HJ 1220-2021 English PDF

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HJ 1220-2021: Ambient air - Determination of 6 volatile carboxylic acid compounds - Gas chromatography-mass spectrometry
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Basic data

Standard ID: HJ 1220-2021 (HJ1220-2021)
Description (Translated English): Ambient air - Determination of 6 volatile carboxylic acid compounds - Gas chromatography-mass spectrometry
Sector / Industry: Environmental Protection Industry Standard
Word Count Estimation: 14,146
Issuing agency(ies): Ministry of Ecology and Environment

HJ 1220-2021: Ambient air - Determination of 6 volatile carboxylic acid compounds - Gas chromatography-mass spectrometry

---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
(Ambient air - Determination of six volatile carboxylic acid compounds - Gas chromatography-mass spectrometry) National Ecological Environment Standard of the People's Republic of China 6 kinds of volatile carboxylic acid compounds in ambient air Determination gas chromatography-mass spectrometry Ambient air-Determination of 6 volatile carboxylic acid compounds -Gas chromatography-mass spectrometry This electronic version is the official standard text, which is reviewed and typeset by the Environmental Standards Institute of the Ministry of Ecology and Environment. Published on 2021-12-16 2022-06-01 Implementation Released by the Ministry of Ecology and Environment directory Foreword...ii 1 Scope...1 2 Normative references...1 3 Principles of the method...1 4 Reagents and materials...1 5 Instruments and equipment...2 6 Samples...3 7 Analysis steps...4 8 Result calculation and representation...6 9 Accuracy...7 10 Quality Assurance and Quality Control...8 11 Waste Disposal...8 Appendix A (normative appendix) detection limit and lower limit of determination of the method...9 Appendix B (informative) Accuracy of the method...10 Determination of Six Volatile Carboxylic Acid Compounds in Ambient Air by Gas Chromatography-Mass Spectrometry Warning. The methyl tert-butyl ether used in the experiment has certain toxicity. The standard solution preparation and sample pretreatment process should be carried out in a fume hood. When operating, wear protective equipment as required to avoid inhalation or contact with skin and clothing.

1 Scope of application

This standard specifies the gas chromatography-mass spectrometry method for the determination of six volatile carboxylic acid compounds in ambient air. This standard applies to acetic acid, propionic acid, n-butyric acid, acrylic acid, isovaleric acid and n-valeric acid in ambient air and fugitive emission monitoring points in the air Determination of 6 kinds of volatile carboxylic acid compounds. When the sampling volume is 60 L (in the standard state) and the concentration volume is 1.0 ml, the detection limit of the method is 0.2 μg/m3～7 μg/m3, The lower limit of determination is 0.8 µg/m3 to 28 µg/m3.See Appendix A for details.

2 Normative references

This standard refers to the following documents or clauses thereof. For dated references, only the dated version applies to this standard. For undated references, the latest edition (including all amendments) applies to this standard. HJ/T 55 Technical guidelines for monitoring fugitive emissions of air pollutants HJ 194 Technical Specification for Manual Monitoring of Ambient Air Quality

3 Principles of the method

The volatile carboxylic acid compounds in ambient air and the air of fugitive emission monitoring points are enriched by impregnated silica gel adsorbent, and then absorbed by water. The desorbed liquid was extracted with methyl tert-butyl ether, concentrated and fixed to volume, separated by gas chromatography, and detected by mass spectrometry. According to retention time, characteristic ion mass charge The ratio and its abundance ratio were qualitative, and the internal standard method was used for quantification.

4 Reagents and Materials

Unless otherwise specified, analytical reagents that meet national standards are used in the analysis, and the experimental water is pure water without target substances. 4.1 Sodium chloride (NaCl). calcined at 400 ℃ for 4 h before use, sealed and stored in a ground glass bottle after cooling. 4.2 Sodium carbonate (Na2CO3). dry at 105 °C for 2 h before use, and store in a desiccator. 4.3 Methyl tert-butyl ether (CH3OC(CH3)3). chromatographically pure. 4.4 Sulfuric acid (H2SO4). ρ=1.84 g/ml. 4.5 Sodium carbonate solution. ρ(Na2CO3)=10.6 g/L. Weigh 10.6 g of sodium carbonate (4.2), dissolve in water, and dilute to 1000 ml. 4.6 Sulfuric acid solution. c(H2SO4)=0.5 mol/L. Take 27.2 ml of sulfuric acid (4.4) and slowly pour it into a small amount of water and dilute to 1000 ml. 4.7 Acetic acid (CH3COOH) standard. purity ≥99.5%. 4.8 Standard product of propionic acid (C2H5COOH). purity ≥99.5%. 4.9 Acrylic acid (C2H3COOH) standard. purity ≥99.5%. 4.10 Standard product of n-butyric acid (C3H7COOH). purity ≥99.5%. 4.11 Isovaleric acid (C4H9COOH) standard. purity ≥98.5%. 4.12 Standard product of n-valeric acid (C4H9COOH). purity ≥99%. 4.13 Standard product of n-valeric acid-d9 (C4H9COOH-d9). purity ≥98%. 4.14 Standard stock solution of carboxylic acid. ρ(CH3COOH)=20.0 g/L, ρ(C2H5COOH)=8.00 g/L, ρ(C2H3COOH)=4.00 g/L, ρ(C3H7COOH)=1.00 g/L, ρ(C4H9COOH)=1.00 g/L. Weigh out 2.00 g acetic acid standard (4.7), 0.80 g propionic acid standard (4.8), 0.40 g acrylic acid standard (4.9), 0.10 g n-butyric acid standard (4.10), 0.10 g isovaleric acid standard (4.11) and 0.10 g n-valeric acid standard (4.12) (all accurate to 0.1 mg) In a 100 ml volumetric flask, dilute to the mark with methyl tert-butyl ether (4.3), and shake well. Refrigerated below 4 ℃, can be stored for 1 month. Or use commercially available certified standard solutions. 4.15 Standard solution of carboxylic acid. ρ(CH3COOH)=60.0 mg/L, ρ(C2H5COOH)=24.0 mg/L, ρ(C2H3COOH)=12.0 mg/L, ρ(C3H7COOH)=3.00 mg/L, ρ(C4H9COOH)=3.00 mg/L. Pipette an appropriate amount of carboxylic acid standard stock solution (4.14) and dilute it with methyl tert-butyl ether (4.3). Ready to use. 4.16 Internal standard stock solution. ρ=10.0 g/L. Weigh 100 mg (accurate to 0.1 mg) of n-valeric acid-d9 standard (4.13) in a 10 ml volumetric flask, use methyl tert-butyl ether (4.3) Dilute to the mark and shake well. Refrigerated below 4 ℃, can be stored for 1 month. Or use commercially available certified standard solutions. 4.17 Internal standard solution. ρ=200 mg/L. Pipette an appropriate amount of internal standard stock solution (4.16) and dilute with methyl tert-butyl ether (4.3). Refrigerated below 4 ℃, can be stored for 1 month. 4.18 Impregnated silica gel. Silica gel with a particle size of 380 µm to 830 µm (40 mesh to 20 mesh) is soaked in sodium carbonate solution (4.5) for 30 minutes, Pour off the solution and let it dry. 4.19 Impregnated silicone sampling tube. a glass tube with a length of 15 cm, an outer diameter of 6 mm and an inner diameter of 4 mm, with two sections of impregnated silica gel inside, of which section A 450 mg, B section 150 mg, the two ends of the sampling tube and between the two sections of impregnated silica gel are filled with silanized glass wool, and the two ends are sealed after filling. or buy Buy commercially available sampling tubes. The schematic diagram of the sampling tube is shown in Figure 1.

5 Instruments and equipment

5.1 Air sampler. with flow control function, the flow range is 0.1 L/min ~ 1.0 L/min, other technical indicators should comply with HJ 194 Provisions. 5.2 Gas chromatography-mass spectrometer. The gas chromatography part has a capillary column and a split/splitless inlet, and the temperature can be programmed. mass spectrometer There are electron impact (EI) ion source, full scan/selected ion scan, automatic/manual tuning, spectral library search and other functions. 5.3 Chromatographic column. 30 m × 0.25 mm × 0.25 µm, the stationary phase is polyethylene glycol modified with nitroterephthalic acid, or other equivalent chromatography column. 5.4 Ultrasonic cleaner. power ≥.200 W. 5.5 Nitrogen blower. 5.6 Sample tube. glass or polyperfluoroethylene propylene and other materials, 10 ml, with stopper. 5.7 Analytical balance. the actual division value is 0.1 mg. 5.8 Common laboratory instruments and equipment.

6 samples

6.1 Sample Collection 6.1.1 Ambient air and fugitive emission monitoring point air samples The layout and sampling of ambient air sampling points conform to the requirements of HJ 194, and the layout and sampling of fugitive emission monitoring points conform to HJ/T 55 relevant provisions in. When sampling, open both ends of the impregnated silicone sampling tube (4.19), and connect the B end of the sampling tube to the air inlet of the air sampler (5.1) to 0.5 L/min ~ 1.0 L/min flow sampling, the sampling volume is 60 L. Seal both ends with sealing caps immediately after sampling. 6.1.2 Field blank samples Bring the same batch of impregnated silicone sampling tube (4.19) to the sampling site, open its two ends, do not connect it with the sampler, and seal it with a sealing cap immediately. Both ends are sealed, stored in the same way as the sample, and shipped back to the laboratory with the sample. 6.2 Storage of samples After the sample is collected, it should be stored in a sealed place below 4 °C and protected from light, and it should be analyzed as soon as possible; if it cannot be analyzed in time, the sample analysis should be completed within 5 days. Preparation, the prepared samples should be tested within 15 days. 6.3 Preparation of samples 6.3.1 Sample extraction Transfer the impregnated silica gel of section A and section B of the sampling tube into the corresponding sample tube (5.6) respectively, and carry out the following treatments respectively. add 5.0 ml of water, Put it in an ultrasonic cleaner (5.4), and after sonicating for 20 min below room temperature, pipette 3.0 ml of the extract to another sample tube (5.6). 6.3.2 Sample extraction Add 1.2 g of sodium chloride (4.1) to the extract (6.3.1), shake well, adjust the pH to ≤4 with sulfuric acid solution (4.6), add Extract with 3.0 ml methyl tert-butyl ether (4.3), shake well and let stand, and collect the upper extract. Repeat the extraction 2 more times and combine the extracts. 6.3.3 Sample concentration Concentrate the extract (6.3.2) to slightly less than 1.0 ml with a nitrogen blower (5.5), add 10 μl of the internal standard solution (4.17), use methyl tertiary Dilute to 1.0 ml with butyl ether (4.3), to be tested. 6.4 Preparation of blank samples 6.4.1 Laboratory Blanks Prepare a laboratory blank sample with the same batch of sampling tubes as the sample preparation (6.3). 6.4.2 Field blank The field blank sample (6.1.2) is prepared according to the same procedure as the sample preparation (6.3).

7 Analysis steps

7.1 Instrument reference conditions 7.1.1 Gas chromatography reference conditions Injection port temperature. 250 °C; injection method. splitless injection; injection volume. 1.0 µl; carrier gas. helium (4.21); column flow rate. 1.5 ml/min; column temperature program. 50 °C (hold for 2 min), increase the temperature at 8 °C/min to 150 °C, and then increase the temperature at 20 °C/min to 220 °C (hold for 5 min). 7.1.2 Reference conditions for mass spectrometry Ion source temperature. 230 °C; transfer line temperature. 240 °C; ionization mode. EI; ionization energy. 70 eV; scan mode. optional Selective Ion Scanning (SIM). The reference retention time, quantitative and qualifier ions of each target are shown in Table 1. 7.2 Calibration 7.2.1 Establishment of calibration curve Take appropriate amount of carboxylic acid standard solution (4.15) and internal standard solution (4.17) respectively, and prepare 6 concentrations with methyl tert-butyl ether (4.3). Calibration series of points. The reference concentrations of the calibration series are shown in Table 2. According to the instrument reference conditions (7.1), analyze and measure from low concentration to high concentration. Take the target concentration as the abscissa, take the target The product of the ratio of the quantitative ion response values of the internal standard substance and the internal standard substance and the concentration of the internal standard substance is the ordinate, and a calibration curve is established. 7.3 Sample Determination The determination of the sample (6.3) is carried out under the same conditions as the establishment of the calibration curve (7.2.1). 7.4 Blank test Carry out the measurement of the blank sample (6.4) under the same conditions as the sample measurement (7.3).

8 Result calculation and representation

8.1 Qualitative Analysis By comparing the retention time, characteristic ion mass-to-charge ratio and its abundance ratio of the target in the sample and the target in the calibration series, the The target is characterized. The relative retention time of the target in the sample (the ratio of target retention time to internal standard retention time) is compared with that in the calibration series The difference between the relative retention times of this compound should be within ±0.03.The phase of the qualifier ion relative to the quantifier ion of the target in the sample Comparing the relative abundance of the compound with the intermediate point of the calibration series, the relative deviation should be within ±30%. 8.2 Quantitative analysis 8.2.1 Calculation of the concentration of the target substance in the sample 8.2.1.1 Calculation with Average Relative Response Factor The mass concentration () of the target substance in the sample is calculated according to formula (5). 8.2.1.2 Calculation with calibration curve The mass concentration () of the target substance in the sample is calculated from the corresponding calibration curve. 8.2.2 Result calculation The mass concentration (ρ) of the target substance in the sample is calculated according to formula (6). 8.3 Result representation The number of decimal places in the determination result should be consistent with the detection limit, and should not exceed 3 significant figures.

9 Accuracy

9.1 Precision The 6 laboratories added standard amounts of 0.025 µg to 1.0 µg, 0.5 µg to 5.0 µg, and 3.6 µg to 36 µg (equivalent to air samples), respectively. The samples of 0.4 µg/m3～17 µg/m3, 8.3 µg/m3～83 µg/m3, 60.0 µg/m3～600 µg/m3) were repeatedly determined for 6 times. The relative standard deviations in the laboratory are. 4.2%-15%, 1.9%-12%, 1.9%-11%; The relative standard deviations among laboratories are. 3.7%-15%, 6.6%-10%, 2.7%-10%; The repeatability limits are. 0.1 µg/m3～4 µg/m3, 0.9 µg/m3～10 µg/m3, 9.0 µg/m3～89 µg/m3; The reproducibility limits are. 0.1 µg/m3～6 µg/m3, 1.7 µg/m3～15 µg/m3, 13 µg/m3～1.6×102 µg/m3. For method precision data, see Table B.1 in Appendix B. 9.2 Correctness The 6 laboratories carried out 6 repeated standard addition determinations on the actual air samples respectively, and the target addition amount was 0.025 µg to 12 µg (equivalent to 12 µg). 0.4 µg/m3～200 µg/m3 for air samples), the recovery rate of standard addition ranged from 61.3% to 109%, and the final recovery rate of standard addition was 69.2%±18.6%～94.8%±26%. See Table B.2 in Appendix B for method correctness data. 10 Quality Assurance and Quality Control 10.1 A blank test should be carried out before analyzing the samples. At least 1 laboratory blank should be analyzed for every 20 or batch (≤20/batch) samples and field blank samples. The measurement result of blank sample should be lower than the lower limit of method determination. 10.2 The RSD of the relative response factor of the calibration series targets should be ≤20%, or the correlation coefficient of the calibration curve should be ≥0.995.every 20 or every Batch (≤20/batch) samples should be analyzed at the middle point of the calibration curve, and the relative error between the measurement result and the concentration at this point should be within ±20%. 10.3 Every 20 samples or each batch (≤20 samples/batch) should measure 1 blank spike (add the blank silica gel to the sample tube with a micro-syringe) Quantitative carboxylic acid standard solution), the recovery rate of acetic acid is between 45% and 120%, and the recovery rate of other carboxylic acids is between 60% and 120%. 10.4 The concentration of the target substance in the B section of the sampling tube should be less than 10% of the target substance concentration in the A section, otherwise the sample should be re-collected. 11 Waste Disposal The waste liquid and waste generated in the experiment should be collected by classification, marked accordingly, and entrusted to a qualified unit for disposal according to law. ......

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