ION MOBILITY COUPLED TO HIGH RESOLUTION MASS SPECTROMETRY: THE POSSIBILITIES, THE LIMITATIONS

Transcription

1 ION MOBILITY COUPLED TO HIGH RESOLUTION MASS SPECTROMETRY: THE POSSIBILITIES, THE LIMITATIONS Anton Kaufmann Official Food Control Authority of the Canton of Zurich (Kantonales Labor Zürich) Switzerland

2 Ions are more mobile than Ion mobility mass spectrometers Very first shipped VION instrument (17. December 2015)

3 Ion Mobility Ion Mobility FAIMS (Field Asymmetric Waveform IMS) DTIMS (Drift time IMS)

4 FAIMS (Field Asymmetric Waveform IMS) Volt O Volt Volt buffer gas Ion source MS Polarity gradient

5 DTIMS (Drift time IMS) buffer gas Trap MS Polarity gradient

6 Why drift time IMS? Drift time IMS produces comprehensive data (Sampling of all masses for all drift times) Drift time IMS produces collision cross section (CCS)

7 m/z versus IMS

8 6-10 data points across a chromatographic peak IMS IMS Relative Abundance IMS IMS IMS IMS IMS TOF

9 Cross collision section CCS Characteristic property of a compound

10 Cross collision section is not truly orthogonal to m/z CCS versus m/z ccs m/z RT versus m/z rt [min] m/z

11 Ion mobility cleans up MS spectra

12 Ion mobility cleans up MS spectra m/z Drift time

13 Componentization A spike is not a peak A peak is not yet a compound

14 Componentization (Extraction of multidimensional features) Column bleed m/z noise Retention time

15 Cumulative filtering of MS E data Alternating between unfragmented and fragmented traces (MS E : no precursor selection) Resulting product ion spectra would be very «dirty» Componentization and drift time filtering produces «clean» product ion spectra

16 Nitrofuran metabolite AOZ 10 µg/kg In In Liver Standard extract Low energy (no fragmentation) high energy (fragmentation)

17 The strategy towards the use of virtual reference substances All ion fragmentation (MS E ) produces a comprehensive set of all precursor and product ions Componentization and IMS filtering produce clean product ion spectra The observed fragments can be compared with those suggested by the in-silico fragmentation of a targeted, virtual reference compound (in silico fragmentation)

18 Virtual reference compound based screening Needed: - Molfile from ChemSpider Not needed: - Physical reference compound - Retention time - Mass - Product ion spectrum - Ion mobility data

19 in-silico fragmentation based on Molfiles

20 in silico fragmentation based on Molfiles 5 penalties 1 penalty 2 penalties Brute force and a little bit of chemical intelligence

21 Mass spectrum explained by in-silico fragmentation

22 A realistic concept or wishful thinking? Participation in RIKILT proficiency study (Antibiotics in bovine muscle 2016) Extracts were screened by relying on the concept of virtual reference substances Utilized were Molfiles of 114 Vet. Drugs (downloaded from ChemSpider.com) (considered were: H + ; Na + H 2 ++ )

23 Was the approach successful? Last week RIKILT released the screening results: RIKILT asked to hide these result in the printed version This corresponds to our submitted results

24 IMS-HRMS Advantages of IMS-HRMS Care-free hyphenation (unlike two-dimensional LC) CCS values are reported to be robust, and can «almost» be calculated Extremely clean non-precursor selected product ion spectra even for non-targeted analytes

25 IMS-HRMS Disadvantage of IMS-HRMS 4 D feature extraction can be very slow CCS are not really orthogonal to m/z IMS-HRMS instrumentation is still a new technology IMS can reduce ion transmission and induce pre collisioncell fragmentation

26 Future of IMS-HRMS More and more vendors are selling IMS systems Improvements with hyphenation (e.g. dynamic range; sensitivity) are to be expected IMS resolving power will increase Better and faster data-processing software can be expected

27 Thank you for your attention