Solid waste leachate-determination of polychlorinated biphenyls-gas chromatography (2)

Six, analysis and testing

(1) Instrument conditions (for reference only, can be adjusted appropriately according to the actual instrument)

Inlet temperature: 280℃

Sampling method: split injection, split ratio: 10:1

Chromatographic column: HP-5 (30m×0.

Carrier gas: nitrogen, purity>99.

Detector temperature: 300℃

(2) Calibration.

Prepare a standard series of more than 5 points (such as 5.

Table 3-5 Retention time

7.

(1) Qualitative target compound

Qualitatively based on the retention time of each component of the standard material

(2) Quantitative calculation

The target compound is quantified by the internal standard method, and the mass concentration of the target compound in the leachate ρ (ug/L) is calculated according to formula (1)

ρ=ρ _x ×(V _x /V _i ) (1)

Where ρ _x — the mass concentration of the target compound calculated from the calibration curve, ug/L;

V _x —Concentrated constant volume of the extract, mL;

V _i — sampling volume of leaching solution, mL

8.

(1) Calibration curve

Use the linear fitting curve to calibrate, the correlation coefficient should be greater than or equal to 0.

(2) Calibration verification

Before analyzing each batch of samples (up to 20 samples), check the calibration curve with the mass concentration at the middle point of the calibration curve.

(Three) blank

Each batch of samples (up to 20 samples) should be a laboratory blank, and the mass concentration of the target compound in the blank result should be less than the detection limit of the method

(4) Parallel sample determination

Each batch of samples (up to 20 samples) should be subjected to at least one parallel determination, and the relative deviation of the parallel sample determination results should be within 30%
.

(5) Standard addition and standard addition of actual samples are parallel

Each batch of samples (up to 20 samples) should be carried out at least once for actual sample addition and one addition in parallel
.
The actual sample recovery rate should be between 70% and 130%, and the relative deviation of the determination results of the standard spiked parallel sample should be within 30%
.
If the recovery rate of the standard addition does not meet the requirements, but the standard addition meets the requirements in parallel, it means that the sample has a matrix effect, which needs to be noted in the results
.

Nine, matters needing attention

(1) The solvents and reagents used in the experiment have a certain degree of toxicity, especially some PCBs are carcinogenic, so the sample pretreatment process should be carried out in a fume hood, and the operator should do his own protection work
.

(2) The rotary evaporation should not be too fast and the vacuum degree should not be too low, otherwise the recovery rate of low-chlorinated biphenyls will be low
.

(3) Double columns should be used for qualitative analysis of detected samples, and the accuracy of the results should be judged based on the recovery rate of standard addition
.