Comparability of Steroid Collision Cross Sections Using Three Different IM-HRMS Technologies: An Interplatform Study

Steroids play key roles in various biological processes
and are
characterized by many isomeric variants, which makes their unambiguous
identification challenging. Ion mobility-mass spectrometry (IM-MS)
has been proposed as a suitable platform for this application, particularly
using collision cross section (CCS) databases obtained
from different commercial IM-MS instruments. CCS is
seen as an ideal additional identification parameter for steroids
as long-term repeatability and interlaboratory reproducibility of
this measurand are excellent and matrix effects are negligible. While
excellent results were demonstrated for individual IM-MS technologies,
a systematic comparison of CCS derived from all major
commercial IM-MS technologies has not been performed. To address this
gap, a comprehensive interlaboratory comparison of 142 CCS values derived from drift tube (DTIM-MS), traveling wave (TWIM-MS),
and trapped ion mobility (TIM-MS) platforms using a set of 87 steroids
was undertaken. Besides delivering three instrument-specific CCS databases, systematic comparisons revealed excellent
interlaboratory performance for 95% of the ions with CCS biases within ±1% for TIM-MS and within ±2% for TWIM-MS
with respect to DTIM-MS values. However, a small fraction of ions
(<1.5%) showed larger biases of up to 7% indicating that differences
in the ion conformation sampled on different instrument types need
to be further investigated. Systematic differences between CCS derived from different IM-MS analyzers and implications
on the applicability for nontargeted analysis are critically discussed.
To the best of our knowledge, this is the most comprehensive interlaboratory
study comparing CCS from three different IM-MS technologies
for analysis of steroids and small molecules in general.