QUANTIFICATION OF 2,4-DINITROPHENYL-HYDRAZONES OF LOW-MOLECULAR-MASS ALDEHYDES AND KETONES USING HPLC

This study was undertaken to evaluate the HPLC separation and quantification of several low molecular mass aldehydes and ketones, which may be produced during combustion in alcohol-fueled automobiles, by means of their dinitrophenylhydrazone derivatives. Stationary phases (ODS), mobile phase components (acetonitrile or methanol with water) and detection sensitivity at 254 and 365 nm were evaluated. Separation of eight dinitrophenylhydrazones could be achieved in approximately 20 minutes using a Zorbax ODS or a Supelcosil LC-PAH column with a MeOH:H2O (75:25 v/v) mobile phase. Complete separations were not obtained with either a Nova-Pack C-18 or an Ultrasphere ODS column. The use of acetonitrile-water mobile phases produces poorer resolution at all compositions tested. Quantification of the compounds by several methods was compared, with the lowest standard deviations being seen with the external standard method. The detection limit at 365 nm is less than 1.5 pmol for each of the 2,4-dinitrophenyl-hydrazones in the test solution. The method is being applied to the analysis of aldehydes and ketones in the exhaust of automobile engines fueled by ethanol-gasoline mixtures.