The dry matter content of the soil sample, %

8.

(1) At least one transportation blank and full procedure blank should be collected for each batch of samples

①The concentration of the target substance is less than the detection limit of the method;

②The concentration of the target substance is less than 5% of the relevant environmental protection standard limit;

③The concentration of the target substance is less than 5% of the sample analysis result

(2) Before analyzing each batch of samples or within 24 hours, it is necessary to check the performance of the instrument and measure the calibration confirmation standard sample (p-bromofluorobenzene) and blank sample

(3) The configuration of the standard series should be at least 5 points, and the configuration mass concentration range should cover the mass concentration of the sample to be tested
.
If the average relative response factor is used for quantification, the RSD of the relative response factor should not exceed 30%; if the least square method is used for quantification, the curve correlation coefficient needs to be no less than 0.
990
.

(4) Each batch of samples should be subjected to parallel analysis and matrix spike analysis
.
The recovery rate of standard addition of substitutes and matrix in all samples is in the qualified range of 70% to 130%
.
For a parallel sample, the relative deviation of the substitute in the parallel sample should be within 25%
.

Related Links: Determination of 65 Volatile Organic Compounds in Soils and Sediments Purge and Trap Gas Chromatography-Mass Spectrometry (2)