Carr Research Group

Education: B.S., University of Dayton, 1997

Honors and Membership: Golden Key Honor Society, ACS, Magna Cum Laude Graduate,
BPTI Fellowship Recipient; American Chemical Society Member; Materials Research Society Member

Teaching Experience: Instrumental Analysis Lecture, Instrument Analysis Lab, Instrument Analysis Lab for Chemical Engineers; Separation Science.

Publications:

1. Trammell, B.C., Hillmyer, M.A., Carr, P.W., A Study of the Lewis Acid-Base Interactions of Vinylphosphonic Acid Modified Polybutadiene-coated Zirconia. Analytical Chemistry, 2001, 73, 3323 - 3331.

2. Trammell, B.C., Ma, L., Luo, H., Jin, D., Hillmyer, M.A., Carr, P.W., Highly Crosslinked Self-Assembled Monolayer Stationary Phases: A New Approach for Greatly Enhancing the Low pH Stability of RPLC Silica. Analytical Chemistry, 2002, accepted

Presentation:

1. Trammell, B.C., Hillmyer, M.A., Carr, P.W., Highly Crosslinked Self-Assembled Monolayer Stationary Phases: A New Approach for Greatly Enhancing the Low pH Stability of RPLC Silica. The Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, New Orleans, LA , March 2002, Oral Presentation.

2. Trammell, B.C., Hillmyer, M.A., Carr, P.W., A Study of the Lewis Acid-Base Interactions of Vinylphosphonic Acid Modified Polybutadiene-coated Zirconia. HPLC 2001 Conference, Maastricht, The Netherlands, June 2001, Poster Presentation.

3. Trammell, B.C., Hillmyer, M.A., Carr, P.W., Novel Approaches for Blocking the Lewis Acidity of Polybutadiene-coated Zirconia. The Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, New Orleans, LA , March 2001, Oral Presentation.

4. Trammell, B.C., Hillmyer, M.A., Carr, P.W., A New Approach to Reversed Phase Materials on Zirconia for Improved Chromatography of Lewis Bases. Materials Research Society Spring Symposium, San Francisco, CA, May 2000, Oral Presentation.

Research Project Description:

1. The tremendous structural diversity of polymers makes them attractive for developing highly selective phases for HPLC. By coating and crosslinking a polymer on an inorganic support, the problems associated with swelling and microporosity of pure polymeric phases are greatly diminished. Non-polar polymers coated on zirconia are very stable RPLC media. The advantages of using polymer-coated metal oxides are tempered by difficulties in achieving coating homogeneity. Conventional liquid phase deposition techniques produce phases with less than 60% coverage of the problematic Lewis acid sites on zirconia. This leads to poor efficiency and peak tailing of Lewis base analytes. Additionally and more generally, coating heterogeneity limits stationary phase mass transfer and consequently the theoretical efficiency (h=2-3) can only be achieved at very low ( 3-4% w/w) polymer load.
In order to overcome the intractable limitations of direct polymer coating from the liquid phase, zirconia will be coated by a novel "umbrella" technique. First, the Lewis acid sites will be maximally sequestered by exhaustively chemisorbing a crosslinkable, hard Lewis base monomer (e.g. vinylphosphonic acid). Second, a crosslinked polymer network or "umbrella" which incorporates the sequestrant will be formed in vacuo on the surface. Both the incorporated Lewis sequestrant and the polymer "umbrella" act to completely block the surface Lewis acid sites. Additionally, this coating method will ensure that the polymerization is confined to a very thin layer (a few monolayers of monomer). The polymer network will be effectively anchored to the surface through the chemisorbed sequestrant. The figures given below describe the methods currently being investigated.

2. Microparticulate silica is the most widely used substrate for RPLC stationary phases. Silica is an attractive support for many reasons. First, the particles are monodisperse, mechanically strong, and they have a high surface area and easily tailored pore size distributions. Second, a wide variety of commercially available silanes allows for covalent bonding to the surface, thus offering a diverse suite of chromatographic selectivities. The utility of silica-based stationary phases is limited by poor chemical stability at low and high pH. Stationary phase bleed at low pH and silica dissolution at high pH seriously inhibit the use of aggressive mobile phases for the separation of difficult analytes such as basic drugs.
To simultaneously address both the low and high pH stability problem, we investigated a multi-layer, two-dimensional polymerization method for modifying the silica surface. The first step in the modification is the formation of a dense self-assembled monolayer of chloromethylphenylethyltrichlorosilane. This monolayer provides 7.8 micromoles/m2 of reactive chlorine on the silica surface and is the basis for further treatment by Friedel-Crafts catalyzed self-condensation and crosslinking with additional reagents. In the second step, a crosslinkable aromatic compound and AlCl3 are used to extensively crosslink the self-assembled phenyl rings. The highly crosslinked phase is extremely stable under highly acidic mobile phase conditions. The pH stability of this crosslinked phase will be compared to other stable phases at low and high pH to demonstrate its extreme stability. Additionally, peak shape and efficiency for basic pharmaceuticals at low pH will be compared to commercial phases.

Email: trammell@chem.umn.edu

Address: 321 Smith Hall

Phone: (612) 624-5870

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