title: Multidimensional separation of chiral amino acid mixtures in a multilayered three-dimensional hybrid microfluidic/nanofluidic device.
abstract: Microscale total analysis systems (microTAS) allow high-throughput analyses by integrating multiple processes, parallelization, and automation. Here we combine unit operations of microTAS to create a device that can perform multidimensional separations using a three-dimensional hybrid microfluidic/nanofluidic device composed of alternating layers of patterned poly(methyl methacrylate) and nanocapillary array membranes constructed from nuclear track-etched polycarbonate. Two consecutive electrophoretic separations are performed, the first being an achiral separation followed by a chiral separation of a selected analyte band. Separation conditions are optimized for a racemic mixture of fluorescein-isothiocyanate-labeled amino acids, serine and aspartic acid, chosen because there are endogenous D-forms of these amino acids in animals. The chiral separation is implemented using micellar electrokinetic chromatography using beta-cyclodextrin as the chiral selector and sodium taurocholate as the micelle-forming agent. Analyte separation is monitored by dual-beam laser-induced fluorescence detection. After separation in the first electrophoretic channel, the preselected analyte is sampled by the second-stage separation using an automated collection sequence with a zero-crossing algorithm. The controlled fluidic environment inherent to the three-dimensional architecture enables a series of separations in varying fluidic environments and allows sample stacking via different background electrolyte pH conditions. The ability to interface sequential separations, selected analyte capture, and other fluidic manipulations in the third dimension significantly improves the functionality of multilayer microfluidic devices.
authors.affiliation: Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Bo Young
authors.initials: BY
authors.lastname: Kim
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Maojun
authors.initials: M
authors.lastname: Gong
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Flachsbart
authors.forename: Mark A
authors.initials: MA
authors.lastname: Shannon
authors.forename: Paul W
authors.initials: PW
authors.lastname: Bohn
authors.forename: Jonathan V
authors.initials: JV
authors.lastname: Sweedler
mesh_terms: D000596:Amino Acids / Q000737:chemistry* / Q000302:isolation & purification*; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D007267:Injections; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D036103:Nanotechnology / Q000295:instrumentation*; D011076:Polycarboxylate Cement / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D011076:Polycarboxylate Cement; C005506:polycarbonate; D019904:Polymethyl Methacrylate; D016650:Fluorescein-5-isothiocyanate