Sample preparation including sonication and solid phase extraction has been developed for the determination of carbonyl compounds in atmospheric aerosol. Aerosol samples were sonicated in acidified acetonitrile containing 2,4-dinitrophenylhydrazine (DNPH) to form hydrazone derivatives of aldehydes and ketones. Water was added to the extract to increase its polarity. Then the solution was passed through an octadecyl or phenyl solid phase extraction cartridge. The concentrated hydrazone derivatives were eluted with tetrahydrofuran, the eluate was evaporated to dryness then dissolved in acetonitrile/water mixture and finally analysed by RP-HPLC with UV detection at 360 nm. The absolute detection limits of the individual carbonyl compounds range from 0.4 to 5.8 ng.