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George J Havrilla

Publications and source records attributed to George J Havrilla.

8 recordsLinked to original sources
PubMed2006

Detection of visible and latent fingerprints using micro-X-ray fluorescence elemental imaging.

Using micro-X-ray fluorescence (MXRF), a novel means of detecting fingerprints was examined in which the prints were imaged based on their elemental composition. MXRF is a nondestructive technique. Although this method requires a priori knowledge about the approximate location of a print, it offers a new and complementary means for detecting fingerprints that are also left pristine for further analysis (including potential DNA extraction) or archiving purposes. Sebaceous fingerprints and those made after perspiring were detected based on elements such as potassium and chlorine present in the print residue. Unique prints were also detected including those containing lotion, saliva, banana, or sunscreen. This proof-of-concept study demonstrates the potential for visualizing fingerprints by MXRF on surfaces that can be problematic using current methods.

Chlorine↗
PubMed2006

Integrating X-ray fluorescence and infrared imaging microspectroscopies for comprehensive characterization of an acetaminophen model pharmaceutical.

The integration of full spectral images using the complementary microspectroscopic imaging techniques X-ray fluorescence and Fourier transform infrared is demonstrated. This effort surpasses previous work in that a single chemometric software package is used to elicit chemical information from the integrated spectroscopic images. Integrating these two complementary spectroscopic methods provides both elemental and molecular spatial distribution within a specimen. The critical aspect in this work is using full spectral maps from each pixel within the image and subsequent processing with chemometric tools to provide integrated chemical information. This integration enables a powerful approach to more comprehensive materials characterization. Issues addressed include sample registration and beam penetration depth and how each affects post-processing. An inorganic salt and an acetaminophen pharmaceutical model mixture demonstrate the power of integrating these techniques with chemometric software.

Acetaminophen↗
PubMed2006

Elemental and molecular characterization of aged polydimethylsiloxane foams.

The application and integration of micro X-ray fluorescence (MXRF) and Fourier transform infrared (FT-IR) imaging to polydimethylsiloxane (PDMS) foam aging issues have been applied to cross-sectional images. Previous work has shown the tin in the stannous 2-ethylhexanoate catalyst to be highly mobile and it typically migrates to the PDMS foam upper surface. The current paper discusses a method for the integration of full spectral MXRF and FT-IR imaging of aged foams. Solvent extractions have also been performed on both fresh and aged foams to further examine aged foam properties. Combining elemental and molecular imaging techniques and applying them to PDMS aging provides synergistic information that aids in understanding the sample composition and distribution of components. Application of chemometric analysis to the full spectral elemental and molecular maps demonstrates correlations within the foams of the residual tin, organo-tin functional group moieties, and the presence of nitroplasticizer from an exogenous source.

Combinatorial Chemistry Techniques↗
PubMed2006

Attenuated total internal reflection infrared microspectroscopic imaging using a large-radius germanium internal reflection element and a linear array detector.

The number of techniques and instruments available for Fourier transform infrared (FT-IR) microspectroscopic imaging has grown significantly over the past few years. Attenuated total internal reflectance (ATR) FT-IR microspectroscopy reduces sample preparation time and has simplified the analysis of many difficult samples. FT-IR imaging has become a powerful analytical tool using either a focal plane array or a linear array detector, especially when coupled with a chemometric analysis package. The field of view of the ATR-IR microspectroscopic imaging area can be greatly increased from 300 x 300 microm to 2500 x 2500 microm using a larger internal reflection element of 12.5 mm radius instead of the typical 1.5 mm radius. This gives an area increase of 70x before aberrant effects become too great. Parameters evaluated include the change in penetration depth as a function of beam displacement, measurements of the active area, magnification factor, and change in spatial resolution over the imaging area. Drawbacks such as large file size will also be discussed. This technique has been successfully applied to the FT-IR imaging of polydimethylsiloxane foam cross-sections, latent human fingerprints, and a model inorganic mixture, which demonstrates the usefulness of the method for pharmaceuticals.

Dermatoglyphics↗
PubMed2003

Capillary electrophoresis micro X-ray fluorescence: a tool for benchtop elemental analysis.

A new tool was developed for separation and elemental detection by interfacing a simple capillary electrophoresis (CE) apparatus, constructed using a thin-walled fused-silica capillary, with a benchtop energy-dispersive micro X-ray fluorescence (MXRF) system. X-ray excitation and detection of the separated analytes was done using an EDAX Eagle II micro X-ray fluorescence system equipped with a polycapillary Rh target excitation source and a SiLi detector. It was demonstrated that this prototype system could be used for the separation and detection of species containing two different metals from one another, specifically Cu and Co. Free Co could also be separated from Co bound to cyanocobalamin (vitamin B-12). Two organic compounds were also separated from one another, a large biological protein, ferritin, from a small biological organic, cyanocobalamin. Preliminary average detection limits obtained on this system were on the order of 10(-)(4) M and compared favorably to those reported for the similar technique of CE-synchrotron XRF. CEMXRF allows for nondestructive, simultaneous, on-line, benchtop elemental analysis for chemical speciation applications.

Journal Article↗
PubMed2002

Development of microwave-assisted drying methods for sample preparation for dried spot micro-X-ray fluorescence analysis.

Although dried spot micro X-ray fluorescence (MXRF) is an effective analytical technique for trace elemental analysis, the sample preparation procedures currently used suffer from a number of drawbacks. These drawbacks include relatively long preparation times, lack of control of the sample preparation environment, and possibility of loss of volatile analytes during the drying process. Microwave-assisted drying offers several advantages for dried spot preparation, including control of the environment and minimized volatility because of the differences between microwave heating and conventional heating. A microwave-assisted drying technique has been evaluated for use in preparing dried spots for trace analysis. Two apparatus designs for microwave drying were constructed and tested using multielement standard solutions, a standard reference material, and a "real-world" semiconductor cleaning solution. Following microwave-assisted drying of these aqueous samples, the residues were redissolved and analyzed by ICPMS. Effective recovery was obtained using the microwave drying methods, demonstrating that the microwave drying apparatus and methods described here may be more efficient alternatives for dried spot sample preparation.

Journal Article↗
PubMedDate not supplied

Micro-X-ray fluorescence as a general high-throughput screening method for catalyst discovery and small molecule recognition.

A powerful high-throughput screening technique is described for the rapid screening of bead-based libraries for catalyst discovery and molecular recognition. Micro-X-ray fluorescence (MXRF) screens materials for elemental composition with mesoscale analysis. This method is nondestructive and requires minimal sample preparation and no special tags for analysis, and the screening time is dependent on the desired sensitivity. The speed, sensitivity, and simplicity of MXRF as a high-throughput screening technique were applied to screen bead-based libraries of oligopeptides for phosphate hydrolysis catalysts and molecular recognition of selective receptors for the degradation products and analogues of chemical warfare agents. This paper demonstrates the analytical or HTS capability of MXRF for combinatorial screening. It is meant only to show the capabilities of MXRF and is not meant as an exhaustive study of the catalyst and molecular recognition systems presented.

Catalysis↗