HJ 1042-2019Ambient air and waste gas - Determination of trimethylamine - Solvent absorption-Headspace/gas chromatography (English PDF)

7.1 Sample collection

7.1.1 Air samples

Arrangement, sampling frequency and sampling of air sampling points for ambient air samples and fugitive emission monitoring points of fixed pollution sources the operation is performed in accordance with the relevant regulations of HJ 194, HJ 905 and HJ/T 55.

After the sampling device, two 25 ml bubble absorption bottles (6.4) each containing 10.0 ml of absorption liquid (5.8) were connected in series, and samples were taken with air.

The device (6.2) continuously samples for at least 20 minutes at a flow rate of 0.5 L/min to 1.0 L/min.

7.1.2 Exhaust gas samples

Determination of sampling locations and sampling points for exhaust gas monitoring of fixed pollution sources, determination of exhaust parameters and sampling operations the relevant regulations of GB 14554, GB/T 16157, HJ 905 and HJ/T 397 are implemented. The sampling device is shown in Figure 1.

After the sampling device, two 75 ml bubble absorption bottles (6.4) each containing 50.0 ml of absorption liquid (5.8) are connected in series, and the pipeline is connected it should be as short as possible. According to the gaseous pollutant collection method, use a flue gas sampler (6.1) at a flow rate of 0.5 L/min ~ 1.0 L/min Continuous sampling for at least 20 min. When sampling, heat and keep the sampling tube at 120 ° C to avoid condensation of water vapor before the absorption bottle.

Flow measurement and control device Sampling tube with heating device Absorption fluid Exhaust pipe Three-way valve Bypass absorption bottle Three-way valve

Figure 1 Sampling diagram of exhaust gas sample

7.1.3 Full Program Blank

Bring the absorption bottle with the same batch of absorption liquid (5.8) to the sampling site, not connected to the sampler, and take it Back to the laboratory for testing.

7.2 Sample preservation

The analysis should be completed as soon as possible after the sample is collected, otherwise it should be sealed and refrigerated and stored below 4 ° C, and the analysis should be completed within 7 days.

7.3 Sample preparation

7.3.1 Air sample

Transfer the sample solution (7.1.1) in two absorption bottles into two 10 ml colorimetric tubes, and use the appropriate amount of absorption solution (5.8) the inner wall of the absorption bottle was washed, and the rinse solution was transferred into the colorimetric tube, and the volume was adjusted to the scale, and each of them was transferred into the headspace bottle (6.8).

Weigh 3.2 g of sodium chloride (5.4) and 1.0 g of potassium sulfate (5.5) into the headspace bottle (6.8).

10.00 ml of solution was transferred into a headspace bottle. Add 500 µl sodium hydroxide solution (5.9) and 100 µl ammonia water (5.6), immediately Seal the headspace bottle and shake gently until the salt is dissolved. When adding ammonia and sodium hydroxide solution, it should be placed on the bottom of the headspace bottle to avoid the target Loss of compounds.

7.3.2 Exhaust gas sample

Transfer the sample solution (7.1.2) in two absorption bottles into two 50 ml colorimetric tubes, and use the appropriate amount of absorption solution (5.8) Wash the inner wall of the absorption bottle, transfer the rinse solution into the colorimetric tube, make up to the mark, and transfer 10.00 ml of the absorption solution to the top.

Empty bottle (6.8). The remaining steps are the same as 7.3.1.

7.3.3 Full Procedure Blank Sample

The entire program blank (7.1.3) is prepared according to the same steps as the air sample (7.3.1) and the exhaust gas sample (7.3.2).

7.4 Preparation of laboratory blank samples

Take 10.00 ml of the same batch of absorbent solution (5.8) instead of the sample and prepare according to the same steps as the sample preparation (7.3).

8.1 Instrument Reference Conditions

8.1.1 Headspace Sampler Reference Conditions

Heating equilibration temperature. 80 °C; heating equilibration time. 30 min; sampling needle temperature. 110 °C; transmission line temperature. 115 °C;

Injection volume. 1 ml.

8.1.2 Reference conditions of gas chromatography hydrogen flame ionization detector

Inlet temperature..200 ° C; Injection method. split injection, split ratio 10. 1; column flow rate. 1.0 ml/min; program liter Temperature. 65 ° C for 5 min, rise to.200 ° C at a rate of 10 ° C/min; detector temperature. 250 ° C, hydrogen flow. 30 ml/min, Air flow. 300 ml/min, makeup air flow. 30 ml/min.

8.1.3 Reference conditions for gas chromatography nitrogen and phosphorus detectors

Inlet temperature..200 ° C; Injection method. split injection, split ratio 10. 1; column flow rate. 1.0 ml/min; program liter Temperature. 65 ° C for 5 min, rise to.200 ° C at a rate of 10 ° C/min; detector temperature. 300 ° C, hydrogen flow. 3 ml/min, Air flow. 60 ml/min, makeup air flow. 30 ml/min.

8.2 Establishment of working curve

8.2.1 Hydrogen flame ionization detector

Take an appropriate amount of trimethylamine standard solution (5.11) and dilute with an appropriate amount of absorbent solution (5.8) to prepare at least 5 concentrations.

Point standard series, the mass concentrations of trimethylamine are 0.020 mg/L, 0.050 mg/L, 0.200 mg/L, 0.500 mg/L, 1.00 mg/L (this concentration is the reference concentration), and analyzed on the machine after treatment according to 7.3. According to the instrument reference conditions (8.1) Determination. Inject the samples in descending order of concentration, with the concentration of the standard series (mg/L) as the abscissa and the corresponding the peak area of the chromatographic peak is the ordinate, and a working curve is established.

8.2.2 Nitrogen and phosphorus detector

Take an appropriate amount of trimethylamine standard solution (5.11), dilute with an appropriate amount of absorbent solution (5.8), and prepare at least 5 concentrated for the standard series of degree points, the mass concentrations of trimethylamine are 0.005 mg/L, 0.020 mg/L, 0.050 mg/L, 0.500 mg/L, 1.00 mg/L (this concentration is the reference concentration), and analyzed on the machine after treatment according to 7.3. According to the instrument reference conditions (8.1) Determination. Inject the samples in descending order of concentration, with the concentration of the standard series (mg/L) as the abscissa and the corresponding the peak area of the chromatographic peak is the ordinate, and a working curve is established.

8.2.3 Standard reference chromatogram

Under the instrument reference conditions (8.1) given in this standard, reference chromatograms containing trimethylamine are shown in Figures 3 and 4.

1-air peak; 2-ammonia; 3-methylamine (25 mg/L); 4-dimethylamine (10 mg/L); 5-ethylamine (20 mg/L); 6-trimethylamine (0.80 mg/L); 7-Diethylamine (0.80 mg/L); 8-triethylamine (0.80 mg/L).

Figure 3 Reference chromatogram with trimethylamine (hydrogen flame ionization detector)

1-air peak; 2-methylamine (25 mg/L); 3-dimethylamine (10 mg/L); 4-ethylamine (8.0 mg/L); 5-trimethylamine (0.50 mg/L); 6-Diethyl Amine (0.25 mg/L); 7-triethylamine (0.25 mg/L).

Figure 4 Reference chromatogram with trimethylamine (nitrogen and phosphorus detector)

8.3 Sample determination

Make the measurement according to the same instrument reference conditions (8.1) as the working curve.

8.4 Blank test

Perform the measurement in accordance with the same procedures as the sample measurement (8.3) and the instrument reference conditions.

9.1 Qualitative analysis

Characterize by the retention time of the target compound.

9.2 Result calculation

9.2.1 Air samples

Calculate the concentration of trimethylamine in the air sample according to formula (1).

Where. rho-the concentration of trimethylamine in the air sample, mg/m 3;

rho1- the concentration of the sample solution in the first absorption bottle, mg/L;

rho2-the concentration of the sample solution in the second absorption bottle, mg/L;

Vt-volume of sample to be tested, ml;

D-sample dilution factor;

Vs-Sampling volume in standard or reference state (298.15 K, 101.325 kPa), L.

9.2.2 Exhaust gas samples

Calculate the concentration of trimethylamine in the exhaust gas sample according to formula (2).

Where. rho-the concentration of trimethylamine in the exhaust gas sample, mg/m 3;

rho1- the concentration of the sample solution in the first absorption bottle, mg/L;

rho2-the concentration of the sample solution in the second absorption bottle, mg/L;

Vt-volume of sample to be tested, ml;

D-sample dilution factor;

Vnd-Sampling volume of dry flue gas under standard conditions, L.

9.3 Representation of results

The number of digits after the decimal point of the measurement result is consistent with the method detection limit, but a maximum of 3 significant digits is retained.

10.1 Precision

Six laboratories performed 6 parallel determinations of 3 different concentrations of spiked samples. When using a FID detector, the spiked concentrations were 0.025 mg/m3, 0.100 mg/m3, and 1.50 mg/m3, respectively.

The standard deviations are 2.9% to 8.0%, 1.1% to 7.2%, 1.3% to 6.9%, and the relative standard deviations between laboratories are 8.2%, 4.6%, 5.1%, with repeatability limits of 0.040 mg/m3, 0.014 mg/m3, and 0.13 mg/m3, respectively.

Others are 0.0071 mg/m3, 0.019 mg/m3, and 0.26 mg/m3; when the NPD detector is used, the spiked concentrations are.

0.010 mg/m

3. 0.025 mg/m3 and 1.50 mg/m3, measured after simulated sampling, the relative standard deviations in the laboratory are respectively it is 4.2% to 18%, 2.0% to 7.6%, 1.2% to 7.0%, and the relative standard deviations between laboratories are 7.9%, 7.9%, and 5.4%.

Repeatability limits are 0.0030 mg/m3, 0.0044 mg/m3, and 0.13 mg/m3, respectively. Reproducibility limits are 0.0035 mg/m3, 0.0072 mg/m 3. 0.26 mg/m3.

Six laboratories prepared standard gas samples with concentrations of 0.538 mg/m3 and 5.38 mg/m3 in six groups, respectively.

Determined after sampling. When using FID detectors, the relative standard deviations in the laboratory are 1.4% ~ 7.4% and 2.8% ~ 7.3%, the relative standard deviations between laboratories were 3.5% and 4.2%, and the repeatability limits were 0.0069 mg/m3 and 0.071 mg/m 3, the reproducibility limits are 0.0079 mg/m3 and 0.088 mg/m3 respectively; when using NPD detector, the experiment the indoor relative standard deviations were 1.7% to 11% and 2.2% to 8.8%, and the relative standard deviations between laboratories were 7.3% and 5.9%, repeatability limits are 0.0093 mg/m3 and 0.071 mg/m3, and reproducibility limits are 0.014 mg/m3 and 0.12 mg/m 3.

10.2 Accuracy

Six laboratories performed 6 parallel determinations of 3 different concentrations of spiked samples.

When the FID detector is used, the spiked concentrations are 0.025 mg/m3, 0.100 mg/m3, and 2.00 mg/m3, respectively.

After the intended sampling, the recovery of trimethylamine ranges from 96.7% to 100%, 97.3% to 105%, and 97.0% to 102%;

The final recoveries were 98.6 ± 2.8%, 101 ± 5.4%, and 98.7 ± 3.6%.

When an NPD detector is used, the spiked concentrations are 0.010 mg/m3, 0.050 mg/m3, and 2.00 mg/m3, respectively.

The range of recovery of trimethylamine after simulated sampling was 98.3% ~ 118%, 97.2% ~ 108% and 97.7% ~ 102%; the final recoveries were 104 ± 15%, 101 ± 8.0%, and 99.4 ± 3.2%.