HJ 1078-2019Stationary source emission--Determination of 8 organosulfur compounds including methanethiol--Bag sampling and preconcentration/gas chromatography mass spectrometry (English PDF)

6.8 Tank cleaning device. It can pump the tank to vacuum (7 samples

7.1 Sample collection and storage

7.1.1 Sample collection

Determination of sampling location and sampling point, sampling frequency and sampling time of exhaust gas from fixed pollution sources, measurement and sampling of exhaust parameters such operations implement the relevant provisions of HJ/T 397, GB/T 16157 and HJ 732. When sampling, heating sampling should be turned on as required for the power supply, the air bag must be cleaned with sample gas at least 3 times, and then use the sampling device (6.1) to collect the sample gas.

7.1.2 Sample storage

Airbag samples should be stored away from light at room temperature, and should be analyzed within 12 hours after sampling. If methyl mercaptan and ethyl mercaptan are not analyzed at this time, the sample can be measured within 18 h. Otherwise, use the pneumatic connector (6.12) to introduce the sample into the pre-clean and draw to the analysis was completed within 7 days in the vacuum tank (6.6).

7.2 Preparation of samples

7.2.1 Heating of the sample

Before the sample analysis, the inner wall of the sample air bag must be observed. If droplets condense, the air bag should be placed in an oven and heated Until the droplet condensation phenomenon is eliminated, then quickly analyze. If there is no droplet condensation, the air bag (6.9) or tank (6.6) Connect directly to the autosampler (6.5) for analysis.

Note. When using an oven to heat the air bag, a suitable heating temperature (not more than 50 ° C) should be set to avoid heating deformation of the sampling bag.

7.2.2 Dilution of the sample

When the concentration of sulfur-containing organic compounds in the gas sample exceeds the linear range of the standard curve, the sample needs to be diluted. Dilute when the release factor does not exceed 3, the tank (6.6) can be diluted with nitrogen (5.8). Must be measured with a vacuum pressure gauge (6.10) Set the pressure in the tank and calculate the dilution factor according to formula (1). When the dilution factor exceeds 3, a gas-tight syringe (6.11) can be used Use a plug (6.13) to inject a suitable amount of sample into a tank that has been pre-cleaned and evacuated, and then pressurize it to 101 kPa with nitrogen and calculate the dilution factor according to formula (2).

In the formula.% 00-dilution multiple, dimensionless;

Xa-tank pressure before dilution, kPa;

4Ya-diluted tank pressure, kPa.

% 00a

% 00% 00

In the formula.% 00--dilution multiple, dimensionless;

Va-the volume of the tank, ml;

V% 00-the amount of sample injected into the tank, ml.

Note. The laboratory may adopt other equivalent dilution methods.

7.3 Preparation of blank samples

7.3.1 Blank sample of the whole program

Take a sample and collect an air bag of the same batch, fill it with nitrogen in the laboratory and bring it to the sampling site without sample collection.

Follow the same steps as sample storage (7.1.2) to save the blank sample of the whole procedure and return it to the laboratory.

7.3.2 Laboratory blank samples

Take a sample and collect an air bag of the same batch, and fill it with nitrogen in the laboratory.

8.1 Instrument reference conditions

8.1.1 Reference conditions of cold trap concentrator

At room temperature, the sampling volume is 50.0 ml (can be adjusted according to actual conditions) Primary cold trap (empty tube). trapping temperature. -30 °C; trapping flow rate. 80 ml/min; analytical temperature. 10 °C; valve temperature.

120 °C; baking temperature. 150 °C; baking time. 10 min.

Secondary cold trap (TENAX tube). trapping temperature. -80 °C, transfer preheating temperature. -60 °C; trapping flow rate. 10 ml/min;

Resolution temperature. 10 ° C; valve temperature. 120 ° C; baking temperature. 190 ° C; baking time. 10 min.

Three-stage cold trap (silanized stainless steel capillary). focusing temperature. -170 °C; analysis time. 2 min; analysis temperature.

50 ~ 70 °C; baking time. 3 min.

Transmission line temperature. 100 ° C.

Note. The above conditions are the introduction of liquid nitrogen (5.9) low temperature enrichment at the same time in the first-stage cold trap. If segmented low temperature enrichment is used, when the primary cold trap is glass for beads, the trapping temperature is recommended to be adjusted to -170 °C, and the trapping temperature of the secondary cold trap can be adjusted to -30 °C or below. Different models of the best the working conditions are different, and the operation should be carried out according to the instruction manual of the instrument.

8.1.2 Reference analysis conditions of gas chromatography

Program temperature rise. the initial temperature is -35 °C, after holding for 3 minutes, the temperature was raised to 180 °C at a rate of 7.5 °C/min and kept for 3 minutes Inlet temperature. 100 ° C.

Solvent delay time. 2.7 min.

Carrier gas flow rate. the initial flow rate is 2.5 ml/min, and it is maintained at 2 ml/min for 30 min after 4 min.

5 Split ratio. 20. 1.

Note. Separation of sulfur-containing organic compounds can be accomplished by programming at an initial temperature of room temperature.

8.1.3 Reference analysis conditions for mass spectrometry

Interface temperature. 250 °C;

Ion source temperature. 230 ° C;

Ionization energy. 70eV;

Scanning method. full scan (SCAN);

Scanning range. 35 ~ 300 amu.

Note. The best working conditions of different models of instruments are different, and they should be operated according to the instruction manual of the instrument. If you meet the qualitative requirements, you can also Use Select ion scan method (SIM).

8.1.4 Instrument performance check

Before analyzing samples, you need to check the performance of the GC/MS instrument. Concentrate 4-bromofluorobenzene standard gas (5.6) through cold trap the instrument injects 50.0 ml. The BFB key ion abundance obtained must meet the criteria in Table 1.

Table 1 Key ion abundance standards for 4-bromofluorobenzene (BFB)

Mass ion abundance standard mass ion abundance standard 50 8% ~ 40% of mass 95 174 50% ~ 120% of mass 95 75 30% ~ 66% of mass 95 175 4% ~ 9% of mass 174 95 base peak, 100% relative abundance 176 mass 174 93% ~ 101% 96 5% to 9% of mass 95 177 5% to 9% of mass 176 173 is less than 2% of mass 174

8.2 Calibration

8.2.1 Standard gas preparation

Dilute the standard gas (5.1) 100 times. the standard gas (5.1) steel cylinder and nitrogen (5.8) steel cylinder and the gas dilution instrument (6.7) Connect, set the dilution factor, open the cylinder valve, adjust the flow rate of the two gases, wait for the standard gas and nitrogen flow After the speed is stabilized, empty it for more than 10 minutes to saturate the active points in the pipeline, and then take the 6 L tank (6.6) that was pre-cleaned and evacuated to vacuum Connect to the gas diluting instrument (6.7), open the tank valve and start preparation. After the tank pressure reaches the preset value (generally 172 kPa), Close the tank valve and cylinder gas valve.

8.2.2 Internal standard is prepared with gas

The internal standard uses a gas concentration of 100 nmol/mol. Prepare the internal standard gas (5.3) according to step 8.2.1.

8.2.3 Determination of calibration series

Extract 50.0 ml, 100 ml, 300 ml, 500 ml, and 700 ml standard gas (5.2), each adding 50.0 ml

6 The internal standard uses gas (5.4), and the target compound concentrations are 20 nmol/mol, 40 nmol/mol, 120 nmol/mol, Standard gas series of.200 nmol/mol and 280 nmol/mol (this is the reference concentration). According to the reference conditions of the instrument, Measure from low to high concentration.

8.2.4 Calculation of average relative response factor

The relative response factor (% 00% 00% 00% 00) of the target compound at point i of the standard series is calculated according to formula (3).

% 00% 00% 00i =

% 00% 00

% 00% 00t

×% 00% 00t

% 00i

In the formula.% 00% 00% 00i--the relative response factor of the target compound at point i in the standard series, dimensionless;

Ai--the quantitative ion peak area of the target compound at point i in the standard series;

AIS--The i-point in the standard series corresponds to the target compound to quantify the ion peak area;

% 00% 00t--the mole fraction of the internal standard compound, nmol/mol;

% 00% 00--the mole fraction of the target compound at point i in the standard series, nmol/mol.

The average relative response factor of the target is calculated according to formula (4).

% 00% 00% 00% 00% 00% 00% 00% 00 =% 00 % 00% 00% 00% 00% 00% 00 (4) where.% 00% 00% 00% 00% 00% 00% 00% 00-the average relative response factor of the target compound, dimensionless;

% 00% 00% 00% 00--the relative response factor of the target compound at point i in the standard series, dimensionless;

n--standard series points.

When calculating with relative response factors, the relative standard deviation (RSD) of the relative response factors of the standard series of target compounds should be Less than or equal to 30%.

8.2.5 Establish the calibration curve by least square method

Taking the response value ratio of the target compound and the corresponding internal standard as the ordinate, and the concentration ratio as the abscissa, the least square method is used to establish for linear calibration curves, the correlation coefficient must be greater than or equal to 0.990.

8.2.6 Total ion current (TIC)

The total ion current diagram of the target compound is shown in Figure 1. For the retention time and characteristic ions of the target compound, see Appendix B.

71-1,4-difluorobenzene (IS), 2-methyl mercaptan, 3-ethyl mercaptan, 4-methyl sulfide, 5-carbon disulfide, 6-methyl ethyl sulfide, 7-thiophene, 8-ethyl sulfide, 9-dimethyl disulfide.

Figure 1 Total ion current diagram

8.3 Determination of samples

Connect the air bag (6.9) or tank (6.6) to the autosampler (6.5), take 50.0 ml sample for analysis, and add 50.0 the internal standard for ml uses gas (5.4) and is measured according to the instrument reference conditions (8.1).

8.4 Blank test

Follow the same procedure as the sample determination to perform the full procedure blank (7.3.1) and laboratory blank (7.3.2) determination.

9.1 Qualitative analysis

Full-scan measurement, with the relative retention time of target in the sample, auxiliary qualitative ion and quantitative ion the abundance ratio is compared with the target substance in the standard substance to qualitatively. The relative retention time of the target compound in the sample and the calibration series the deviation of the relative retention time of the compound should be within ± 3.0%. Auxiliary qualifier ion and quantification of target compounds in samples Peak area ratio of ion (Q sample) to auxiliary qualitative ion and quantitative ion peak area ratio of standard series of target compounds (Q standard) the relative deviation is controlled within ± 30%.

Calculate the relative retention time RRT according to formula (5).

RRT = RTc

RTIt

In the formula. RRT--the relative retention time of the target compound, dimensionless;

RTc--retention time of target compound, min;

8RTIS--Retention time of internal standard, min.

Calculate the average relative retention time (RRT) according to formula (6). the relative retention of the same target compound in the standard series Time average.

RRT% 00% 00% 00% 00% 00 = i nRRTi% 00 (6) in the formula. RRT% 00% 00% 00% 00% 00--the average relative retention time of the target object, dimensionless;

RRTi--the relative retention time of the i-th target in the standard series, dimensionless;

n--standard series points.

Calculate the peak area ratio of auxiliary qualitative ion and quantitative ion according to formula (7).

In the formula. Q--Auxiliary qualitative ion and quantitative ion peak area ratio;

Aq--Auxiliary qualitative ion peak area;

At--quantitative ion peak area.

9.2 Quantitative analysis

The content of the target substance (mg/m3) in the sample is calculated according to formula (8).

rho =% 00 ×

22.4

In the formula. rho--the mass concentration of the target in the sample, mg/m3 % 00--the mole fraction of the target calculated by the calibration curve, nmol/mol;

M--the molar mass of the target, g/mol, see Appendix B;

D--Dilution multiple, dimensionless;

22.4--Molar volume of gas in standard state (273.15 K, 101.325 kPa), L/mol.

9.3 Results

The number of digits after the decimal point of the measurement result is consistent with the detection limit of the method, and at most three significant digits are retained.

10.1 Precision

The six laboratories carried out precision tests on blank spiked samples with concentrations of approximately 0.05 mg/m3, 0.20 mg/m3, and 0.30 mg/m3, respectively.

For density determination, the relative standard deviation in the laboratory ranges from 0.5% to 15%, 0.6% to 6.9%, 0.3% to 7.1%;

The relative standard deviations between laboratories are 6.4% to 19%, 4.9% to 13%, 5.5% to 9.3%; the reproducibility limits are respectively 0.01 mg/m3, 0.02 to 0.03 mg/m3, 0.02 to 0.04 mg/m3, and the reproducibility limits are 0.02 to 0.03 mg/m3, 0.04 ~ 0.09 mg/m3, 0.06 ~ 0.09 mg/m3. See Appendix C.

10.2 Accuracy

The six laboratories have exhaust gas samples from chemical companies with spiked concentrations of approximately 0.10 mg/m3, 0.30 mg/m3 and 0.50 mg/m3.

The recovery rate of the spiked samples was repeated 6 times for 9 products. The spiked recovery ranges were. 87.6% ~ 107%, 103% ~ 108%, 101% ~ 109%. See Appendix C for details.

11.1 Laboratory blank

Every 20 samples or each batch (less than 20 samples/batch) should analyze at least one laboratory blank.

The concentration of the target compound should be below the detection limit of the method.

11.2 Blank

Every 20 samples or each batch (less than 20 samples/batch) should analyze at least one full program blank.

The concentration of the target compound should be below the detection limit of the method.

11.3 Internal standard

The retention time of the internal standard in the sample is different from the retention time of the internal standard in the continuous calibration of the day or the calibration curve drawn recently.

Should not exceed 20 s, quantitative ion peak area change should be between 60% to 140%.

11.4 Continuous calibration

The middle concentration point of the calibration curve is analyzed every 24 h. The relative error between the measurement result and the standard value should be less than or equal to 30%, Otherwise, you should find the cause or redraw the stand...