title: Enantioselective analysis of proteinogenic amino acids in cerebrospinal fluid by capillary electrophoresis-mass spectrometry.
abstract: d-Amino acids (AAs) are increasingly being recognized as essential molecules in biological systems. Enantioselective analysis of proteinogenic AAs in biological samples was accomplished by CE-MS employing β-CD as chiral selector and ESI via sheath-liquid (SL) interfacing. Prior to analysis, AAs were fully derivatized with FMOC, improving AA-enantiomer separation and ESI efficiency. In order to optimize the separation and MS detection of FMOC-AAs, the effects of type and concentration of CD in the BGE, the composition of the SL, and MS-interfacing parameters were evaluated. Using a BGE of 10 mM β-CD in 50 mM ammonium bicarbonate (pH 8) containing 15% v/v isopropanol, a SL of isopropanol-water-1 M ammonium bicarbonate (50:50:1, v/v/v) at a flow rate of 3 μL/min, and a nebulizer gas pressure of 2 psi, 15 proteinogenic AAs could be detected with enantioresolutions up to 3.5 and detection limits down to 0.9 μM (equivalent to less than 3 pg AA injected). The selectivity of the method was demonstrated by the analysis of spiked cerebrospinal fluid, allowing specific detection of d-AAs. Repeatability and linearity obtained for cerebrospinal fluid were similar to standard solutions, with peak area and migration-time RSDs (n = 5) below 16.2 and 1.6%, respectively, and a linear response (R(2) ≥ 0.977) in the 3-90 μM range.
authors.affiliation: Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands. a.prior@vu.nl.
authors.forename: Amir
authors.initials: A
authors.lastname: Prior
authors.affiliation: Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Universidad de Alcalá, Alcalá de Henares (Madrid), Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Sánchez-Hernández
authors.affiliation: Division of Biomolecular Analysis, Utrecht University, CG Utrecht, The Netherlands.
authors.forename: Javier
authors.initials: J
authors.lastname: Sastre-Toraño
authors.affiliation: Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Universidad de Alcalá, Alcalá de Henares (Madrid), Spain.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Marina
authors.affiliation: Division of Biomolecular Analysis, Utrecht University, CG Utrecht, The Netherlands.
authors.forename: Gerhardus J
authors.initials: GJ
authors.lastname: de Jong
authors.affiliation: Division of BioAnalytical Chemistry, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
authors.forename: Govert W
authors.initials: GW
authors.lastname: Somsen
mesh_terms: D000596:Amino Acids / Q000134:cerebrospinal fluid*; D019075:Electrophoresis, Capillary / Q000379:methods*; D057230:Limit of Detection; D013058:Mass Spectrometry / Q000379:methods*; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids
keywords: Amino acids; Capillary electrophoresis-mass spectrometry; Cerebrospinal fluid; Chiral separation