Scope
1.1 This test method covers a procedure for the determination of formaldehyde (HCHO) and other aldehydes in air. This test method is specific for formaldehyde but, with modification, fourteen other aldehydes can be detected.
1.2 This test method involves drawing air through a cartridge containing silica gel coated with 2,4-dinitrophenylhydrazine (DNPH) reagent. Aldehydes and ketones readily form a stable derivative with the DNPH reagent. The DNPH derivative is analyzed for aldehydes and ketones utilizing high performance liquid chromatography (HPLC). The sampling procedure is a modification of U.S. EPA Method TO-11 (see 2.2).
1.3 This test method is based on the specific reaction of carbonyl compounds (aldehydes and ketones) with DNPH in the presence of an acid to form stable derivatives according to the reaction shown in Fig. 1, (where: both and are alkyl or aromatic groups (ketones), or both, or either or is a hydrogen atom (aldehydes)). The determination of formaldehyde, as a DNPH derivative, is similar to that of U.S. EPA Method TO-11 in that it utilizes HPLC. The detection limits have been extended to other aldehydes and ketones that can be determined as outlined in Section 13. This test method is suitable for determination of formaldehyde in the concentration range of high ppb to low ppm (v/v).
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 indoor air for formaldehyde.
1.5 The sampling flow rate, as described in this test method is presently limited to about 1.5 L/min. This limitation is principally due to the high pressure drop (>8 kPa at 1.0 L/min) across the DNPH-coated silica gel cartridges. This procedure is not compatible with pumps used in personal sampling equipment, that are inadequate for this application.
1.6 This test method instructs the user to purchase Sep-PAK chromatographic grade silica gel cartridges and apply acidified DNPH in situ to each cartridge, if the user desires to prepare his own cartridges. The silica gel in the Sep-PAK cartridge have a particle size of 55 to 105 [mu]m. Pre-coated DNPH silica gel cartridges are also available, if the user desires to purchase them.
1.7 The values stated in SI units are to be regarded as the standard.
1.8 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.
