PNNL

Abstract

The maximum electric field intensity (E) in FAIMS analyses was doubled to E ~60 kV/cm. Such strong fields cause electrical breakdown in ~1 mm gaps (for nearly all gases) and thus were impossible in earlier devices with 0.5 - 2.5 mm gaps. However, thinner gaps permit higher E, and >60 kV/cm was established here in semiconductor microchips with 35-µm gaps. As FAIMS efficiency is exceptionally sensitive to E, such extreme values allow accelerating analyses at same resolution by orders of magnitude. Here we demonstrate FAIMS ion filtering in ~20 µs, or ~1% of the previously needed time. The resolving power, though short of that for “macroscopic” FAIMS units, suffices for many applications. Microscopic gaps also enable concurrent ion processing in multiple (here, 47) channels, which greatly relaxes the charge capacity constraints of planar FAIMS approach. These microchips were integrated into stand-alone FAIMS and FAIMS/MS instruments with ions supplied by ß-radiation or electrospray sources, and evaluated in separations of small molecules, amino acids, and peptides. Present FAIMS analyzer can employ various pure and mixed gases, though the results depend on gas composition less than those with FAIMS using lower E. The measured separation performance is broadly in agreement with the first-principles modeling of FAIMS operation