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Paper "Determination of the Molar Fraction and Enantiomeric Excess of Electrosprayed Amino Acid Anions Employing Photoelectron Circular Dichroism" published in "Analytical Chemistry"

Jon Henrik Both, Anastasiya Beliakouskaya, Karl-Michael Weitzel
Fachbereich Chemie, Philipps-Universität Marburg, 35032 Marburg, Germany

The quantification of molar fractions and enantiomeric excess have been demonstrated in mixtures of d- and l-tryptophan and d- and l-phenylalanine, respectively, avoiding derivatization of the analyte with additional reagents or separation steps. The technique is based on an electrospray ionization (ESI) which allows to generate anions of non-volatile compounds such as amino acids or large biomolecules. Electrons are photo-detached from these anions. The distribution of forward and backward scattered photoelectrons is analyzed, leading to the photoelectron circular dichroism (PECD), the observable of interest. The quantification of the concept is proven by blind measurements analyzing mixtures of unknown composition. The quantification of enantiomeric excess (ee) values is not only possible for signal originating from the molecular anion but also for the molecular dimer anion. The ESI-PECD technique is known to be applicable to large chemical entities of several thousand Daltons.

Analytical Chemistry, accepted (2025)
view article online at: https://doi.org/10.1021/acs.analchem.4c05964