Chiral Separations by Temperature Gradient Focusing

Karin M. Balss, Wyatt N. Vreeland, Karen W. Phinney, Michael J. Tarlov, and David Ross

Process Measurements and Analytical Chemistry Divisions, Chemical Science and Technology Laboratory

National Institute of Standards and Technology, Gaithersburg MD 20899

Temperature gradient focusing (TGF) involves application of a temperature gradient across a microchannel or capillary. With an appropriate buffer, the temperature gradient creates a gradient in both the electric field and the electrophoretic velocity. Ionic species will then be stationary and concentrated at a unique point where the total velocity sums to zero. This is accomplished by balancing the electrophoretic velocity against the bulk flow of a temperature dependent buffer. TGF is capable of focusing any charged species and has been demonstrated with a wide variety of analytes ranging from small dye molecules to polymeric particles. In this work, the capabilities of TGF have been extended to include focusing and separation of chiral molecules. Specifically, cyclodextrins, which are popular chiral selectors used in capillary electrophoresis, are added to the TGF buffer and cause the two stereoisomers of a chiral molecule to focus at different points in the capillary. Figure 1 is a fluorescence micrograph illustrating the near baseline resolution of D- and L-glutamic acid. Studies are underway examining the analytical figures of merit for chiral TGF of D-, L-amino acids as well as small chiral drug molecules.

Balss Fig.1
Figure 1. Fluorescence micrograph of dansylated D, L glutamic acid in 1 m Tris(hydroxymethyl) aminomethane 1m boric acid buffer and 20 mm gCD. Focusing conditions, -1000 V cm-1, temperature gradient 20 ° C (right) to 60 ° C (left). For scale the image is 2 mm long.

Author Information:

Karin Balss

Process Measurements Division

Chemical Science and Technology Laboratory

Physics B324


Phone 975-2957

Fax 975-2643

Sigma Xi member- NO

Poster Category: Chemistry