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 chromatography 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 formaldehyde 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 hydroxy- and/or methoxy-substituted compounds), 10 C-2-C-10 aliphatic dicarbonyls, 3 aliphatic carbonyl esters, and 2 other carbonyls, Isomers were observed for alpha,beta-unsaturated ketones and saturated carbonyls that bear other oxygen-containing substituents, e,g. methoxyacetone, 2-furaldehyde, and the 3 carbonyl esters, For ail but two of the carbonyls studied, the base 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 carbonyl (2,4-dinitrophenyl)hydrazone derivative. The dicarbonyls 2,4-pentanedione and succinic dialdehyde reacted with DNPH to yield predominantly other products. Concentrations measured by ultraviolet spectroscopy (peak area) and by mass spectrometry (abundance of RI - 1 ion) were in good agreement. Applications described include the measurement of 34 C-1-C-18 carbonyls at levels of 0.015-14 parts per billion (ppb) in urban air and the identification of carbonyls at ppb concentrations as reaction products in laboratory studies of the atmospheric oxidation of unsaturated organic compounds.