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Resolution Enhancement of Ion Mobility Spectrometry by Improving the Three-Zone Properties of the Bradbury-Nielsen Gate

Du, Yongzhai, Wang, Weiguo, Li, Haiyang
Analytical chemistry 2012 v.84 no.3 pp. 1725-1731
chlorides, electric field, models, spectroscopy
A simple space compression-dispersion model for ion transport at ambient pressure was mathematically established. On the basis of this model and aided by SIMION simulation, a three-zone theory was proposed to characterize the Bradbury-Nielsen gating electric field features as three zones: the depletion zone, the dispersion zone, and the compression zone. Then, the influences of gating voltage difference increases on the full width at half-maximum of the Cl– peak were investigated in detail to verify the theory. For example, at a gating voltage difference of 350 V and a gate pulse width of 0.34 ms, the ion packets injected were reduced to as low as 60% of their original widths, with the peak height increased from 756 to 808 pA and the resolution from 18 to 33, enhanced by 7% and ∼80%, respectively. The ion mobility spectrometry (IMS) efficiency ratios, Rₘ/Rc and Rₘ/Rₚ, were also raised above theoretical values and reached about 182% and 175%, respectively. The experimental results were explained using the proposed theory with good consistency. Finally, a compression coefficient was extracted by fitting the experimental data to the applied gate pulse width, presenting a good linearity. All this shows a potential application in improving the performances of ion mobility spectrometry.