Improving Target and Suspect Screening High-Resolution Mass Spectrometry Workflows in Environmental Analysis by Ion Mobility Separation

Currently,
the most powerful approach to monitor organic micropollutants
(OMPs) in environmental samples is the combination of target, suspect,
and nontarget screening strategies using high-resolution mass spectrometry
(HRMS). However, the high complexity of sample matrices and the huge
number of OMPs potentially present in samples at low concentrations
pose an analytical challenge. Ion mobility separation (IMS) combined
with HRMS instruments (IMS–HRMS) introduces an additional analytical
dimension, providing extra information, which facilitates the identification
of OMPs. The collision cross-section (CCS) value provided by IMS is
unaffected by the matrix or chromatographic separation. Consequently,
the creation of CCS databases and the inclusion of ion mobility within
identification criteria are of high interest for an enhanced and robust
screening strategy. In this work, a CCS library for IMS–HRMS,
which is online and freely available, was developed for 556 OMPs in
both positive and negative ionization modes using electrospray ionization.
The inclusion of ion mobility data in widely adopted confidence levels
for identification in environmental reporting is discussed. Illustrative
examples of OMPs found in environmental samples are presented to highlight
the potential of IMS–HRMS and to demonstrate the additional
value of CCS data in various screening strategies.