title: Mechanistic aspects in the generation of apparent ultrahigh efficiencies for colloidal (microbial) electrokinetic separations.
abstract: Under specific experimental conditions, the electrokinetic separation of certain microorganisms can produce peaks of very high apparent efficiencies (approximately 10(6)-10(10) theoretical plates/m). This is unusual in that no deliberate focusing mechanism was employed. To investigate this process further, the separation was monitored in real time using a charge-coupled device (CCD) imaging system. At least two different processes seem to be operative when these narrow peaks are observed. The initial field-induced association of cells appears to require a dilute polymer solution, electroosmotic flow (preferably countercurrent to the direction of cell electrophoresis), and a direct current electric field. Three possible models are presented that may explain aspects of the observed behavior. The balance between dispersive forces and intercellular adhesive forces also affects the observed bandwidths. Understanding and controlling the dynamic and aggregation of cells in microfluidic processes is essential, since it can be beneficial for some experiments and detrimental to others.
authors.affiliation: Department of Chemistry and Ames Laboratory-USDOE, Iowa State University, Ames 50011, USA.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Armstrong
authors.forename: Marco
authors.initials: M
authors.lastname: Girod
authors.forename: Lingfeng
authors.initials: L
authors.lastname: He
authors.forename: Michael A
authors.initials: MA
authors.lastname: Rodriguez
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Jinjian
authors.initials: J
authors.lastname: Zheng
authors.forename: Edward S
authors.initials: ES
authors.lastname: Yeung
mesh_terms: D001422:Bacterial Adhesion; D001644:Bifidobacterium / Q000166:cytology*; D003102:Colloids / Q000302:isolation & purification*; D019075:Electrophoresis, Capillary / Q000379:methods*; D008904:Miniaturization; D011092:Polyethylene Glycols / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000166:cytology*; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D003102:Colloids; D011092:Polyethylene Glycols