Characterization of chemical interferences in the determination of unsaturated aldehydes using aromatic hydrazine reagents and liquid chromatography

A systematic investigation on interferences in the determination of unsatur ated aldehydes and ketones using the 2,4-dinitrophenylhydrazine (DNPH) meth od is described. Acrolein, crotonaldehyde, methacrolein and 1-buten-3-one a re derivatized with DNPH in the presence of an acidic catalyst to form the respective hydrazones. The unstable hydrazones react with excess reagent to form adducts. These are identified by high-performance liquid chromatograp hy (HPLC)-mass spectrometry and spectroscopic techniques after cryogenic fr action collection of the adducts. The quantification of the unsaturated car bonyls with the DNPH method remains difficult. N-Methyl-4-hydrazino-7-nitro benzofurazan (MNBDH) was used as an alternative reagent for this purpose. A s with DNPH, the formation of a side product is observed. In contrast to DN PH, the alteration of the pH immediately after sampling leads to only one r eaction product, which is stable and storable in solution at 4 degreesC for 2 days.