Student Abstracts: Chemistry at ORNL

Isotopic Analysis of Wire Mesh Samples Using Glow Discharge Mass Spectrometry. . GARY DOBBS (University of Central Arkansas, Conway, AR 72035) DOUGLAS C. DUCKWORTH (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
As part of the Nuclear Nonproliferation Treaty agreement, member state nuclear facilities are commonly surveyed for conformance. The usual sampling and analysis media include cloth and paper swipes. A new methodology employing wire mesh sampling and analysis is now being investigated. This concept is to provide effective surface sampling that can produce measurement samples compatible with a variety of radiological, elemental, and isotopic analytical techniques. The ideal method would produce sensitive, accurate, and precise analyses for each mesh sample in a timely and cost effective manner. Glow discharge mass spectrometry (GDMS) is a solid sampling elemental and isotope analytical technique that provides low parts per billion detection limits. To date, GDMS has given promising results in isotopic analysis for the wire mesh media. The purpose of this project is to extend and improve GDMS analysis of metal mesh and steel wool media. Typical analytical figures of merit will be reported. Once develo ped, this sampling medium and analytical methodology will result in more timely and cost efficient means of supporting nuclear safeguard activities.

Forensic Analysis Of Glass Using Inductively Coupled Plasma Mass Spectrometry. MEGHAN FINN (Virginia Tech, Blacksburg, VA 24060) DR. DOUGLAS DUCKWORTH (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Glass fragments are a common form of evidence in crimes such as burglary,vandalism, and hit and run accidents. Fragments can be recovered from a suspect's clothing and compared to the fragments from the crime scene. Historically refractive index (RI), an optical property, has been used to compare glass samples. Due to improvements in the glass manufacturing process and quality control measures, temporal variation in the refractive index has decreased, reducing the discriminatory power of RI. While the RI will continue as a mainstay in forensic glass analysis, the lack of discriminatory power has caused forensic scientists to investigate the use of trace elemental analysis. Inductively coupled plasma atomic emission spectrometry (ICP-AES) has been used successfully, and more recently inductively coupled plasma mass spectrometry (ICP-MS) has been investigated as a multielement technique that has lower detection limits than ICP-AES for many elements. A method has been developed using the ICP-MS to measure the concentration of 25Mg, 26Mg, 47Ti, 55Mn, 71Ga, 85Rb, 86Sr, 88Sr, 90Zr, 91Zr, 121Sb, 137Ba, 140Ce, 147Sm, 178Hf, and Pb, some of the most variant elements in glass. This method's variance has been measured within a single laboratory; however, before this method can be validated,the variance between laboratories must be determined. For this purpose, ORNL is participating in a round robin with the four other laboratories. Having this information should increase the judicial merit of glass evidence due to the fact that an accurate strength of association between unknown and known glass samples can be made with confidence.

In Search of the Elusive Quantum Dot: Using Microcantilevers as a Mask and in Detection Systems. SOPHIA MCCLAIN (Goerge Mason University, Fairfax, VA 22030) PANOS DATSKOS (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Nanostructures are currently being used in studies such as quantum electrical systems and biochemical assays. It is important to learn how to make and image the nanostructures used in these systems. To make the nanostructures holes are drilled into the tip of a microcantilever using a Focused Ion Mill. The microcantilevers are then used as a mask as gold is sputtered through the holes creating quantum dots and wires. These dots and wires are then imaged to prove that these structures can be fabricated by this method. Various forms of microscopy were experimented with to find the structures. A Multimode III Atomic Force Microscope and a Scanning Electron Microscope were used in the search for the quantum dots and wires.

Measurement of the pKa Values of pH Indicators in Solutions and Sol-Gel Matrix. KERRY-ANN MILLER (Miami-Dade Community College, miami, Fl. 33167) SHENG DAI (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Molecular imprinting is a synthesis technique developed to create specific binding sites for individual chemical compounds. Sol-gel based molecular imprinting has many advantages among which are its low temperature, transparency, and its ability to embed indicators into its matrix. By analyzing the absorbance of the indicator solution at different pHs using the UV-VIS spectrometer, it is possible to calculate the pKa shift to be used as a specific indicator. By entrapping the indicator into the matrix with various initial proton concentrations, the gel with various proton concentration will have a memory of the proton, which will cause the pKa shift of the entrapped indicators. Prior to the measurement of the sol-gel entrapped indicators, it is necessary to measure the pKa of the indicator in the solution. Spectra were taken of each indicator while the pH was adjusted . The pH of each spectrum was recorded for use later on in the experiment. A linear graph is constructed with the pH/ absorbance, and from this graph and using a formula that was composed of using a combination of Beer's Law and the Henderson Hasselbach equation, the pKa can be calculated. Results are pending due to calculation of data.

Xylose Metabolism Pathway of a Thermotolerant Yeast . ELISABETH PETIT-FOND (Miami-Dade community college, miami, fl 33167) JOHN NGHIEM (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Xylose metabolism of Kluyveromyces marxianus ATCC 36907, a thermotolerant yeast, was verified and studied under both aerobic and anaerobic conditions. The yeast was grown on LB medium supplemented with glucose and xylose. With initial xylose concentration of 5 g/L and glucose concentrations of 1,2,and 5 g/L, 55% of xylose was consumed over a period of 6 days under aerobic conditions. Under anaerobic conditions and over the same period, the percentage of xylose utilized increased from 6 to 18% as the glucose concentrations were increased from 1 to 5 g/L. The results indicated that the K. marxianus strain studied has a xylose metabolism pathway which can be enhanced by glucose.

Thermolysis of Substituted Benzyl Alcohols. JULIE PIGZA (Allegheny College, Meadville, PA 16335) DR. PHILLIP F. BRITT (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Lignin, the second most abundant biopolymer found in woody biomass, is an under-utilized resource of aromatic chemicals and fuel. However, the thermal degradation of lignin is poorly known. Previous pyrolysis studies on lignin model compounds, such as PhCH(OH)CH2OPh and PhCH(OH)CH(CH2OH)OPh, have found substituted benzyl alcohols as products but the degradation of these products is not known since both free radical and ionic reaction pathways are possible. The current work focuses on the reactivity of these substituted benzyl alcohols under pyrolysis conditions. Starting materials were first purified to >99.9% before pyrolysis. The pyrolysis reactions were carried out at 345°C for either thirty or ninety minutes. Specific features that were investigated were the influence of substituents on the reactivity. Scouting experiments have shown the reactivity of the molecules as follows: 4-hydroxybenzyl alcohol ~ 4-methoxy-alpha-methylbenzyl alcohol > 4-methoxybenzyl alcohol >> 3-hydroxybenzyl alcohol. The most likely decomposition mechanism contains both ionic and radical pathways, with ionic dominating, as determined by the products formed (identified by GC-FID and GC-MS). Establishing the reaction mechanisms of lignin model compounds can then provide insight into optimization of the pyrolysis process.

Proton Imprinting Via Sol-Gel Captivated pH Indicators. MICHAEL WEAVER (Pellissippi State Technical Community College, Knoxville, TN 37933) SHENG DAI (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
The various properties of sol-gel chemistry present many opportunities for nanoscale isolation and investigation. The encapsulation permitted by sol-gel chemistry has generated an interest in molecular imprinting. A fundamental experiment was conducted involving proton embedding in the sol-gel matrix. Several indicators, whose color varied with pH, were protonated (or deprotonated) in situ during sol-gel synthesis with acid (or base) catalysts. After the gel dried, with the indicator encapsulated, the gel was subjected to an analysis of visible light absorption as pH varied. An equation was derived from Beer's law and the Henderson-Hasselbach equation; this equation allowed straightforward determination of the equilibrium constant values for the proton gain or loss in the subject, embedded indicators. This analysis provided a direct comparison between established indicator equilibrium constant values in solution versus experimental sol-gel embedded indicator equilibrium constant values. Results indicate the sol-gel matrix confers protection to ionic species when free from extended aqueous storage, and subsequent chemical modification of the gel's surface with functional groups resulted in larger protection of the indicator. This experiment demonstrated the sol-gel's efficacy in surrounding and shielding charged ionic species on the molecular level.

High Precision Control System for an Acoustic Cavity Resonance Spectrometer. CARL WILLIS (Guilford College, Greensboro, NC 27410) DEBRA BOSTICK (Oak Ridge National Laboratory, Oak Ridge, TN 37831) .
Acoustic cavity resonance spectroscopy (ACRS) is a powerful new technique for measuring properties of fluid samples (critical points, for example) with unprecedented accuracy, precision, and rapidity. By tracking acoustic resonant frequencies in a sample-filled cavity, ACRS takes advantage of the sensitivity of the speed of sound to changes in the sample's density and elastic properties. The pressure, volume, and temperature of the sample must be precisely known when the acoustic measurements are taken, in order to realize the precision of which ACRS measurement is capable. Furthermore, temperature and volume should be user controllable so that measurements can be taken in a particular range of interest. We have developed a computerized volume and temperature control / measurement system, based on LabVIEW programming, for the ACRS housed at ORNL. A PID (proportional-integral-differential) algorithm drives the cavity oven for heating and a liquid nitrogen proportional valve for cooling. Sample temperature can be held constant or swept at a user-defined rate, with a deviation of less than 0.004 Celsius degrees, within the range of 20°C - 120°C. Resonator volume, adjustable between 0 and 8 mL by a stepper-motor-driven piston, is measured by a linear variable differential transformer (LVDT); volume changes are known to one microliter. Some challenges remain to be addressed in future work, primarily water condensation in electronics at low temperature, and inefficiency of the cooling mechanism. In further developments we expect to extend the lower temperature limit to -40°C. We also plan to verify the ACRS system's accuracy with CO2 critical point measurements.