Direct Mass Spectrometry of Chiral Molecules: MS-PECD

Here you will find information about a novel technology for the enantiomer-selective detection of chiral molecules called Mass Selective - Photo Electron Circular Dichroism (MS-PECD). MS-PECD is a laser-based table-top technology that provides direct Mass Spectrometry of chiral molecules and enantiomeric excess measurement in complex chiral mixtures.

The forward-backward asymmetry of the electron angular distribution along the laser beam (Photo Electron Circular Dichroism, PECD) is measured on the electron imaging detector. The molecular ion is also detected in coincidence with the electron on a time-sensitive particle detector, providing the mass of the chiral molecule from the ion Time-of-Flight. Every electron is tagged by the mass of the ion that it originated from. The (electron,ion) correlation and the measured PECD provide a direct Mass Spectrometric indentification of the enantiomers present in the chiral mixture. The magnitude of the MS-PECD asymmetry of every molecule in the multi-component mixture scales directly to the enantiomeric excess of the compound.Advantages, capabilities and potential of MS-PECD

1. PECD has large enantiomeric sensitivity, typically between 1-10%, a factor of 100-1000 larger than CD, VCD or ROA.

2. Mass-Selected PECD gives direct enantiomeric selectivity of every chiral molecule observed in the mass spectrum.

3. Direct quantitative measurement of the enantiomeric excess of chiral molecules in multi-component mixtures.

4. No prior enantiomeric separation of the sample with chiral GC, HPLC, SFC or IMS is needed before MS-detection.

5. No prior enantiomeric selective clustering of the sample with chiral ligands is needed before MS-detection.

6. Laser ionization via intermediate vibronically excited states provides additional spectral selectivity and identification.

7. The electron kinetic energy spectrum provides additional spectroscopic information on the correlated ion.

8. MS-PECD is performed with a table-top laser-based spectrometer.

9. Ionization with an ultrafast intense laser is a universal ionization technique for molecules providing soft-ionization.

10. MS-PECD in combination with spatially selective (laser) desorption techniques provides spatial chiral sensitivity.

Detailed information on the science, the technology and analytical applications is provided in the following publications:

Enantiomer-specific analysis of multi-component mixtures by correlated electron imaging–ion mass spectrometry

Mohammad M Rafiee Fanood, N. Bhargava Ram, C. Stefan Lehmann, Ivan Powis and Maurice H.M. Janssen

Nature Communications 6, 7511 (2015) pdf link

Imaging photoelectron circular dichroism of chiral molecules by femtosecond multiphoton coincidence detection

C. Stefan Lehmann, N. Bhargava Ram, Ivan Powis, and Maurice H. M. Janssen

The Journal of Chemical Physics 139, 234307 (2013) pdf link

Awarded the 2013 JCP Editors` choice for groundbreaking research in Chemical Physics.

Detecting chirality in molecules by imaging photoelectron circular dichroism

Maurice H.M. Janssen and Ivan Powis

Phys. Chem. Chem. Phys. 16, 856 (2014) pdf link

Invited Perspective.

For a historic review of the development of laser-based MS-PECD see the special technology page at this link.

Recent citations to review papers on laser-based and synchrotron-based PECD:

Review on Laser-based PECD by Janssen and Powis, PhysChemChemPhys: Google Scholar citations

Review on Synchrotron-based PECD by Nahon, Garcia and Powis, J. of Elec. Spec. & Rel. Phen.: Google Scholar citations