Capillary electrophoresis-mass spectrometry of derivatized amino acids for targeted neurometabolomics - pH mediated reversal of diastereomer migration order

Radu-Cristian Moldovan; Ede Bodoki; Anne-Catherine Servais; Bezhan Chankvetadze; Jacques Crommen; Radu Oprean; Marianne Fillet

doi:10.1016/j.chroma.2018.06.030

Capillary electrophoresis-mass spectrometry of derivatized amino acids for targeted neurometabolomics - pH mediated reversal of diastereomer migration order

J Chromatogr A. 2018 Aug 24:1564:199-206. doi: 10.1016/j.chroma.2018.06.030. Epub 2018 Jun 13.

Authors

Radu-Cristian Moldovan¹, Ede Bodoki², Anne-Catherine Servais³, Bezhan Chankvetadze⁴, Jacques Crommen³, Radu Oprean², Marianne Fillet⁵

Affiliations

¹ Laboratory for the Analysis of Medicines, Department of Pharmacy, Faculty of Medicine, CIRM, University of Liege, Avenue Hippocrate 15, B36, +3, Tower 4, 4000, Liege, Belgium; Department of Analytical Chemistry and Instrumental Analysis, Faculty of Pharmacy, "Iuliu Haţieganu" University of Medicine and Pharmacy Cluj-Napoca, 4 Louis Pasteur street, 400349, Cluj-Napoca, Romania.
² Department of Analytical Chemistry and Instrumental Analysis, Faculty of Pharmacy, "Iuliu Haţieganu" University of Medicine and Pharmacy Cluj-Napoca, 4 Louis Pasteur street, 400349, Cluj-Napoca, Romania.
³ Laboratory for the Analysis of Medicines, Department of Pharmacy, Faculty of Medicine, CIRM, University of Liege, Avenue Hippocrate 15, B36, +3, Tower 4, 4000, Liege, Belgium.
⁴ Institute of Physical and Analytical Chemistry, School of Exact and Natural Sciences, Tbilisi State University, Chavchavadze Ave 3, Tbilisi, Georgia.
⁵ Laboratory for the Analysis of Medicines, Department of Pharmacy, Faculty of Medicine, CIRM, University of Liege, Avenue Hippocrate 15, B36, +3, Tower 4, 4000, Liege, Belgium. Electronic address: marianne.fillet@ulg.ac.be.

PMID: 29910088
DOI: 10.1016/j.chroma.2018.06.030

Abstract

A targeted CE-MS approach was developed for the chiral analysis of biologically relevant amino acids in artificial cerebrospinal fluid (aCSF). In order to achieve chiral resolution, the five amino acids (Ser, Asn, Asp, Gln and Glu) were derivatized with (+)-1-(9-fluorenyl)ethyl chloroformate ((+)-FLEC). The diastereoselectivity was found to be highly dependent on pH for all analytes and the optimized background electrolyte (BGE) consisted of 150 mM acetic acid, adjusted to pH 3.7 with NH₄OH. Furthermore, a reversal of the migration order of Asp derivatives was observed. This phenomenon seems to be caused by intra-molecular interactions affecting the pK_a of the second ionizable group (the side chain carboxyl). The applicability of this method was evaluated using aCSF. A solid phase extraction (SPE) protocol was developed for the selective extraction of the FLEC derivatives. A full evaluation of the matrix effect and extraction yield was performed concluding that the matrix effect is marginal and the recoveries are between 46 and 92%. The method offers adequate sensitivity (limits of detection below 1 μM).

Keywords: Amino acids; Chiral separations; Derivatization; FLEC; Migration order reversal.

MeSH terms

Amino Acids / chemistry*
Cerebrospinal Fluid / metabolism*
Electrolytes / chemistry
Electrophoresis, Capillary / methods*
Hydrogen-Ion Concentration
Mass Spectrometry / methods*
Metabolomics*
Solid Phase Extraction
Stereoisomerism

Substances

Amino Acids
Electrolytes