Metabolomics By Ion Mobility Mass Spectrometry

1
Metabolomics By Ion Mobility Mass
Spectrometry Prabha Dwivedi1 Kimberly A.
Kaplan1 Thomas F. Egan2 Agnes Tempez2 Albert
J. Schultz2 and Herbert H. Hill Jr1 1
Department of Chemistry Center for Multiphase
Environmental Research, Washington State
University, Pullman, WA 99164 2 Ionwerks Inc.,
Houston, TX
RESULT SUMMARY
RESULT SUMMARY
RESULTS
CONCLUSIONS
OVERVIEW

• Detection of 850 metabolites along with
  simultaneous separation of 250 isomeric
  metabolites was achieved by ESI-APIM-tof-MS.
• Under identical experimental conditions
  measurement of metabolites in nM concentration
  range demonstrated a maximal standard deviation
  of 0.1 amu in mass to charge ratio, 0.05 ms in
  drift time and 0.02 cm2 V-1s-1 in reduced
  mobility value.
• Extraction solvent and conditions effect the type
  and number of metabolites extracted.
• Four fold increase in the peak capacity of the
  mass spectrometer alone was observed by
  interfacing it to IMS as a pre-separation
  technique in second dimension.
• Results show that combined 2D information
  obtained by IMMS experiments can be applied as a
  powerful tool for separation and identification
  of metabolic features in complex matrices without
  performing extensive sample preparation.

Purpose Detection of metabolites in human blood
Method Ion Mobility Mass Spectrometry Results
Simultaneous detection of 850 metabolites and
separation of 250 isomers in human blood
metabolome achieved
2D contour plots 1. of human blood metabolome
(Left Top), 2. of an enlarged view in the m/z
range of 190-225 amu showing the separation of
isomers by IMS (Left Bottom), 3) of a close up
view in the m/z range of 600-750 amu showing the
application of ion mobility patterns to aid
interpretation of peaks observed in an IMMS
experiment (Right Top), and 4. demonstrating the
IMMS peak shapes with 3 and 5 ion counts (Right
bottom).
INTRODUCTION
Schematic of the ESI-APIMS-tofMS used for the
analysis of human blood metabolome. Primary units
in the instrument are Ion source (ESI), heated
atmospheric pressure desolvation region,
Bradbury-Nielsen ion gate, Counter-flow
atmospheric pressure drift region, differentially
pumped interface, ion extraction region,
orthogonal time-of-flight mass analyzer, and
Bipolar MCP detector.
Due to lack of efficient instrumental analytical
techniques that can rapidly analyze complex
biological samples and can provide sufficient
visualization of the metabolome, currently an
array of analytical methods is required for
comprehensive analysis of a metabolome. In
general, however, current analytical methods such
as LC, GC, and CE, with or without MS require
tedious sample preparation procedures prior to
analysis and are normally suited for
investigation only for a specific class of
metabolites. Ion mobility spectrometry, with its
resolving power comparable to that of GC its
sensitivity for the detection of analytes in nM
concentrations its high reproducibility in
measurement, its compatibility for interfacing
with GC, LC and MS its application to compounds
with diverse physical and chemical properties
without extensive sample preparations its
separation selectivity for isomeric molecules,
its durability and above all its short analysis
time is a perfect analytical method for
metabolomics. When used in tandem with MS, the
ability to differentiate low intensity analyte
peak from MS random noise by differentiation in
mobility space allows detection of low abundance
metabolites by IMS-MS.
Density profile of metabolites detected in human
blood metabolome by ESI-APIM-Tof-MS and with ion
signals 5 ion counts. On the x-axis is shown
the mass to charge ratio in amu and the y-axis
represents the measured density in amu/Å3.
Bar plot illustrating the distribution of number
of metabolic features detected in cold and hot
extraction methods with 5 averages and ion counts
5 ions.
EXPERIMENTAL
IMS used in this study was designed and
constructed at WSU and interfaced to an
orthogonal time of flight MS designed and
constructed at Ionwerks Inc., Houston via a
250-µm pinhole interface. The IMS drift tube was
operated at a temperature of 179oC and an
electric field of 558 V/cm. Blood metabolites
were extracted in methanol, ionized by ESI, size
separated by IMS, mass separated by o-Tof-MS and
detected by a bipolar MCP detector.
Peak capacity Illustration of the 2D space
(shaded area in the X-Y quadrant) occupied by
metabolites detected in human blood extract by
ESI- APIM-Tof-MS with 5 ion counts.
ACKNOWLEDGEMENTS
2D contour plots of the human blood metabolome in
sections of 100 amu
This work was supported in part by a grant from
National Institute of Health- Road Map Grant
R21-DK070274