Simple determination of relative hydrogen atom affinities by supercritical fluid chromatography/atmospheric pressure chemical ionization mass spectrometry

Coupled supercritical fluid chromatography and atmospheric pressure chemical ionization mass spectrometry was applied to estimate hydrogen atom affinities. The intensities of the M⁺ and MH⁺ peaks in the mass spectra were measured at various drift voltages (collision energies). The ratios of the two peaks were plotted against the drift voltages to obtain threshold drift voltages. The threshold drift voltages of polycyclic aromatic hydrocarbons were plotted and found to be proportional to the values of reported hydrogen atom affinities. The value for acenaphthylene was estimated to be 292.9 kJ mol^?1 from this relationship.