Significance and Use
5.1 VOCs are emitted into ambient, indoor, and workplace air from many different sources. These VOCs are of interest for a variety of reasons including participation in atmospheric chemistry and contributing to air toxics with their associated acute or chronic health impacts.
5.2 Canisters are particularly well suited for the collection and analysis of very volatile and volatile organic compounds because they collect whole gas samples.
5.3 Chemically stable selected VOCs have been successfully collected in passivated stainless steel canisters. Collection of atmospheric samples in canisters provides for: (1) convenient integration of air samples over a specific time period (for example, 8 to 24 h), (2) remote sampling and central laboratory analysis, (3) ease of storing and shipping samples, (4) unattended sample collection, (5) analysis of samples from multiple sites with one analytical system, (6) dilution or additional sample concentration to keep the sample size introduced into the analytical instrument within the calibration range, (7) collection of sufficient sample volume to allow assessment of measurement precision through replicate analyses of the same sample by one or several analytical systems, (8) sample collection using a vacuum regulator flow controller if electricity is not available, and (9) grab sample collection for survey or screening purposes.
5.4 Interior surfaces of the canisters may be treated by any of several proprietary passivation processes including an electropolishing process to remove or cover reactive metal sites on the interior surface of the vessel and a fused silica coating process.
5.5 For this test method, VOCs are defined as organic compounds that can be quantitatively recovered from the canisters having a vapor pressure greater than 10-2 kPa at 25ºC (see Table 1 for examples).
5.6 Target compound polarity is also a factor in compound recovery. Aliphatic and aromatic hydrocarbons from C1 to C13 have been successfully measured with this test method but are not listed in Table 1 (21). Higher polarity target compounds may interact with the canister surface or humidity on the canister surface causing their apparent vapor pressure to decrease. Polar VOCs such as ethers and esters have been successfully measured by this test method and are listed in Table 1.
5.7 Recovery studies shall be conducted on VOCs not listed in Table 1 before expanding the use of this test method to include these additional compounds. Recovery from humidified spiked canisters shall agree with the spiked amount by ±30 %. The laboratory shall be responsible for verifying the relevant method performance characteristics for each compound added to the analyte list as agreed with their customer(s). The laboratory shall retain records of verification and make them available to customers upon request. Added VOCs (that is, those not listed in Table 1) shall be clearly identified in customer reports
Scope
1.1 This test method describes a procedure for sampling and analysis of selected volatile organic compounds (VOCs) in ambient, indoor, and workplace atmospheres. The test method is based on the collection of whole air samples in stainless steel canisters with specially treated (passivated) interior surfaces.
1.2 For sample analysis, a portion of the sample is subsequently removed from the canister and the collected VOCs are selectively concentrated by adsorption or condensation onto a trap, subsequently released by thermal desorption, separated by gas chromatography, and measured by a low resolution mass spectrometric detector. This test method describes procedures for sampling into canisters to final pressures both above and below atmospheric pressure (respectively referred to as pressurized and subatmospheric pressure sampling).2
1.3 This test method is applicable to specific VOCs that have been determined to be stable when stored in canisters (see Table 1). Numerous compounds, many of which are chlorinated VOCs, have been successfully tested for storage stability in pressurized canisters (1-4).3 Information on storage stability is also available for polar compounds (5-7). This test method has been documented for the compounds listed in Table 1 and performance results apply only to those compounds. A laboratory may determine other VOCs by this test method after completion of verification studies that include measurement of recovery as specified in 5.7 and that are as extensive as required to meet the performance needs of the customer and the given application.
1.4 The procedure for collecting the sample involves the use of inlet lines, air filters, flow rate regulators for obtaining time-integrated samples, and in the case of pressurized samples, an air pump. Typical long-term fixed location canister samplers have been designed to automatically start and stop the sample collection process using electronically actuated valves and timers (8-10). Temporary or short-term canister samplers may require the user to manually start and stop sample collection. A weatherproof shelter may be required if the sampler is used outdoors. For the purposes of this test method, refer to Practice D1357 for practices and planning ambient sampling events.
1.5 The organic compounds that have been successfully measured single-digit micrograms per cubic metre (µg/m3 (or single digit parts-per-billion by volume (ppbv)) concentration with this test method are listed in order of approximate retention time in Table 1. The test method is applicable to VOC concentrations ranging from the detection limit to approximately 1000 µg/m3 (300 ppbv). Above this concentration, smaller sample aliquots of sample gas may be analyzed or samples can be diluted with dry ultra-high-purity nitrogen or air or equivalent.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Safety practices should be part of the user’s SOP manual.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
