Thermoswitchable Electrokinetic Ion-Enrichment/Elution Based on a Poly(N-isopropylacrylamide) Hydrogel Plug in a Microchannel

摘要

This paper reports a novel protocol consisting of thenthermomodulated electrokinetic enrichment, elution, andnseparation of charged species based upon a thermoswitchablenswelling-shrinking property of a poly(N-isopropylacrylamide),nPNIPAAm, hydrogel. A 0.2-1 mm longnPNIPAAm hydrogel plug was photopolymerized inside anglass microfluidic channel to produce a composite devicenconsisting of the PNIPAAm hydrogel plug and the glassnmicrochannel (abbreviated as plug-in-channel). After voltagenwas applied to the composite device, anions, such asnFITC, could be enriched at the cathodic end of thenPNIPAAm plug when the temperature of the plug was keptnbelow its lower critical solution temperature (LCST,n∼32 °C). The concentrated analytes could then be elutednby electroosmotic flow when the temperature of the plugnwas heated above the LCST. The mechanism of thenthermoswitchable ion enrichment/elution process wasnstudied with the results presented. The analytical potentialnof the composite device was demonstrated for the temperature-nmodulated preconcentration, elution, and separationnof FITC-labeled amino acids.