Trapped Ion Mobility Improves Annotation Accuracy in LC-HRMS Screening Applications for Exposomics

Ion mobility techniques coupled to mass spectrometry,
such as trapped
ion mobility (TIMS), are promoted to separate analytes from coeluting
matrix interferences and to resolve isomers based on their corresponding
CCS values. Complementary to the retention time (RT) dimension revealed
from liquid chromatography, the collision cross section (CCS) serves
as a robust and matrix-independent parameter. We evaluated the advantages
of TIMS in the screening of human samples, such as urine, serum, breastmilk,
and matrices relevant for exposure analysis, such as dust and wastewater.
We conducted a screening library for 769 environmental contaminants,
which resulted in a total of 948 CCS values (594 positive and 354
negative ionization modes). We screened for the potential co-occurrence
of interfering compounds originating from five different matrix backgrounds,
leading to peaks with similar m/z and RT but differences in the mobilograms. For all matrices combined,
112 peaks with different mobility values relative to the reference
standard were found. Our evaluation highlights the benefits of TIMS
in reducing the number of inconclusive assignments through the separation
of coeluting compounds and background noise and gaining a high MS2 coverage for low-abundant ions. These advantages are beneficial
especially for suspect screening applications, where broader RT windows
are necessary.