4 research outputs found
Enhancing Computational Tools for LC-IM-MS-Based Small Molecule Workflows (ASMS 2017)
Ion
mobility spectrometry (IMS) is a rapid and highly reproducible molecular-shape
separation technique. While IMS has shown great utility when coupled with MS
for analysis of complex samples, methods for processing the complex data
generated have lagged behind. In fact, the incorporation of this extra IMS separation
dimension requires upgrades and optimization of existing computational
pipelines and the development of new algorithmic strategies to fully exploit
the advantages of the technology. Here, we investigate MS pre-processing algorithms
to extend feature detection and quantification performance, as well as
integration of IMS collisional cross section (CCS) libraries into data analysis
tools for molecular characterization. These strategies were applied for
untargeted analyzes of biofluid samples to evaluate changes in endogenous
metabolites and xenobiotics
An Interlaboratory Evaluation of Drift Tube Ion Mobility–Mass Spectrometry Collision Cross Section Measurements
Collision
cross section (CCS) measurements resulting from ion mobility–mass
spectrometry (IM-MS) experiments provide a promising orthogonal dimension
of structural information in MS-based analytical separations. As with
any molecular identifier, interlaboratory standardization must precede
broad range integration into analytical workflows. In this study,
we present a reference drift tube ion mobility mass spectrometer (DTIM-MS)
where improvements on the measurement accuracy of experimental parameters
influencing IM separations provide standardized drift tube, nitrogen
CCS values (<sup>DT</sup>CCS<sub>N2</sub>) for over 120 unique ion
species with the lowest measurement uncertainty to date. The reproducibility
of these <sup>DT</sup>CCS<sub>N2</sub> values are evaluated across
three additional laboratories on a commercially available DTIM-MS
instrument. The traditional stepped field CCS method performs with
a relative standard deviation (RSD) of 0.29% for all ion species across
the three additional laboratories. The calibrated single field CCS
method, which is compatible with a wide range of chromatographic inlet
systems, performs with an average, absolute bias of 0.54% to the standardized
stepped field <sup>DT</sup>CCS<sub>N2</sub> values on the reference
system. The low RSD and biases observed in this interlaboratory study
illustrate the potential of DTIM-MS for providing a molecular identifier
for a broad range of discovery based analyses
An Interlaboratory Evaluation of Drift Tube Ion Mobility–Mass Spectrometry Collision Cross Section Measurements
Collision
cross section (CCS) measurements resulting from ion mobility–mass
spectrometry (IM-MS) experiments provide a promising orthogonal dimension
of structural information in MS-based analytical separations. As with
any molecular identifier, interlaboratory standardization must precede
broad range integration into analytical workflows. In this study,
we present a reference drift tube ion mobility mass spectrometer (DTIM-MS)
where improvements on the measurement accuracy of experimental parameters
influencing IM separations provide standardized drift tube, nitrogen
CCS values (<sup>DT</sup>CCS<sub>N2</sub>) for over 120 unique ion
species with the lowest measurement uncertainty to date. The reproducibility
of these <sup>DT</sup>CCS<sub>N2</sub> values are evaluated across
three additional laboratories on a commercially available DTIM-MS
instrument. The traditional stepped field CCS method performs with
a relative standard deviation (RSD) of 0.29% for all ion species across
the three additional laboratories. The calibrated single field CCS
method, which is compatible with a wide range of chromatographic inlet
systems, performs with an average, absolute bias of 0.54% to the standardized
stepped field <sup>DT</sup>CCS<sub>N2</sub> values on the reference
system. The low RSD and biases observed in this interlaboratory study
illustrate the potential of DTIM-MS for providing a molecular identifier
for a broad range of discovery based analyses
Expanding Per- and Polyfluoroalkyl Substances Coverage in Nontargeted Analysis Using Data-Independent Analysis and IonDecon
Per- and polyfluoroalkyl substances (PFAS) are widespread,
persistent
environmental contaminants that have been linked to various health
issues. Comprehensive PFAS analysis often relies on ultra-high-performance
liquid chromatography coupled with high-resolution mass spectrometry
(UHPLC HRMS) and molecular fragmentation (MS/MS). However, the selection
and fragmentation of ions for MS/MS analysis using data-dependent
analysis results in only the topmost abundant ions being selected.
To overcome these limitations, All Ions fragmentation (AIF) can be
used alongside data-dependent analysis. In AIF, ions across the entire m/z range are simultaneously fragmented;
hence, precursor–fragment relationships are lost, leading to
a high false positive rate. We introduce IonDecon, which filters All
Ions data to only those fragments correlating with precursor ions.
This software can be used to deconvolute any All Ions files and generates
an open source DDA formatted file, which can be used in any downstream
nontargeted analysis workflow. In a neat solution, annotation of PFAS
standards using IonDecon and All Ions had the exact same false positive
rate as when using DDA; this suggests accurate annotation using All
Ions and IonDecon. Furthermore, deconvoluted All Ions spectra retained
the most abundant peaks also observed in DDA, while filtering out
much of the artifact peaks. In complex samples, incorporating AIF
and IonDecon into workflows can enhance the MS/MS coverage of PFAS
(more than tripling the number of annotations in domestic sewage).
Deconvolution in complex samples of All Ions data using IonDecon did
retain some false fragments (fragments not observed when using ion
selection, which were not isotopes or multimers), and therefore DDA
and intelligent acquisition methods should still be acquired when
possible alongside All Ions to decrease the false positive rate. Increased
coverage of PFAS can inform on the development of regulations to address
the entire PFAS problem, including both legacy and newly discovered
PFAS