Identification of chemical interferences in aldehyde and ketone determination using dual-wavelength detection.

A method for the rapid and convenient identification of chemical interferences in the determination of aldehydes and ketones in air samples using the 2,4-dinitrophenylhydrazine (DNPH) method is described. The ratio of absorptions at 360 and 300 nm is characteristic for groups of related aldehydes and ketones as well as for the main interferents. It has been determined by UV/visible spectroscopy of pure standard compounds and confirmed by HPLC analysis with UV/visible detection of complex hydrazone mixtures. The application of this method has led to the identification of 2,4-dinitrochlorobenzene as another interfering compound after sampling of air with high nitrogen dioxide content when using hydrochloric acid as catalyst. The possibilities and limitations of the dual-wavelength detection with the DNPH method are discussed for mixtures of standards and real samples from car exhaust.