S.O.P. No. MLD 022 - Determination of Carbonyl Compounds in Ambient Air
This document describes the procedures followed by the Monitoring and Laboratory staff in the determination of formaldehyde, acetaldehyde, and methyl ethyl ketone (MEK) in the ambient air. The carbonyl compounds are collected on a solid adsorbent and analyzed by High Performance Liquid Chromatography (HPLC). The method is developed based on U.S. EPA Method TO11. In this revision of the SOP, an ozone scrubber is installed upstream from the sampling cartridge. In addition, a silica sampling cartridge is found to be more efficient in collecting formaldehyde from the ambient air than the C-18 cartridge used in the previous Revision, 3.0. Silica cartridges, also have a lower level of acetone contamination than C-18 cartridges.
SUMMARY OF METHOD
Ambient is drawn through chromatographic grade Sep-Pak silica cartridge. The cartridges are coated with acidified 2,4-dinitrophenylhydrazine (DNPH). Sampling rate is set at 0.7 liters per minute for a 24-hour period. During sampling, formaldehyde, acetaldehyde, and methyl ethyl ketone react with the DNPH to form derivatives which are called hydrazone derivatives.
The DNPH derivatives are eluted from the sampling cartridges using acetone-free
acetonitrile (ACN) and are quantified using reverse-phase HPLC with ultraviolet
absorption detection at 360 nm.