TY - JOUR
T1 - Chiral capillary electrophoresis with UV-excited fluorescence detection for the enantioselective analysis of 9-fluorenylmethoxycarbonyl-derivatized amino acids
AU - Prior, Amir
AU - Coliva, Giulia
AU - de Jong, Gerhardus J.
AU - Somsen, Govert W.
PY - 2018/8
Y1 - 2018/8
N2 - The potential of capillary electrophoresis (CE) with ultraviolet (UV)-excited fluorescence detection for sensitive chiral analysis of amino acids (AAs) was investigated. dl-AAs were derivatized with 9-fluorenylmethoxycarbonyl chloride (FMOC)-Cl to allow their fluorescence detection and enhance enantioseparation. Fluorescence detection was achieved employing optical fibers, leading UV excitation light (< 300 nm) from a Xe-Hg lamp to the capillary window, and fluorescence emission to a spectrograph equipped with a charge-coupled device (CCD). Signal averaging over time and emission wavelength intervals was carried out to improve the signal-to-noise ratio of the FMOC-AAs. A background electrolyte (BGE) of 40 mM sodium tetraborate (pH 9.5), containing 15% isopropanol (v/v), 30 mM sodium dodecyl sulfate (SDS), and 30 mM β-cyclodextrin (β-CD), was found optimal for AA chemo- and enantioseparation. Enantioresolutions of 1.0 or higher were achieved for 16 proteinogenic dl-AAs. Limits of detection (LODs) were in the 10–100-nM range (injected concentration) for the d-AA enantiomers, except for FMOC-d-tryptophan (536 nM) which showed intramolecular fluorescence quenching. Linearity (R2 > 0.997) and repeatability for peak height (relative standard deviations (RSDs) < 7.0%; n = 5) and electrophoretic mobility (RSDs < 0.6%; n = 5) of individual AA enantiomers were established for chiral analysis of dl-AA mixtures. The applicability of the method was investigated by the analysis of cerebrospinal fluid (CSF). Next to l-AAs, endogenous levels of d-glutamine and d-aspartic acid could be measured in CSF revealing enantiomeric ratios of 0.35 and 19.6%, respectively. This indicates the method’s potential for the analysis of low concentrations of d-AAs in presence of abundant l-AAs.
AB - The potential of capillary electrophoresis (CE) with ultraviolet (UV)-excited fluorescence detection for sensitive chiral analysis of amino acids (AAs) was investigated. dl-AAs were derivatized with 9-fluorenylmethoxycarbonyl chloride (FMOC)-Cl to allow their fluorescence detection and enhance enantioseparation. Fluorescence detection was achieved employing optical fibers, leading UV excitation light (< 300 nm) from a Xe-Hg lamp to the capillary window, and fluorescence emission to a spectrograph equipped with a charge-coupled device (CCD). Signal averaging over time and emission wavelength intervals was carried out to improve the signal-to-noise ratio of the FMOC-AAs. A background electrolyte (BGE) of 40 mM sodium tetraborate (pH 9.5), containing 15% isopropanol (v/v), 30 mM sodium dodecyl sulfate (SDS), and 30 mM β-cyclodextrin (β-CD), was found optimal for AA chemo- and enantioseparation. Enantioresolutions of 1.0 or higher were achieved for 16 proteinogenic dl-AAs. Limits of detection (LODs) were in the 10–100-nM range (injected concentration) for the d-AA enantiomers, except for FMOC-d-tryptophan (536 nM) which showed intramolecular fluorescence quenching. Linearity (R2 > 0.997) and repeatability for peak height (relative standard deviations (RSDs) < 7.0%; n = 5) and electrophoretic mobility (RSDs < 0.6%; n = 5) of individual AA enantiomers were established for chiral analysis of dl-AA mixtures. The applicability of the method was investigated by the analysis of cerebrospinal fluid (CSF). Next to l-AAs, endogenous levels of d-glutamine and d-aspartic acid could be measured in CSF revealing enantiomeric ratios of 0.35 and 19.6%, respectively. This indicates the method’s potential for the analysis of low concentrations of d-AAs in presence of abundant l-AAs.
KW - Amino acids
KW - Capillary electrophoresis
KW - Cerebrospinal fluid
KW - Chiral separation
KW - Fluorescence detection
KW - FMOC derivatization
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U2 - 10.1007/s00216-018-1148-x
DO - 10.1007/s00216-018-1148-x
M3 - Article
AN - SCOPUS:85047664107
VL - 410
SP - 4979
EP - 4990
JO - Analytical and Bioanalytical Chemistry
JF - Analytical and Bioanalytical Chemistry
SN - 1618-2642
IS - 20
ER -