Krylova N, Krylov E, Eiceman G A, Stone J A
Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, New Mexico 88003, USA.
J Phys Chem A. 2003 May 15;107(19):3648-54. doi: 10.1021/jp0221136.
The electric field dependence of the mobilities of gas-phase protonated monomers [(MH+(H2O)n] and proton-bound dimers [M2H+(H2O)n] of organophosphorus compounds was determined at E/N values between 0 and 140 Td at ambient pressure in air with moisture between 0.1 and 15 000 ppm. Field dependence was described as alpha (E/N) and was obtained from the measurements of compensation voltage versus field amplitude in a planar high-field asymmetric waveform ion mobility spectrometer. The alpha function for protonated monomers to 140 Td was constant from 0.1 to 10 ppm moisture in air with onset of effect at approximately 50 ppm. The value of alpha increased 2-fold from 100 to 1000 ppm at all E/N values. At moisture values between 1000 and 10 000 ppm, a 2-fold or more increase in alpha (E/N) was observed. In a model proposed here, field dependence for mobility through changes in collision cross sections is governed by the degree of solvation of the protonated molecule by neutral molecules. The process of ion declustering at high E/N values was consistent with the kinetics of ion-neutral collisional periods, and the duty cycle of the waveform applied to the drift tube. Water was the principal neutral above 50 ppm moisture in air, and nitrogen was proposed as the principal neutral below 50 ppm.
在环境压力下，于空气中湿度介于0.1至15000 ppm之间、E/N值介于0至140 Td的条件下，测定了有机磷化合物的气相质子化单体[(MH+(H2O)n]和质子键合二聚体[M2H+(H2O)n]迁移率的电场依赖性。电场依赖性用α(E/N)来描述，它是通过在平面高场不对称波形离子迁移谱仪中测量补偿电压与场强幅度而获得的。对于质子化单体，在空气中湿度从0.1至10 ppm且α函数至140 Td时保持恒定，在约50 ppm时开始出现效应。在所有E/N值下，α值从100 ppm增加到1000 ppm时增大了2倍。在湿度值介于1000至10000 ppm之间时，观察到α(E/N)增大了2倍或更多。在此提出的一个模型中，通过碰撞截面变化实现的迁移率电场依赖性由质子化分子被中性分子的溶剂化程度决定。在高E/N值下离子去簇过程与离子 - 中性碰撞周期的动力学以及施加到漂移管的波形占空比一致。在空气中湿度高于50 ppm时，水是主要的中性分子，而在低于50 ppm时，提出氮气是主要的中性分子。
