Chiral silanes (non-superimposable mirror image isomers) are of interest in current research in pharmaceutical studies and as chiral derivatization agents in organic synthesis.  However, the enantiomers of many of these chiral silanes are difficult to separate by traditional chiral liquid chromatography methods, making enantiomeric excess determinations difficult. Capillary electrophoresis is an attractive alternative method due to its high analysis speed, flexible methodology, and low sample/solvent consumption.  In capillary electrophoresis, analytes are separated within a small silica capillary filled with an aqueous buffer solution by an applied electric field (Figure 1).  The separation may be optimized by altering the buffer conditions and by introducing various additives.  In this study, we are developing methods of micellar electrokinetic chromatography (MEKC) to achieve enantioseparation of novel synthesized chiral silanes. Various β-cylcodextrin derivatives and chiral surfactants are evaluated for their enantioselectivity.

Figure 1. Top: Diagram illustrating free solution capillary electrophoresis separation of ions and neutral compounds;  Bottom: Diagram showing the equilibria of a solute molecule (red sphere) with a cyclodextrin and micelle in CD-MCE.

Capillary isoelectric focusing (CIEF) is a mode of capillary electrophoresis that utilizes a pH gradient to focus and separate analytes by their pI values (Figure 2).  A mobilization step is then used to sweep the focused analytes past a detector for quantitation.  CIEF may be used for any ionizable analyte, however it is most commonly used for the analysis of large polyvalent molecules, such as proteins.  Our lab is currently developing a CIEF method for the separation and quantitation of phosphorylated and non-phosphorylated GAP-43 protein.  GAP-43 protein is a nervous system membrane protein that plays a key role in neurite growth and plasticity.  The relative degree of phosphorylation of GAP-43 may be correlated to neuro-degenerative diseases.  CIEF may also be used for the focusing and analysis of microorganisms by exploiting differences in the cells’ surface charge pIs.  Current methods for identifying bacteria and fungi contamination in food, water, and medical samples are lacking in numerous aspects- mainly time, cost, and detection ability.  Many of these shortcomings may potentially be resolved using alternative techniques such as CIEF.  Our current work focuses on both the detection of cells in a sample and also the physical separation of cells (by species or other physical properties) in a manner similar to that of a molecular separation.

Figure 2. Isoelectric focusing in a fused silica capillary.

Redox flow cell batteries are a possible option in future, large scale energy storage systems. Because of the variable output of alternative energy sources (e.g., wind, solar) a means of mass energy storage is necessary for the power grid. In this research, we aim to develop a fully organic flow cell battery employing quinone derivatives as active redox agents. Quinone compounds are of particular interest because they are naturally occurring redox agents and can be used in more environmentally friendly conditions than traditional electrolytes. Our lab is synthesizing various novel quinone derivatives to modify their electrochemical characteristics and solubility.  Cyclic voltammetry may be used to assess their reduction potentials, redox reversibility, kinetics, and other electrochemical characteristics. Pairs of compounds that display large differences in reduction potential and show rapid electron transfer kinetics may be then chosen as potential electrolytes for testing in our prototype flow cell (Figure 3). These pairs are tested over multiple charge and discharge cycles to assess their energy storage efficiency, current densities, and voltage discharge profiles.

Figure 3. Prototype flow cell test bed.

Flaherty, R. J., Nshime, B., DeLaMarre, M., DeJong, S., Scott, P., & Lantz, A. (2013). Cyclodextrins as Complexation and Extraction Agents for Pesticides from Contaminated Soil. Chemosphere, 91, 912-920

Lantz, A., Bisha, B., Tong, M.-Y., Nelson, R. E., Brehm-Stecher, B. F., & Armstrong, D. W. (2010). Rapid Identification of Candida albicans in Blood by Combined Capillary Electrophoresis and Fluorescence in situ Hybridization. Electrophoresis, 31, 2849-2853

Lantz, A., Brehm-Stecher, B. F., & Armstrong, D. W. (2008). Combined Capillary Electrophoresis and DNA-FISH for Rapid Molecular Identification of Salmonella Typhimurium in Mixed Culture. Electrophoresis (29), 2477-2484

Lantz, A., Bao, Y., & Armstrong, D. W. (2007). Single Cell Detection: A Rapid Test of Microbial Contamination Using Capillary Electrophoresis. Analytical Chemistry (79), 1720-1724

Lantz, A., Pino, V., Anderson, J. L., & Armstrong, D. W. (2006). Determination of Solute Partition Behavior with Room-Temperature Ionic Liquid Based Micellar Gas–Liquid Chromatography Stationary Phases using the Pseudophase Model. Journal of Chromatography A (1115), 217-224

Lantz, A., Rodriguez, M. A., Wetterer, S. M., & Armstrong, D. W. (2006). Estimation of Association Constants Between Oral Malodor Components and Various Native and Derivatized Cyclodextrins. Analytica Chimica Acta (557), 184-190

Pino, V., Lantz, A., Anderson, J. L., Berthod, A., & Armstrong, D. W. (2006). Theory and Use of the Pseudophase Model in Gas-Liquid Chromatographic Enantiomeric Separations. Analytical Chemistry (78), 113-119

Lantz, A., Rohzkov, R. V., Larock, R. C., & Armstrong, D. W. (2004). Enantiomeric Separation of Neutral Hydrophobic Dihydrofuroflavones by Cyclodextrin-Modified Micellar Capillary Electrophoresis. Electrophoresis (25), 2727-2734