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1、Reference number ISO 14965:2000(E) ISO 2000 INTERNATIONAL STANDARD ISO 14965 First edition 2000-03-15 Air quality Determination of total non- methane organic compounds Cryogenic preconcentration and direct flame ionization detection method Qualit de lair Dosage des composs organiques non mthaniques
2、totaux Mthode par prconcentration cryognique et ionisation slective directe dans la flamme ISO 14965:2000(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which
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5、t a problem relating to it is found, please inform the Central Secretariat at the address given below. ISO 2000 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and
6、 microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 ? CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 734 10 79 E-mail copyrightiso.ch Web www.iso.ch Printed in Switzerland ii IS
7、O 2000 All rights reserved ISO 14965:2000(E) ISO 2000 All rights reservediii ContentsPage Foreword.iv Introduction.v 1Scope 1 2Normative references1 3Terms and definitions .2 4Description of the method2 4.1Sampling.2 4.2Analysis2 5Interferences 3 6Apparatus.3 6.1Sample collection system (Figure 1)3
8、6.2Sample-canister cleaning system (Figure 2).4 6.3Analytical system (Figure 3)6 7Reagents and materials 9 8Canister cleanup and preparation9 9Sampling.10 9.1General10 9.2Sample collection 11 10Sample analysis.12 10.1Assembly12 10.2Analytical system leak check.12 10.3Sample volume determination12 10
9、.4Analytical system dynamic calibration .13 10.5Analysis procedure (see Figure 3)14 11Performance criteria and Quality Assurance16 11.1General16 11.2Standard operating procedure (SOP)17 11.3Method sensitivity, accuracy and precision.17 12Method modification18 12.1Sample metering system 18 12.2Canist
10、er cleaning.18 12.3FID system18 12.4Range18 12.5Alternative cryogenic trapping and heating systems18 12.6Sub-atmospheric pressure canister sampling .18 12.7Alternative sampling system18 13Precision and accuracy.19 13.1Precision.19 13.2Accuracy.19 Annex A (informative) Example of pressurized canister
11、 Sampling Data Sheet20 Bibliography21 -,-,- ISO 14965:2000(E) iv ISO 2000 All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carrie
12、d out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. IS
13、O collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committ
14、ees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO
15、 shall not be held responsible for identifying any or all such patent rights. International Standard ISO 14965 was prepared by Technical Committee ISO/TC 146,Air quality, Subcommittee SC 3,Ambient atmospheres. Annex A of this International Standard is for information only. ISO 14965:2000(E) ISO 2000
16、 All rights reservedv Introduction Accurate measurements of ambient concentrations of total non-methane volatile organic compounds (NMVOC) are important for the control of photochemical smog because these organic compounds are primary precursors of atmospheric ozone and other oxidants. The NMVOC con
17、centrations typically found at urban sites may range up to 1 ppmC to 3 ppmC (see definition 3.4) or higher. In order to determine transport of precursors into an area, measurement of NMVOC upwind of the area may be necessary. Rural NMVOC concentrations originating from areas free from NMVOC sources
18、are likely to measure less than a few tenths of 1 ppmC. Conventional methods that depend on gas chromatography and qualitative and quantitative species evaluation are excessively difficult and expensive to operate and maintain. The method described in this International Standard involves a simple, c
19、ryogenic preconcentration procedure with subsequent direct detection with the flame ionization detector (FID). The method is sensitive and provides accurate measurements of ambient total NMVOC concentrations where species data are not required. This International Standard is intended for analysis of
20、 air samples from sampling canisters and has not been designed for continuous ambient air monitoring. Another application of this International Standard is the monitoring of the cleanliness of canisters and screening of canister samples prior to analysis. Collection of ambient air samples in pressur
21、ized canisters provides the following advantages: ?convenient integration of ambient samples over a specific time period; ?capability of remote sampling with subsequent central laboratory analysis; ?ability to ship and store samples, if necessary; ?analysis of samples from multiple sites with one an
22、alytical system; ?collection of replicate samples for assessment of measurement precision; ?specific hydrocarbon analysis may be performed with the same sample system. -,-,- INTERNATIONAL STANDARDISO 14965:2000(E) ISO 2000 All rights reserved1 Air quality Determination of total non-methane organic c
23、ompounds Cryogenic preconcentration and direct flame ionization detection method 1Scope This International Standard describes a procedure for sampling and determining concentrations of total non- methane volatile organic compounds (NMVOC) in the ambient atmosphere. This International Standard descri
24、bes the collection of cumulative samples in passivated stainless steel canisters and subsequent laboratory analysis. It describes a procedure for sampling in canisters at final pressures above atmospheric pressure (referred to as pressurized sampling). It employs a cryogenic trapping procedure for c
25、oncentration of the NMVOC prior to analysis. This International Standard describes the determination of the NMVOC by simple flame ionization detection (FID), without the gas chromatographic columns and complex procedures necessary for species separation. This International Standard is applicable to
26、carbon concentrations in the range from 20 ppbC to 10 000 ppbC. See 12.4 for procedures for lowering the range. Several variations to the method described in this International Standard are also possible; see clause 12. 2Normative references The following normative documents contain provisions which
27、, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possi
28、bility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO/TR 4227:1989,Planning of ambient
29、 air quality monitoring. ISO 6141:2000,Gas analysis Requirements for certificates for gases and gas mixtures. ISO 6145-1:1986,Gas analysis Preparation of calibration gas mixtures Dynamic volumetric methods Part 1: Methods of calibration. ISO 6145-3:1986,Gas analysis Preparation of calibration gas mi
30、xtures Dynamic volumetric methods Part 3: Periodic injections into a flowing gas stream. ISO 6145-4:1986,Gas analysis Preparation of calibration gas mixtures Dynamic volumetric methods Part 4: Continuous injection methods. ISO 6145-6:1986,Gas analysis Preparation of calibration gas mixtures Dynamic
31、volumetric methods Part 6: Sonic orifices. ISO 14965:2000(E) 2 ISO 2000 All rights reserved 3Terms and definitions For the purposes of this International Standard, the following terms and definitions apply. 3.1 cryogen refrigerant used to obtain very low temperatures in the cryogenic traps of the an
32、alytical system NOTELiquid argon (boiling point, 87 K, at standard atmospheric pressure) is recommended for the method described in this International Standard. 3.2 dynamic calibration calibration of an analytical system with pollutant concentrations that are generated in a dynamic, flowing system N
33、OTEAn example of such a system is the quantitative, flowrate dilution of a high-concentration gas standard with zero gas. 3.3 total non-methane volatile organic compounds: those compounds measured by a flame ionization detector, excluding methane, and compounds with vapour pressure above 10-2kPa, re
34、covered from the canister 3.4 parts per million billion of organic carbon ppmC ppbC concentration unit, as detected by the FID, equivalent to parts per million billion by volume multiplied by the number of carbon atoms in the calibration gas molecule NOTEDuring calibration with propane, for example,
35、 it is equivalent to parts per million by volume (ppm) or parts per billion by volume (ppb), multiplied by three. 4Description of the method 4.1Sampling An air sample is extracted directly from the ambient air, collected into a precleaned sample canister, and transported to a laboratory for analysis
36、. 4.2Analysis A fixed-volume portion of the sample air is drawn from the canister at a low flowrate through a glass-bead-filled trap that is cooled to approximately 87 K with liquid argon. The cryogenic trap simultaneously collects and concentrates the NMVOC, while allowing the nitrogen, oxygen, met
37、hane and other compounds to pass through the trap without retention. The system is dynamically calibrated so that the volume of sample passing through the trap does not have to be quantitatively measured, but shall be precisely repeatable between the calibration and the analytical phases. After the
38、fixed-volume air sample has been drawn through the trap, a helium carrier-gas flow is diverted to pass through the trap, in the opposite direction to the sample flow, and into an FID. When the residual air and methane have been flushed from the trap and the FID baseline restabilizes, the cryogen is
39、removed and the temperature of the trap is raised to 353 K to 363 K. The organic compounds previously collected in the trap revolatilize due to the increase in temperature and are carried into the FID, resulting in a response peak or peaks from the FID. The area of the peak or peaks is integrated, a
40、nd the integrated value is translated to concentration units via a previously obtained calibration curve relating integrated peak areas with known concentrations of propane. -,-,- ISO 14965:2000(E) ISO 2000 All rights reserved3 The cryogenic trap simultaneously concentrates the NMVOC while separatin
41、g and removing the methane from air samples. The technique is thus direct-reading via FID for NMVOC and, because of the concentration step, it is more sensitive than conventional continuous NMVOC analysers. The sample is injected into the hydrogen-rich flame of the FID where the organic vapors burn
42、producing ionized molecular fragments. The resulting ion fragments are then collected and detected. Because this method employs a helium carrier gas, the detector response is nearly unity for all hydrocarbon compounds. Thus, the historical short- coming of varying FID response to aromatic, olefinic
43、and paraffinic hydrocarbons is minimized. The FID is much less sensitive to most organic compounds containing functional groups such as carbonyls, alcohols, halocarbons, etc. This International Standard may yield less accurate results for some halogenated or oxygenated hydrocarbons emitted from near
44、by sources of industrial air pollutants. 5Interferences In laboratory evaluations, moisture has been found to cause a positive shift in the FID baseline. The effect of this shift is minimized by carefully selecting the integration termination point and adjusting the baseline used for calculating the
45、 area of the NMVOC peaks. When using helium as a carrier gas, FID response is quite uniform for most hydrocarbon compounds, but the response may vary considerably for other types of organic compounds. 6Apparatus 6.1Sample collection system (Figure 1) 6.1.1Sample canisters. Stainless steel electropol
46、ished vessels of 4 l to 6 l capacity, used for automatic collection of integrated field air sample. Each canister shall be stamped on its frame with a unique identification number. 6.1.2Sample pump. Stainless steel, metal bellows type, capable of at least 200 kPa maximum pressure. Ensure that pump i
47、s free of leaks, and uncontaminated by oil or organic compounds. Shock-mount the pump to minimize vibration. 6.1.3Vacuum/pressure gauge, covering the range 0 kPa to 210 kPa. 6.1.4Solenoid valve, to control the sample flow to the canister with negligible temperature rise. 6.1.5Flowrate control device
48、, e.g. mass flowmeter, of critical orifice or short capillary, to maintain the sample flowrate over the sample period. 6.1.6Particulate matter filter. Inert in-line filter, of pore size 2 ?m or less, or other suitable filter, used to filter the air sample. 6.1.7Auxiliary vacuum pump or blower, capab
49、le of drawing sample air through the sample inlet line to reduce inlet residence time to no greater than 10 s. 6.1.8Timer, programmable and electrically connected to the solenoid valve and pumps, capable of controlling the pumps and the solenoid valve. 6.1.9Sample inlet line, consisting of stainless steel tubing components, to transport the sample air into the sample system. ISO 1