Field induced displacement reactions with proton bound dimers of organophosphorus compounds in a tandem differential mobility spectrometer.

Endothermic displacement reactions between proton bound dimers of organophosphorus compounds (OPCs) and isopropanol (IPA) were enabled in air at ambient pressure with tandem differential mobility spectrometry (DMS). Proton bound dimers (M2H+) were mobility isolated in purified air with a first DMS stage, mixed with IPA at ≥100 ppm in a middle reactive stage at 106 to 160 Td from a symmetrical 4 MHz waveform, and mobility analyzed in a second DMS stage. Although the enthalpy for displacement of M by IPA in M2H+ is unfavorable by +44 to 50 kJ mol-1, formation of the heterogenous proton bound dimer, MH+(IPA) arises from field induced dissociation of M2H+ to MH+ and addition of IPA.