A measured volume of aqueous sample, approximately 100 mL, is buffered to pH 3 and the analytes are derivatized at 40'C for 1 hr with 2,4-dinitrophenylhydrazine (DNPH). The derivatives are extracted from the water by passing the sample through a series of 3 cartridges each of which contains 500 mg of a chemically bonded C18 organic phase (liquid-solid extraction, LSE). The solid sorbent cartridges are then eluted with 10 mL of ethanol. LSE disks may also be used as long as all the (QC) criteria specified in this method are met. Liquid chromatographic conditions are described which permit the separation and measurement of the carbonyl compounds in the extract by absorbance detection at 360 nm.