The forensic characterization of polyethylene films by elemental analysis using total-reflection X-ray fluorescence (TXRF) spectrometry.
Item
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Title
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The forensic characterization of polyethylene films by elemental analysis using total-reflection X-ray fluorescence (TXRF) spectrometry.
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Identifier
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AAI9924798
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identifier
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9924798
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Creator
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Buscaglia, JoAnn.
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Contributor
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Adviser: Peter R. De Forest
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Date
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1999
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Analytical | Sociology, Criminology and Penology
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Abstract
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Plastic trash bags are encountered as physical evidentiary materials in the investigation and adjudication of homicides, narcotics trafficking, and dumping of hazardous waste. Currently, forensic examinations of plastic bags consist of comparisons of physical patterns arising from random processes during manufacture. The discrimination capability of this approach is limited by sample size, opacity, thermal or mechanical distortion of the bag, and the need for consecutively or nearly consecutively manufactured bags for comparison. Conversely, the inorganic elemental composition of a polymeric material is stable, even after thermal or physical alteration, or exposure to harsh environmental conditions. Further, there should be limited variation in elemental concentrations during a production run. Differences in elemental profiles among plastic bags are expected, because a variety of inorganic constituents are introduced intentionally and accidentally into plastic bags during the manufacturing process.;In this study, the concentrations of selected elements in commercially available polyethylene trash bags were determined using total-reflection X-ray fluorescence (TXRF) spectrometry. Samples of polyethylene bags were cut, cleaned, and weighed, followed by removal of the polymer matrix by oxygen plasma ashing. The ash residue was quantitatively transferred to the TXRF quartz sample support and an internal standard was added. Removal of the polymer matrix yielded better detection limits for all elements of interest than a solid sample preparation method.;Replicate samples from individual bags from three manufacturers were analyzed in order to determine the variability in element concentrations within each bag. The compositional variation was also determined within and among individual bags, boxes, production lots, and manufacturers. Of the 18 elements readily determinable in most specimens, titanium (Ti), iron (Fe), zinc (Zn), calcium (Ca), strontium (Sr) and barium (Ba) are the most useful for discrimination among manufacturing sources. These element concentrations vary greatly among manufacturers and production runs, but are consistent within individual bags and among bags from a single box. Results of this research indicate that bags produced from the same manufacturer and product line in different plants, and at different times in the same plant, are analytically distinguishable.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
