Enthalpy of Solution and Kovats Retention Indices for Nitroaromatic Compounds on Stationary Phases Using Gas Chromatography

Worldwide terrorism has recently resulted in increased efforts to detect and identify explosive residues. Availability of experimentally determined thermochemical data for explosive compounds and their degradation products is limited, however. Gas chromatography was used to determine the enthalpy of solution, Delta H-sol, for a series of nitroaromatic explosives and explosive degradation products including nitrobenzene, 2-nitrotoluene, 3-nitrotoluene, 4-nitrotoluene, 1,2-dinitrobenzene, 1,3-dinitrobenzene, 1,4-dinitrobenzene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, 3,4-dinitrotoluene, 3,5-dinitrotoluene, 1,3,5-trinitrobenzene, and 2,4,6-trinitrotoluene. Four polar stationary phases (by mass composition), namely, 80 % dimethyl + 20 % diphenyl polysiloxane, 14 % cyanopropylphenyl + 86 % dimethyl polysiloxane, 50 % phenyl + 50 % methyl polysiloxane, and 100 % polyethylene glycol, were evaluated with the 13 nitroaromatic compounds. Isothermal Kovats retention indices are also reported for the nitroaromatics as well as the Delta H-sol of several n-alkanes. Enthalpies reported herein were computed over a wide temperature range, thus net retention volumes are also tabulated to facilitate the specific needs of interested readers.