Effect of Traveling Waveform Profiles on Collision Cross Section Measurements in Structures for Lossless Ion Manipulations

We evaluated the effect of four different waveform profiles (Square, Sine, Triangle, and asymmetric Sawtooth) on the accuracy of collision cross section (CCS) measurements using traveling wave ion mobility spectrometry (TWIMS) separations in structures for lossless ion manipulations (SLIM). The effects of the waveform profiles on the accuracy of the CCS measurements wereevaluated for four classes of compounds (lipids, peptides, steroids,and nucleosides) at different TW speeds (126-206 m/s) andamplitudes (15-89 V). For the lipids and peptides, the (IMS)-I-TW-based CCS (TWCCS) deviations from the corresponding drift-tube-based CCS (DTCCS) measurements were significantly lowerin experiments conducted using the Sawtooth waveform comparedto the square waveform. This observation can be rationalized bythe lower maximum electricfield experienced by ions with a Sawtooth waveform, as compared to the other waveforms, resulting in alower probability for significant ion heating. We also observed that given approximately comparable resolution for all fourwaveforms, the Sawtooth waveform resulted in lower (CCS)-C-TW error and a better agreement with (CCS)-C-DT values than the Squarewaveform. In addition, for the steroids and nucleosides, an opposite (CCS)-C-TW trend was observed, with higher errors with theSawtooth waveform and lower with the Square waveform, suggesting that these molecules tend to become slightly more compactunder ion heating conditions. Under optimum conditions, allTWCCS measurements on the SLIM platform were within 0.5% of those measured in the drift tube ion mobility spectrometry.