Kurt Hoeman

Electrokinetic trapping using titania nanoporous membranes fabricated using sol-gel chemistry on microfluidic devices.

We have developed a new method for analyte preconcentration on a microfluidic device using a porous membrane fabricated via sol–gel chemistry. These porous membranes were fabricated within the channels of glass microfluidic devices exploiting laminar flow to bring an alcoholic sol–gel precursor (titanium isopropoxide in 2‐propanol) into contact with an alcohol–water solution at a channel cross intersection. These two streams reacted at the fluidic interface to form a porous titania membrane. The thickness of the membrane could be altered by changing the [H2O]. Analyte concentration was accomplished by applying a voltage across the titania membrane. The level of analyte enrichment was monitored, and enrichment factors of above 4000 in 400 s were obtained for 2,7‐dichlorofluorescein.

A novel, environmentally friendly sodium lauryl ether sulfate-, cocamidopropyl betaine-, cocamide monoethanolamine-containing buffer for MEKC on microfluidic devices.

A new buffer has been developed for fast, high‐efficiency separations of amino acids by MEKC. This buffer was more environmentally friendly than the most commonly used surfactant‐containing buffers for MEKC separations. It used a commercially available dishwashing soap by Seventh Generation™ (Burlington, VT, USA), which contained three micelle‐forming agents. The mixed micelles were composed of sodium lauryl ether sulfate (anionic), cocamidopropyl betaine (zwitterionic), and cocamide monoethanolamine (non‐ionic). The optimized buffer contained 5.0% w/w Seventh Generation™ Free & Clear™ dishwashing soap, 10 mM sodium borate, and was completely void of organics. The lack of organics and the biodegradability of the surfactant molecules made this buffer more environmentally friendly than typical SDS‐containing buffers. This new buffer also had a different selectivity and provided faster separations with higher separation efficiencies than SDS‐based buffers. Fast separations of BODIPY FL labeled amino acids yielded peaks with separation efficiencies greater than 100 000 in less than 20 s.