Detail of HJ 759-2015

Introduction of HJ 759-2015

1 Applicable Scope This standard specifies the determination of volatile organic compounds in ambient air collected by specially-prepared canisters and analyzed by gas chromatography/mass spectrometry. This standard is applicable to the determination of 67 volatile organic compounds in ambient air, e.g., propylene. Other volatile organic compounds may also be determined according to this standard if this method is verified to be applicable. Where the sampling volume is 400 ml, the detection limit of this method in full scan mode is 0.2 μg/m3 to 2 μg/m3, and the lower limit of determination is 0.8 μg/m3 to 8.0 μg/m3, see Annex A for details. 2 Normative References This standard refers to the following documents or the provisions therein. For undated references, the effective version is applicable to this standard. HJ/T 194 Technical Specifications on Manual Methods for Ambient Air Quality Monitoring 3 Principle Collect the ambient air sample by a stainless steel canister with deactivated inner wall, subject the sample to cold trap concentration, thermal desorption and gas chromatography separation, and test with mass spectrometry detector. Perform qualitative determination through comparison with standard mass spectrogram and retention time, and quantitative determination through internal standard method. 4 Reagents and Materials 4.1 Standard gas: with a concentration of 1 μmol/mol. It is stored in a high-pressure cylinder with pressure no less than 1.0 MPa for 1 year (or refer to the relevant instructions in the certificate of standard gas). Certified standard gas may be purchased or appropriate mixed standard gas may be customized by a qualified organization according to the requirements of actual practice. 4.2 Standard gas for use: dilute the standard gas (4.1) with high-purity nitrogen (4.8) to 10 nmol/mol in the gas dilution device (5.6) and preserve for 20d. 4.3 Internal standard gas (certified standard substance): composed of bromochloromethane, 1,2-difluorobenzene and chlorobenzene-d5, with a concentration of 1 μmol/mol. It is stored in a high-pressure cylinder with pressure no less than 1.0 MPa for 1 year (or refer to the relevant instructions in the certificate of standard gas). The above-mentioned one to three internal standard substances are recommended to be used in this standard and other substances may also be used as internal standard substance. 4.4 Internal standard gas for use: dilute the internal standard gas (4.3) with high-purity nitrogen (4.8) to 100 nmol/mol in the gas dilution device (5.6) and preserve for 20d at maximum. 4.5 BFB standard gas: with a concentration of 1 μmol/mol. It is stored in a high-pressure cylinder with pressure no less than 1.0 MPa by mixing with the internal standard gas (4.3) for 1 year (or refer to the relevant instructions in the certificate of standard gas). 4.6 BFB standard gas for use: dilute the BFB standard gas (4.5) with high-purity nitrogen (4.8) to 100 nmol/mol in the gas dilution device (5.6) and preserve for 20d at maximum. 4.7 Helium: ≥99.999%. 4.8 High-purity nitrogen: ≥99.999%, with hydrocarbon removal device. 4.9 High-purity air: ≥99.999%, with hydrocarbon removal device. 4.10 Liquid nitrogen. 5 Instruments and Apparatus

Contents of HJ 759-2015

Foreword iii 1 Applicable Scope 2 Normative References 3 Principle 4 Reagents and Materials 5 Instruments and Apparatus 6 Sample 7 Analysis Procedure 8 Calculation and Expression of Results 9 Precision and Accuracy 10 Quality Assurance and Quality Control 11 Precautions Annex A (Normative) Method Detection Limit and Lower Limit of Determination Annex B (Informative) Method Precision and Accuracy Annex C (Informative) Corresponding Relationship between Internal Standard Substances and Target Compounds Annex D (Informative) Total Ion Chromatography of Volatile Organic Compounds