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

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Abstract
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 C4−C7 aldehydes and 11 C3−C9 ketones), 16 unsaturated aliphatic carbonyls (9 C3−C11 aldehydes and 7 C4−C9 ketones), 13 aromatic carbonyls (including hydroxy- and/or methoxy-substituted compounds), 10 C2−C10 aliphatic dicarbonyls, 3 aliphatic carbonyl esters, and 2 other carbonyls. Isomers were observed for α,β-unsaturated ketones and saturated carbonyls that bear other oxygen-containing substituents, e.g. methoxyacetone, 2-furaldehyde, and the 3 carbonyl esters. For all but two of the carbonyls studied, the base peak in the negative APCI mass spectrum was the M − 1 ion (NO2)2C6H3NNCR1R2 (R1 = 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 M − 1 ion) were in good agreement. Applications described include the measurement of 34 C1−C18 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.

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