Liquid chromatography analysis of carbonyl (2,4-dinitrophenyl)hydrazones with detection by diode array ultraviolet spectroscopy and by atmospheric pressure negative chemical ionization mass spectrometry

The (2,4-dinitrophenyl)hydrazones of carbonyls are separated by liquid chro matography and detected by ultraviolet spectroscopy (diode array detector) and by atmospheric pressure negative chemical ionization mass spectrometry, Results are presented for 78 carbonyls including 18 1-alkanals (from forma ldehyde to octadecanal), 16 other saturated aliphatic carbonyls (5 C-4-C-7 aldehydes and 11 C-3-C-9 ketones), 16 unsaturated aliphatic carbonyls (9 C- 3-C-11 aldehydes and 7 C-4-C-9 ketones), 13 aromatic carbonyls (including h ydroxy- and/or methoxy-substituted compounds), 10 C-2-C-10 aliphatic dicarb onyls, 3 aliphatic carbonyl esters, and 2 other carbonyls, Isomers were obs erved for alpha,beta-unsaturated ketones and saturated carbonyls that bear other oxygen-containing substituents, e,g. methoxyacetone, 2-furaldehyde, a nd the 3 carbonyl esters, For ail but two of the carbonyls studied, the bas e peak in the negative APCI mass spectrum was the M - 1 ion (NO2)(2)C6H3NN= CR1R2 (R-1 = H for aldehydes), where M is the molecular mass of the carbony l (2,4-dinitrophenyl)hydrazone derivative. The dicarbonyls 2,4-pentanedione and succinic dialdehyde reacted with DNPH to yield predominantly other pro ducts. Concentrations measured by ultraviolet spectroscopy (peak area) and by mass spectrometry (abundance of RI - 1 ion) were in good agreement. Appl ications described include the measurement of 34 C-1-C-18 carbonyls at leve ls of 0.015-14 parts per billion (ppb) in urban air and the identification of carbonyls at ppb concentrations as reaction products in laboratory studi es of the atmospheric oxidation of unsaturated organic compounds.