Jeffrey J. Rosentreter

Piezoelectric quartz crystal biosensors

Biosensing methods utilize the intrinsic selectivity of a biorecognition process to create relatively simple, low cost, analytical alternatives for a variety of research investigations. Here, biosensor applications of the piezoelectric quartz crystal (PQC) are reviewed. The discussion is divided into sections focusing on the development of PQC based analytical techniques, applications in solution phase sensing pertaining to PQC biosensors, and the current state of knowledge in PQC biosensing applications. Immobilization procedures, dip and dry assay techniques, and solution phase sensing methods are considered in detail.

A piezoelectric method for monitoring formaldehyde induced crosslink formation between poly-lysine and poly-deoxyguanosine.

To date, no experimental technique has been used to monitor DNA-protein crosslink formation in real-time. Real-time data is important for understanding the underlying chemical mechanisms associated with this reaction process. Here, the novel adaptation of existing piezoelectric quartz crystal (PQC) or quartz crystal microbalance (QCM) technology was used to monitor, in real-time, the formation of a crosslink bond induced by formaldehyde between lysine and guanine. Previous results showed complexes of lysine and guanine constitute a major portion of the DNA-protein crosslinks formed. Thus, poly-lysine(5) and poly-deoxyguanosine(11) were used as a model system to develop this detection method. Poly-lysine(5) was immobilized on QCM electrode surfaces by covalent attachment through polyethylenimine (PEI). Immobilization was confirmed by the decrease in dry QCM frequency; data consistency suggested uniform coatings were produced. The QCM sensor was configured within a thermostatic environmental chamber. The system was calibrated and baseline responses to variations in the analyte solution matrix were identified. QCMs with immobilized poly-lysine(5) were placed in contact with formaldehyde and poly-deoxyguanosine(11), and crosslink formation was monitored in real-time. Crosslink formation was verified through evaluation of controls. Control assays indicated some of the frequency signal was as aresult of non-specific association. Further assays were conducted after saturation of non-specific binding. This real-time data represents a significant advancement in the state of knowledge of the crosslinking process and provides the experimental foundation for further QCM crosslink investigations.

Chapter 7 – Uranium Sorption onto Natural Sands as a Function of Sediment Characteristics and Solution pH

Uranium sorption studies were conducted on twenty-five sandy sediments obtained from Virginia`s Easter Shore Peninsula using batch contact methods. Distribution coefficient (Kd) and sorption isotherms have been determined as function of solution pH. All sediment samples strongly sorbed dissolved uranium species at pH values above 5. Sediments characterized by high iron, aluminum, and surface area, possessed the highest sorption characteristics. Both, Freundlich and Dubinin Radushkevich equations were able to describe the sorption behavior. From the Dubinin-Radushkevich equation, the solution-component-solid surface bounding energy and the sorption capacities, were estimated. Least square regression utilizing sediment characteristics provided an effective statistical method for Kd prediction. Predictions with relative errors of about 30% were obtained using only two sediment variables, such as, iron or aluminum content and surface area. In conclusion, the results support that ion exchange and surface complexation reactions with the ferric and aluminum oxide/oxyhydroxides groups are the predominant sorption mechanisms.

The use of synthesized aqueous solutions for determining strontium sorption isotherms

The use of synthesized aqueous solutions for determining experimentally derived strontium sorption isotherms of sediment was investigated as part of a study accessing strontium chemical transport properties. Batch experimental techniques were used to determine strontium sorption isotherms using synthesized aqueous solutions designed to chemically represent water from a natural aquifer with respect to major ionic character and pH. A strontium sorption isotherm for a sediment derived using a synthesized aqueous solution was found to be most comparable to an isotherm derived using natural water when the synthesized aqueous solution contained similar concentrations of calcium and magnesium. However, it is difficult to match compositions exactly due to the effects of disequilibrium between the solution and the sediment. Strong linear relations between sorbed strontium and solution concentrations of calcium and magnesium confirm that these cations are important co-constituents in these synthesized aqueous solutions. Conversely, weak linear relations between sorbed strontium and solution concentrations of sodium and potassium indicate that these constituents do not affect sorption of strontium. The addition of silica to the synthesized aqueous solution does not appreciably affect the resulting strontium sorption isotherm.

Solvent selection for fatty acid residue analysis of archeologicial artifacts

Abstract Residue analysis has rapidly become one of the most useful techniques for determining an artifact function and revealing insight into paleodiets. The success of analytical residue analysis often lies with the first preparatory step, where the residue is extracted from the object. Detection of a residue requires effective solvation of the material, and there is a large range of potential solvents. One purpose of this study is to determine the efficiency of various solvents for the extraction of fatty acids from charcoal, a material that is ubiquitous, easily identified, remarkably stable in the archaeological record but, most importantly for this research, retains fats extremely well. This investigation examines the removal efficiency of model fatty acids from carbonized wood samples. The strong affinity of lipids to charcoal makes carbonized wood ideal for retaining them, but also makes their extraction extremely challenging and thus an ideal benchmark for solvent extraction characterization. Several solvents (benzene, chloroform, hexane, methanol and water) are used to determine the quantitative extraction efficiency of tripalmitin. While benzene and chloroform perform best for some wood types, neither solvent is better for all carbonized wood. Correlations between the chemical properties of the solvents and the effectiveness of the extraction provide guidance for solvents. Findings indicate solvent characteristics including dipole moment, dielectric constant, hydrogen bonding, and molecular weight all play an important role in extraction of fat from a charcoal matrix. Results presented should provide guidelines to allow for more effective residue extration and more accurate lipid analysis.

The Use of Chemical and Physical Properties for Characterization of Strontium Distribution Coefficients at the Idaho National Engineering and Environmental Laboratory, Idaho

The U.S. Geological Survey and Idaho State University, in cooperation with the U.S. Department of Energy, conducted a study to determine strontium distribution coefficients (Kds) of surficial sediments at the Idaho National Engineering and Environmental Laboratory (INEEL). Batch experimental techniques were used to determine experimental Kds of 20 surficial-sediment samples from the INEEL. The Kds describe the distribution of a solute between the solution and solid phase. A best-fit model was obtained using a four-variable data set consisting of surface area, manganese oxide concentration, specific conductance, and pH. Application of the model to an independent split of the data resulted in an average relative error of prediction of 20 percent and a correlation coefficient of 0.921 between predicted and observed strontium Kds. Chemical and physical characteristics of the solution and sediment that could successfully predict the Kd values were identified. Prediction variable select ion was limited to variables which are either easily determined or have available tabulated characteristics. The selection criterion could circumvent the need for time- and labor-intensive laboratory experiments and provide an alternate faster method for estimating strontium Kds.

Strontium distribution coefficients of surficial sediment samples from the Idaho National Engineering Laboratory, Idaho

Strontium distribution coefficients (K{sub d}`s) were measured for 20 surficial sediment samples collected from selected sites at the Idaho national Engineering Laboratory (INEL). The measurements were made to help assess the variability of strontium K{sub d}`s found at the INEL as part of an ongoing investigation of strontium chemical transport properties of surficial and interbedded sediments at the INEL. The investigation is being conducted by the US Geological Survey and Idaho State University in cooperation with the US Department of Energy. Batch experimental techniques wee used to determine K{sub d}`s of surficial sediments using a synthesized aqueous solution representative of wastewater in waste disposal ponds at the INEL. Strontium K{sub d}`s of the 20 surficial sediments ranged from 36 {+-} 1 to 275 {+-} 6 milliliters per gram. These results indicate significant variability in the strontium sorptive capacities of surficial sediments at the INEL. Some of this variability can be attributed to physical and chemical properties of the sediment itself; however, the remainder of the variability may be due to compositional changes in the equilibrated solutions after being mixed with the sediment.