Comparison between two carbonyl measurement methods in the atmosphere

Two atmospheric aldehyde sampling techniques, the impinger method in which aldehydes are trapped in a 2,4-dinitrophenylhydrazine acidified acetonitril e solution, and the method in which aldehydes are captured in 2,4-dinitroph enylhydrazine acidified coated cartridges commercialised by the WATERS(R), were compared for blank values, sample preservation, ozone action, and wate r influence. The two methods were tested in a Paris atmosphere and the infl uence of a KI ozone scrubber has been evaluated. Except for acetaldehyde an d benzaldehyde, the two techniques do not give coherent results. When no oz one scrubber is used, the cartridge technique gives systematically lower va lues. Bad correlation has been obtained between data with scrubber and data without scrubber for the impinger technique except for acetaldehyde. For t he cartridge technique, the correlation is better for all the aldehydes but higher values are found when a scrubber is used, except for formaldehyde. Ozone action leads to 2,4-dinitrophenylhydrazone destruction, but also to f ormaldehyde 2,4-dinitrophenylhydrazone formation by reaction between airbor ne volatile organic compounds and ozone on the cartridge surfaces.