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Thesis defences

PhD Oral Exam - John Chin, Chemistry

Independent Parallel Capillary Array Separations for Rapid Second Dimension Sampling in On-Line Two-Dimensional Capillary Electrophoresis of Complex Biological Samples

Friday, July 17, 2020
1:30 p.m. – 4:30 p.m.

This event is free


School of Graduate Studies


Daniela Ferrer



When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.


Biological samples remain challenging in proteomic separations due to their complexity and large concentration dynamic range. Improvements to separation power are needed to interrogate proteomes more deeply and facilitate the advancement of biomarker discovery for personalized medicine.

Current online multidimensional separations require compromise; long analysis times if the second dimension (2D) must be regenerated between injections, or reduced separation efficiency if the 2D is operated rapidly. Using an array of capillaries as the 2D, operated in parallel, allows fast sampling of the first dimension (1D). This relaxes the constraints on the 2D separation, allowing it to operate at optimal separation conditions that would otherwise be sacrificed for speed. This schema allows total separation times to approximately equal to the 1D separation time.

We have developed a novel interface that enables continuous sampling of a 1D separation by a 2D capillary array for rapid, high peak capacity two dimensional (2D) separations. Based upon automated precision positioning of capillaries in a laminar flow regime, a capillary electrophoresis (CE) 1D separation was coupled to an array of eight independent CE 2D separations. The instrument terminus provides laser induced fluorescence detection via a sheath flow cuvette.

Effluent transfer efficiency and detection was optimized using visible and fluorescent dye tracers. To that end, this dissertation will discuss characterization of interface and detector parameters, including: inter capillary transverse alignment accuracy, injection distance, injection time, hydrodynamic flow rate, density considerations, inter and intra capillary differences, signal crosstalk and laser intensity.

Separation performance will further be demonstrated using model protein and serum digestates. Each dimension of the 2D instrument will be operated as a one dimensional (1D) instrument to compare against an optimized commercial 1D CE instrument. These results will be used to evaluate the quality of the separations operated in on line 2D capillary electrophoresis-to-capillary array electrophoresis (CE×CAE) mode. A novel application of the CE×CAE design will be discussed in the spirit of resolving the long standing challenge of migration time reproducibility in CE separations.

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