Accelerated High-Resolution Differential Ion Mobility Separations Using Hydrogen

The resolving power of differential ion mobility spectrometry (FAIMS) was dramatically increased recently by carrier gases comprising up to 75% He or various vapors, enabling many new applications. However, the need for resolution of complex mixtures is virtually open-ended and many topical analyses demand yet finer separations. Also, the resolving power gains are often at the expense of speed, in particular making high-resolution FAIMS poorly compatible with online liquid-phase separations. Here, we report FAIMS employing hydrogen, specifically in mixtures with N-2 containing up to 90% H-2. Such compositions raise the mobilities of all ions and thus the resolving power beyond that previously feasible, while avoiding the electrical breakdown inevitable in He-rich mixtures, The increases in resolving power and ensuing peak resolution are especially significant at H-2 fractions above similar to 50%. Higher resolution can be exchanged for acceleration of the analyses by up to similar to 4 times. For more mobile species such as multiply charged peptides, this exchange is presently forced by the constraints of existing PALMS devices, but future designs optimized for H-2 should consistently improve resolution for all analytes.