Professor Susan Jansen-Varnum Research Interests

Analysis of Pharmaceuticals and Medical Devices

Combination drugs, chiral drugs and drug degradation all required sophisticated analytical assays. Combination drugs contain two or more active species, the active species are typically imported from large manufacturing facilities and need purity assays for qualifications. Preservatives, flavorings and other inactive components are included in the formulation. Assays must identify and quantify all species regardless of chemical nature, quantity and complexity. These can be challenging endeavors. Many active pharmaceuticals are chiral compounds. However, drug substances can be distributed as racemic mixtures or pure enantiomers. In either case, assays must be developed that discriminated and quantify the enantiomeric distribution accurately.

Orthopedic materials are used in many applications including vertebraplasty, kyphoplasty, craniaplasty and screw augmentation. To qualify materials for use formulation assays, analysis of leachables and cytotoxicity must be performed. In almost all cases HPLC and LC-MS is used to identify all species in bone cements, scaffolding devices and bone implant materials.

The Role of Humic Acid in the Environment

Humic substances (HS) are essential but incompletely understood sorptive and metal binding biopolymers in animals, plants, soils and sediments. HS continue to be intensively studied because of their environmental importance. HS have important physiological properties, many of which are attributed to their sorptive properties. HA can bind heavy metals in vivo, reducing toxicity. Polyaromatic hydrocarbons, pesticides and viral particles adsorb on HS surfaces. Heparin-like activity has been identified for soil derived HA. HA is therapeutic against goiter and uterine cancer in laboratory animals, suggesting similar receptor binding characteristics. HA is found in and near lung tumors in coal miners and smokers suggesting a possible link between HA and tumorogenesis.

Our studies on HA show that HA is a powerful reductant and an excellent chelating agent. The combination of these effects creates a chemical systems that can activate transition metals. For example ferric iron is chelated and reduced to ferrous iron. The ferrous iron in the HA matrix can then participate in a variety of Fenton chemistries. The effects are similar for copper and a variety of transition metals. This reductive chelation provides for a variety of important reaction chemistries.

Electronic Materials: PAni, Keggin Ions and Li-Batteries

New materials have been developed for lithium batteries to improve the performance of batteries. In the market, the common materials for cathode of batteries are Li(1-x)NiO2, Li(1-x)CoO2, Li(1-x)Mn2O4. These materials have ability of intercalate and deintercalate rapidly and reversibly into the cathode during repeated discharge and charge cycles when Li+ ions released from the anode into the electrolyte solution. Many studies indicated that V2O5 xerogel films is the best of efficient and reversible insertion of Li+ ion at high potentials compare to Li, thus resulting in high specific capacity and energy density. The advantage of this material is very easy to synthesis. However, this material has a low electronic conductivity, a relatively low Li+ diffusion coefficient within the host matrix, and capacity fade during repeat charge and discharge cycles because of irreversible structural changes induced by redox cycling. Some experiments found that doping vanadium oxide xerogels with silver, the electronic conductivity increased. In fact, 0.1 mole of silver per mole of V2O5 with intermediate doping levels, the conductivity was enhanced by a factor of 80 without any significant change in the host layered structure. Other experiments have shown that added a conducting polymers increases conductivity. A tenfold enhanced diffusion coefficient for Li+ in polyaniline (PANI) mixed with V2O5 has been reported. The advantages of PANI are environmental stability, controllable electrical conductivity, and easy process ability. PANI may also have applications for Li ion rechangeable battery, electrode of light emitting diode, corrosion protection, RF and microwave absorber and antistatic materials. Polyaniline also can increase porosity, surface area and Li+ adsorption capacity, so the consequence is increasing the ability of lithium intercalation for a new type composite carbonaceous anode electrode, if composite carbonaceous electrode fabricate with ceramic and polyaniline fillers. Our work uses a oligomer of PAni which offers the high conductivity necessary without the processing issues associated with the polymeric form.

Vanadium-Substituted Keggin Ion

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