Temperature gradient focusing for microchannel separations

The use of temperature gradient focusing (TGF) which is based upon balancing analytes electrophoretic mobilities for microfluidic separation, amino acids, small dye molecule separation was investigated. The counter-flow gradient focusing methods such as EEGF and TGF work by balancing the electrophoretic motion of analyte molecules against the bulk flow of solution through a separation channel. The TGF the electrophoretic velocity gradient was established by applying a temperature gradient along the length of the channel. The initial report on TGF includes a demonstration of the focusing of carboxyfluorescein using a temperature gradient induced by the internal Joule heating. One of the limitations of TGF and other counter-flow gradient focusing techniques was observed as limited peak capacity. In addition to increasing peak capacity the use of scanning TGF also allows for more reproducible and quantitative measurements with TGF.