George L. Donati
B.S. 2000, University of the Guaxupé Educational Foundation (Brazil)
M.Sc. 2006, Federal University of São Carlos (Brazil, Prof. Joaquim A. Nóbrega)
Ph.D. 2010, Wake Forest University (Prof. Bradley T. Jones)
Postdoctoral Research Associate 2010-2012, Federal University of São Carlos (Brazil, Prof. Joaquim A. Nóbrega)
Teacher-Scholar Postdoctoral Fellow 2012-2013, Wake Forest University
Office: Salem 116A
Phone: (336) 758-4815
Home Page: https://sites.google.com/site/georgedonati7
Analytical Chemistry Instrumentation for Trace Element Analysis
Trace elements play a critical role in many processes and the demand for the determination of their chemical forms and concentrations in samples of economic, technological and environmental importance have steadily increased in the last few decades. The significance of such analytes can be observed by the different pieces of legislation establishing their maximum levels in several samples, and their role in the development of new drugs, materials, and processes.
In the Donati lab we develop analytical methods to determine trace levels of metals and nonmetals in many different samples; from biodiesel fuel, to superficial waters, plant material, and animal tissue. Our research is focused on designing, constructing and evaluating the analytical performance of low-cost, portable instrumentation for trace element analysis. We also develop new strategies to improve the performance of commercial instruments such as inductively coupled plasma with optical emission (ICP OES) or mass spectrometry (ICP-MS) detections.
Applying ICP-MS for the Early Diagnosis of Osteoporosis
The determination of chemical imbalances typically present at the onset of some aggressive diseases may be used for early diagnosis, which could reduce mortality and contribute for more efficient treatments. An interesting approach for nutritional and toxicological studies is the determination of minerals in fingernails and toenails. The concentrations of certain elements in these samples can be significantly different in healthy or sick individuals, and some works have demonstrated the efficiency of using nails as biological markers. More often than not, these elemental concentration changes are very subtle, especially at the onset of diseases. Therefore, a sensitive method is required to detect such small changes and contribute to diseases diagnostics. In this project, we take advantage of ICP-MS’ high sensitivity to identify subtle changes in the body’s mineral balance caused by osteoporosis. In collaboration with Profs. Thomas Smith and Cynthia Emory with the Wake Forest Medical School, and Dr. Keith Levine with the Research Triangle Institute we determine and compare the levels of different elements in fingernails and toenails of healthy individuals and patients with osteoporosis. We look to determining elemental signatures that could represent a less expensive, noninvasive method to identify at-risk individuals during the initial phases of osteoporosis.
Evaluating the Efficiency of Gallium as an Antimicrobial Agent
Studies have shown that Ga compounds can be effective at eliminating microorganisms responsible for several different diseases; from syphilis to tuberculosis, malaria and even multiple drug-resistant varieties of bacteria. However, very little is known about the mechanisms involved in gallium’s antimicrobial activity. One hypothesis is based on gallium’s ability to enter microbes’ cells through their iron transport mechanisms. Then, it can disrupt Fe metabolism, and interfere with DNA and protein synthesis. The solution and coordination chemistries of Ga3+ and Fe3+ are very similar, which can be attributed to comparable ionic radii and ionic/covalent characteristics while forming bonds. On the other hand, microorganisms are usually “hungry” for Fe to be used in processes closely related to their growth. Therefore, microorganisms are tricked into absorbing Ga as if it were Fe, which ultimately results in their demise.
In this project, we evaluate the minimal concentrations of Ga necessary to eliminate bacteria. In collaboration with Prof. Patrica dos Santos, we use B. subtilis as a gram-positive bacteria model that may be applied to other more infectious varieties of microorganisms. We use ICP OES to determine Ga concentrations absorbed by the microorganisms, which will eventually help us better understand the mechanisms involved in Ga efficiency as an antimicrobial agent.
Laser Pointer Tungsten Coil Atomic Fluorescence Spectrometry for Trace Metal Analysis
In this project we use a simple blue laser pointer as radiation source to promote atomic fluorescence and eventually determine trace level concentrations of metals in different samples. The idea is to build a low cost, portable instrument powered by a small battery and based on a tungsten coil atomizer extracted from commercially available microscope light bulbs. The handheld system may then be easily transported to the field for in situ analyses.
Improving Accuracy in ICP-MS Determinations by the Interference Standard Method
Inductively coupled plasma mass spectrometry (ICP-MS) has become one of the most useful tools in modern analytical chemistry. Because of a single combination of high sensitivity and multi-element capabilities, this method has been successfully used in the most diverse fields. Despite all this success, a critical limitation prevents ICP-MS from reaching its full potential. Since it was proposed as a sensitive method for trace element determinations, problems related to spectral interferences have hindered ICP-MS’ application to complex matrices. Most instruments are based on quadrupole mass analyzers (ICP-QMS), which are less expensive, but present a relatively low resolution. Thus, severe interferences caused by spectral overlap either from concomitant isotopes or polyatomic ions make it difficult the application of ICP-QMS to some elements.
A new approach to minimizing spectral interferences in ICP-QMS determinations has recently been proposed by our group in collaboration with Prof. Joaquim Nóbrega of the Federal University of São Carlos, in Brazil. The interference standard (IFS) method is based on the hypothesis that interfering polyatomic ions and plasma naturally occurring species (IFS) present similar behaviors in the plasma. Thus, by dividing the analytical signal (analyte plus interfering ion) by the IFS signal, one can minimize the contribution of the interfering species to the overall analytical signal and improve ICP-QMS accuracy. The IFS method was applied to different samples and it has been shown effective even for some severely affected analytes such as 28Si+ and 32S+. It is simple and inexpensive since no instrumental modification or introduction of gases into the system are required.
In this project, we evaluate new IFS species to improve ICP-MS accuracy in applications dealing with different complex matrices. We also seek to better understand the mechanisms responsible for the IFS method efficiency.