Significance and Use
5.1 This test method provides an analytical procedure for measuring formaldehyde and other carbonyl compounds in indoor, workplace, outdoor air or for emission testing.
1.1 This test method presents a procedure for the determination of formaldehyde (HCHO) and other carbonyl compounds (aldehydes and ketones) in air. Other carbonyl compounds that have been successfully quantified by this method include acetaldehyde, acetone, propanal (propionaldehyde), 2-butanone (methyl ethyl ketone), butyraldehyde, benzaldehyde, isovaleraldehyde, valeraldehyde, o-tolualdehyde, m-tolualdehyde, p-tolualdehyde, hexanal, and 2,5-dimethylbenzaldehyde.
1.2 This test method involves drawing air through a cartridge containing silica gel coated with 2,4-dinitrophenylhydrazine (DNPH) reagent. Carbonyl compounds readily form stable derivatives with the DNPH reagent. The DNPH derivatives are analyzed for parent aldehydes and ketones utilizing high performance liquid chromatography (HPLC). The sampling procedure is a modification of U.S. EPA Method TO-11A (see ).
1.3 This test method is based on the specific reaction of carbonyl compounds with DNPH in the presence of an acid to form stable derivatives according to the reaction shown in , (where: both R and R1 are alkyl or aromatic groups (ketones), or either, or both R or R1 is a hydrogen atom (aldehydes)). The determination of formaldehyde and other carbonyl compounds, as DNPH derivatives, is similar to that of U.S. EPA Method TO-11A in that it utilizes HPLC with UV detection as the analytical finish. The applicability of this test method is extended beyond the stated applicability of TO-11A to include other carbonyl compounds that can be determined as stated in . This test method is suitable for determination of formaldehyde and other carbonyl compounds in the concentration range from approximately 10 ppb to 1 ppm (v/v). Lower concentrations may be determined with careful control of contamination, appropriate selection of flow rate and sampling duration.
1.4 The sampling method gives a time-weighted average (TWA) sample. It can be used for long-term (1 to 24 h) or short-term (5 to 60 min) sampling of air for formaldehyde. Shorter sampling times or low flow rates will result in higher detection limits and may result in greater variation in co-located sampler results. Tests should be performed over a duration and a flow rate that allows the data quality objective of the project to be achieved. Sample times for other carbonyls, such as acetaldehyde, may be limited to short term (. ) The data provides total concentrations of carbonyl compounds from which time weighted average concentrations can be calculated.
1.5 This test method instructs the user on how to prepare sampling cartridges from commercially available chromatographic grade silica gel cartridges by the application of acidified DNPH to each cartridge.
1.6 The sampling flow rate, as described in this test method, has been validated for sampling rates up to 1.5 L/min for formaldehyde. This flow rate limitation is principally due to the high pressure drop (>8 kPa at 1.0 L/min) across the user prepared silica gel cartridges which have a particle size of 55 to 105 µm. These cartridges are not generally compatible with battery-powered pumps used in personal sampling equipment (for example, those used by industrial hygienists).
1.7 Alternatively, pre-coated DNPH silica gel cartridges are also commercially available and may be substituted provided they can be demonstrated to perform equivalently (. Some of these use silica gel of a larger particle size that results in a lower pressure drop across the cartridge. These low pressure drop cartridges may be more suitable for sampling air using battery-powered personal sampling pumps. )
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.9 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 and health practices and determine the applicability of regulatory limitations prior to use.