MEASUREMENT OF SUB-PPBV CONCENTRATIONS OF ALDEHYDES IN A FOREST ATMOSPHERE USING A NEW HPLC TECHNIQUE

Aldehydes present in "clean" forest air (Niwot Ridge, CO, 3050-m altitude) were trapped on glass microcartridges containing porous glass particles impregnated with dansylhydrazine (DNSH) and analyzed on-line by HPLC with fluorescence detection. The detection limits of formaldehyde and acetaldehyde are 0.1 ppbv for 1-L air samples obtained at a sampling rate of 100 mL/min for 10 min. However, both field and laboratory studies show that, as for the conventional 2,4-dinitrophenylhydrazine method, ozone is a significant interference when its concentration exceeds 150 ppbv. Preliminary work indicates that N,N',N',-tetramethyl-1,4-phenylenediamine dihydrochloride may be added to the reagent solution at the time of cartridge preparation to serve as an ozone scavenger and reduce the ozone interference. The high sensitivity of the DNSH/microcartridge technique allowed the detection of emissions of aldehydes by trees, including aspens, pines, and willows. Besides p-hydroxybenzaldehyde and 2-hexenal, other C6 aldehydes containing hydroxyl groups and C=C double bonds were tentatively identified in tree emissions.