A standard operating protocol (SOP) has been developed for the measurement of low concentrations (parts per billion) of aldehydes and ketones in air. The method involves sampling with small carbon-18 cartridges impregnated with a selective reagent, 2, 4-dinitrophenylhydrazine. The carbonyl-2, 4-dinitrophenylhydrazones thus formed are eluted from the cartridges with acetonitrile. They are separated and quantified by High Performance Liquid Chromatography (HPLC) using a photodiode array UV-Vis detector. Identification of components is based upon comparison of their retention times and ultraviolet-visible spectra with those of standards. Quantitation is obtained from peak area versus concentration calibration curves. -- AATA