FAIMS waveform optimization

HOD IMS methods (5.2.1). The magnitude of necessary for HOD IMS analyses of order n depends on the a values for ions of interest (rigorously, on the spreads between for the species to be resolved, 3.1.7). The most extensive compilations of 02 values are the measurements for 17 amino acid cations and anions that we looked at in the context of FAIMS waveform optimization (3.1). In that set, the means (medians) are 6.8x10 (6.0x10 ) Td for a-[ and 1.5x10 ° for fl2 the similarity of means and medians for either suggests that the selection of a and 02 values is representative. ... 

Characteristics of FAIMS Waveforms of Three Common Classes Optimized with Ed Constraint for a E/N) Expansions Limited to the First Two Terms... 

The quantity (F2) has been encountered in the formulas for average ion diffusion in FAIMS (3.1.2), which reflects the proportionality of diffusion coefhcient to ion temperature. Based on (F2) values for rectangular and bisinusoidal F t) with/=2 and clipped F t) with /= 2.51 that are optimum for K E/N) expansions tmncated to the first term (3.1.2 and 3.1.3), the maximum instantaneous Th at waveform peaks (Fn.max) exceeds Th by 2 times for the rectangular and 3.6 times for the harmonic-based F t). Profiles optimized for real K E/N) expansions including > 1 terms (3.1.4) may lead to somewhat lower or higher T H,max/ H values, depending on/by Equations 3.25 and 3.28. 

This chapter has described the use of asymmetric waveforms to separate and identify ion species based on the dependence of mobility on electric field intensity. We have reviewed the mechanism of differential mobility effect, the ways to quantify and maximize its magnitude, and the associated processes and limitations for various ion types. Understanding those issues allows us to start exploring and optimizing the performance of FAIMS systems depending on the instmmental parameters and ion properties. 

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