C
1-C
5 Aliphatic aldehydes in air were collected by passing a 10-100-l volume of air at 1l/min through a Sep-PAK C 18 impregnated with 2, 4-dinitrophenylhydrazine (DNPH) and phosphoric acid. The resulting derivatives were eluted with 2 ml of acetonitrile. The eluate, to which eicos ane and heneicosane were added as internal standards, was treated with a cation ion-exchange resin to remove the residual DNPH and other ionic contaminants. A 3-μl volume of the eluate thus obtained was analyzed by using a gas chromatograph equipped with a retention gap, Ultra-1 and D B-5 capillary columns connected in series and a flame ionization detector. The C
1-C
5 aldehydes and ketones were well resolved and sensitively determined at ppm-ppb levels with 0.6-2.2% rel ative standard deviations except for acrolein. The detection limits were 0.2-0.6 ppb for 100l of an air sample. For industrial emissions, aldehyde values determined by the proposed method were correlated to those by the conventional liquid chromatography.
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