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Open tubular CEC in a microfluidic chip for rapid chiral recognition.

Chiral recognition of dansyl enantiomeric amino acids by microfluidic open tubular CEC (muOTCEC) with fluorescence detection was demonstrated. Avidin was employed as the chiral selector immobilized on the microchannel wall, which functioned as the chiral stationary phase (CSP) by physical adsorption. The condition of CSP on the glass wall was characterized using field emission SEM. Results indicated that avidin was homogenously distributed on the microchannel surface. Two parameters that played essential roles in muOTCEC for chiral recognition were investigated. Buffer pH could greatly change the amount of adsorption of avidin on the channel wall by altering the electrostatic attraction between them. Methanol, the organic additive to the running buffer, was also found significant for controlling the quality of the muOTCEC chiral separation by regulating the hydrophobic interaction between the enantiomers and the CSP. Under the optimized conditions, four dansyl racemic amino acids were then successfully separated by muOTCEC within 100 s with resolutions of 2.43, 1.88, 3.01 and 2.65 for dansyl-Ser, dansyl-Met, dansyl-Thr and dansyl-Val, respectively. Furthermore, a comparison with microfluidic CZE was investigated demonstrating that muOTCEC was a promising method for rapid chiral recognition.