Interferences of nitrogen dioxide in the determination of aldehydes and ketones by sampling on 2,4-dinitrophenylhydrazine-coated solid sorbent

Summary The influence of nitrogen oxides on the practicability and accuracy of the determination of aldehydes and ketones in air samples using the DNPH-method was examined. Nitrogen dioxide reacts with 2,4-dinitrophenylhydrazine and the reaction products were identified as 2,4-dinitrophenylazide (main product) and 2,4-dinitrochlorobenzene (by-product). They have a similar chromatographic behaviour in high performance liquid chromatography (HPLC) as formaldehyde-2,4-DNP-hydrazone. The chromatographic separation of the reaction products and formaldehyde-2,4-dinitrophenylhydrazone was performed using different gradient systems. Problems which occur in nitrogen dioxide-containing air samples are discussed.