Enantiomeric separation of chiral dipeptides by CE-ESI-MS employing a partial filling technique with chiral crown ether.
Enantiomer of chiral dipeptides were separated by CE-ESI-MS in a bare fused-silica capillary using (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18C6H4) as the chiral selector. As 18C6H4 is a kind of nonvolatile chiral selector, in order to prevent from 18C6H4 into the ion-source of CE-ESI-MS, a partial filling technique was employed in this study. Some dipeptides with one chiral center or two chiral centers, such as DL-Leu-DL-Leu, D-Ala-D-Ala and L-Ala-L-Ala, Gly-D-Phe and Gly-L-Phe were used to evaluate this CE-ESI-MS system. Optimized conditions were achivevd with 2.0 mol/L acetic acid (pH 2.15) as the running electrolyte, 5 mM 18C6H4 in 3.0 mol/L acetic acid (pH 2.00) was injected hydrodynamically (50 mbar for 960 s) before sample injection. In total 7.5 mM acetic acid in 80% v/v methanol-water was used as the sheath liquid, and 20 kV applied voltage was used. Under the optimum conditions, these dipeptides were separated and detected. LODs (defined as S/N=3) of this method were 0.20, 0.10, 0.05 and 0.10 micromol/L for D-Ala-D-Ala, L-Ala-L-Ala, DL-Leu-DL-Leu, Gly-L-Phe and Gly-D-Phe, respectively. The RSDs (n=7) of the method were 0.68-2.08% for migration times and 2.32-5.24% for peak areas. The proposed method was also successfully applied to the enantioselective analysis of these dipeptides in the spiked serum samples with satisfactory results.
Xia
Shifei
S
Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, Department of Chemistry, Fuzhou University, Fuzhou, Fujian, P. R. China.
Zhang
Lan
L
Lu
Minghua
M
Qiu
Bin
B
Chi
Yuwu
Y
Chen
Guonan
G
D043844:Crown Ethers / Q000737:chemistry*; D004151:Dipeptides / Q000097:blood*; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D015203:Reproducibility of Results; D012822:Silicon Dioxide / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism
D043844:Crown Ethers; D004151:Dipeptides; D012822:Silicon Dioxide