Professor Robert C. Dunn Named as Recipient of March 2026 Sutton Family Research Impact Award
The Department of Chemistry congratulates Professor Robert C. Dunn on receiving the March 2026 Sutton Family Research Impact Award!
The Sutton Award is a monthly competition among chemistry faculty. Every month, the Chemistry Department Chair and Associate Chairs review the peer-reviewed papers published by chemistry faculty from the three previous months to select a winner. The recipient receives a $500 cash prize and is featured on the departmental website.
For a full list of winners, visit our Sutton Family Research Impact Award webpage.
Tuning Apparent Peak Efficiency in Capillary Electrophoresis Using Backscatter Interferometry Detection
By Miyuru De Silva, Stanslaus M. Kariuki, and Robert C. Dunn
Electrophoresis, 47(1), 13-21 (2026), DOI 10.1002/elps.70059
Capillary electrophoresis (CE) is an inexpensive analytical separation technique that enables rapid analysis of complex mixtures. In CE, analytical separations are carried out in a small-bore capillary using a high voltage to separate ions based on their differing electrophoretic mobilities. To detect the separating species, our group has been developing a label-free approach based on refractive index (RI) changes. Since changes in solution composition influence the RI, separating bands can be detected using this approach. One advantage of RI detection is that it is a universal detector, capable of detecting all separating species from small inorganic ions to large proteins. A disadvantage is its limited detection limits. Much of our work, therefore, has focused on improving detection limits.
One way to improve detection limits is to exploit the well-known temperature sensitivity of RI using photothermal enhancement. In photothermal enhancement, migrating analytes are resonantly excited using a separate laser beam. As the excited analytes relax back to the ground state, they release heat into their surroundings which enhances the RI signal. In a previous report, we showed that this photothermal enhancement mechanism can improve detection limits by three orders of magnitude.
In this study, we exploited an interesting peak narrowing effect associated with photothermal enhancement to improve separation efficiency. In all separations, narrow peaks are desirable to resolve closely migrating species. In RI detection, analyte signals can be positive or negative depending on the analyte and the surrounding buffer. Using photothermal enhancement, positive going peaks just grow in magnitude while negative going peaks initially lose amplitude before changing sign and growing in the positive direction. For peaks changing sign, we showed that there is an interesting peak narrowing effect that occurs right at the transition. For example, peaks 4 and 5 in the electropherograms shown below for rhodamine 123 and rhodamine 6G, respectively, significantly narrow upon selective photothermal excitation using two laser beams as indicated. To illustrate the magnitude of this effect, we showed that peak efficiency, which is related to the width of the analyte bands, can increase from ~150,000 plates/m to well over ~2.5 million plates/m using this approach! We discussed the mechanism of this effect and demonstrated how this and a related effect arising from the separation voltage can significantly improve separations for closely migrating species.
