Highly sensitive chiral analysis of amino acids by in-line single drop microextraction and capillary electrophoresis with laser-induced fluorescence detection.
A highly sensitive method for chiral analysis of amino acids by in-line single drop microextraction (SDME) and chiral capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection was developed. In SDME, a drop of a basic aqueous acceptor phase covered with a thin organic layer was formed at the tip of a capillary by simple combination of sample-handling sequences of a CE apparatus. Then fluorescein isothiocyanate (FITC)-derivatized amino acids in an acidic donor solution were enriched into the drop through the organic layer. The enriched enantiomers were then resolved using a dual chiral selector of β-cyclodextrin (β-CD) and sodium taurodeoxycholate (STC). Here, in addition to serving as a labeling reagent providing high fluorescence signal, hydrophobic FITC was primarily used as a modifier aiding the extraction of zwitterionic amino acids by blocking the amino groups and increasing the hydrophobicity, yielding 220 times increase in extraction efficiency. Several hundred-fold enrichments were achieved with 10 min SDME, yielding LODs of 30-60 pM and enabling direct analysis of d-AAs in a 99% enantiomeric excess mixture. In view of no additional modification of the existing commercial CE instrument, this method without stirring can be easily realized using known operations. When a microstirrer was customized to the CE instrument several thousand-fold enrichments could be obtained with LODs in the low picomolar range of 1-3 pM.
Liang
Guodong
G
Department of Chemistry, Seoul National University, Seoul 151-747, Republic of Korea.
Choi
Kihwan
K
Badjah Hadj Ahmed
Ahmed Yacine
AY
ALOthman
Zeid A
ZA
Chung
Doo Soo
DS
D000596:Amino Acids / Q000032:analysis* / Q000302:isolation & purification; D019075:Electrophoresis, Capillary / Q000379:methods*; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D007834:Lasers; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013237:Stereoisomerism; D013657:Taurodeoxycholic Acid / Q000737:chemistry; D047392:beta-Cyclodextrins / Q000737:chemistry
D000596:Amino Acids; D047392:beta-Cyclodextrins; D013657:Taurodeoxycholic Acid; D016650:Fluorescein-5-isothiocyanate; C031215:betadex