The automation oja method Jor the simultaneous determinationoj nitrogen oxides, aldehydes and ketones is explained, and itsapplicability is shown by means ojseveralfield tests. Allcomponentswere sampled together using impingers filled with a solution oj2,4-dinitrophenylhydrazine(DNPH). The corresponding derivatives were separated by HPLC and quantified by UV/ Visabsorbance at