Carr Research Group

Education: B.S., Zhongshan University; M.S., University of Texas at El Paso; Ph.D., Purfue University

Pulications:

1. D. Jin, H. L. Pardue "Algorithms for Time-dependent Chromatographic Peak Areas I. Algorithms Evaluated for Fully Resolved Peaks". Anal. Chim. Acta., 422, 1, 1-10;

2. D. Jin, H. L. Pardue "Algorithms for Time-dependent Chromatographic Peak Areas II. Resolution of Overlapped Chromatograms for Two- and Three-component samples". Anal. Chim. Acta., 422, 1, 11-20.

Research Project Description:

Chemically bonded RPLC stationary phases on silica are unstable at pH values below 2-3 and above 8-9 due to the hydrolytic instability of siloxane bonds and the solubility of silica in bases, respectively. Recent work in our laboratory demonstrates that the modification of silica surface with self-assembled, multilevel, 2-D polymerization approach can significantly improve both the acidic and basic column stability. In this novel approach, self-assembled chloromethylphenylethyl monolayer on silica surface is subjected to Friedel-Crafts self-condensation and cross-linking reactions with additional reagents. The additional polymeric barrier above the horizontal Si-O-Si bonds provides further protection to the surface from acid or base attack. To better understand the Friedel-Crafts reactions and to promote the maximum degree of cross-linking on the surface, kinetic studies of the reactions between the cross-linkers and chloromethyl groups on silica is needed.
In this work, we developed a reversed-phase HPLC method to investigate the reaction rates of surface chloromethyl species with several cross-linking reagents such as triphenylmethane (TPM) and diphenylmethane (DPM). The effects of the amount of Friedel-Crafts catalyst, the solvent, temperature, and self-condensation time prior to the cross-linking reaction are studied. Results show that TPM/DPM reacts rapidly with the surface in the presence of AlCl3. Self-condensation proceeds in parallel with the cross-linking reaction thereby competing with each other for active sites. The kinetics studies will guide the optimization of the crosslinking chemistry and thus of the surface modification.

Address: 317 Smith Hall

Phone: (612) 624-5870

Modified by Hao Luo --- hluo@chem.umn.edu