Chemistry Unit

Quantico, VA, United States

Chemistry Unit

Quantico, VA, United States
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Mehltretter A.H.,Chemistry Unit | Wright D.M.,Chemistry Unit | Smith M.A.,Chemistry Unit
Forensic Chemistry | Year: 2017

Four commonly available duct tape products manufactured and sold in North America were analyzed both physically and chemically to determine if parameters such as scrim count, width, thickness (overall and backing/film), or adhesive composition vary for a single product manufactured over a span of several months. Chemical composition of the adhesive was determined using Fourier transform infrared spectroscopy (FTIR). In a previous study, these same products were analyzed to evaluate the intra-roll and intra-jumbo roll differences observed over the lengths and widths of duct tape rolls produced at single points in time, and minimal variation was noted in the recorded features. For this study, wider variation in some parameters was observed between jumbo rolls of the same product manufactured over time. While the means were found to differ in some limited instances, frequently the individual replicates/samples overlapped. Therefore, the intra-product population differences, even when statistically significant, were typically not considered a reliable basis for discrimination of individual samples. © 2017

Mehltretter A.H.,Chemistry Unit | Parish A.,Latent Prints Operations Unit
Science and Justice | Year: 2012

Forensic interest in adhesive tapes with polyvinyl chloride (PVC) backings (electrical tape) derives from their use in a variety of illicit activities. Due to the range of physical characteristics, chemical compositions, and homogeneity within a single roll of tape, traditional microscopic and chemical analyses can offer a high degree of discrimination between tapes, permitting the assessment of potential associations between evidentiary tape samples. The carbon isotope ratios of tapes could provide additional discrimination among tape samples. To evaluate whether carbon isotope ratios may be able to increase discrimination of electrical tapes, particularly with regards to different rolls of tape of the same product, we assessed the δ 13C values of backings from 87 rolls of PVC-based black electrical tape (~20 brands, >60 products) Prior to analysis, adhesives were removed to prevent contamination by adhering debris, and plasticizers were extracted because of concern over their potential mobility. This result is consistent with each of these tapes having approximately the same plasticizer δ 13C value and proportion of carbon in these plasticizers. The δ 13C values of the 87 PVC tape backings ranged between -23.5 and -41.3 (‰, V-PDB), with negligible carbon isotopic variation within single rolls of tape, yet large variations among tape brands and tape products. Within this tape population, carbon isotope ratios permitted an average exclusion power of 93.7%, using a window of +/-0.3‰; the combination of carbon isotope ratio measurement with additional chemical and physical analyses raises the discrimination power to over 98.9%, with only 41 out of a possible 3741 pairs of tape samples being indistinguishable. There was a linear relationship between the δ 13C value of tape backings and the change in δ 13C value with the extraction of plasticizers. Analyses of pre- and post-blast tape sample pairs show that carbon isotope signatures are within 0.3‰ of pre-blast values, indicating that carbon isotope values are largely preserved during an explosion. © 2011.

Olumayede E.G.,Chemistry Unit | Okuo J.M.,University of Benin
Polish Journal of Environmental Studies | Year: 2012

The living patterns of people may create different variations in concentrations of air pollutants in urban setting. Ambient VOCs measured in the Nigerian urban center of Benin City were analyzed and evaluated for variation characteristics; spatial, seasonal, and diurnal patterns of air pollutants. For this purpose samples were collected (from June 2009 to May 2010) at seven locations selected to represent local activities in the city. To determine the diurnal pattern of VOCs, four hourly samplings were carried out at six-day intervals. Samples were analyzed using gas chromatography. Among the VOC species detected are 4 alkanes, 6 aromatic compounds, 4 chlorinated hydrocarbons, and 1ketone. The results showed that ambient VOC levels in the atmosphere of Benin City are driven by high traffic; hence high concentrations were observed in most traffic junctions sampled. The examination of the average of total VOC accumulation showed significant spatial and easonal variability (p<0.01) in all sites. The diurnal pattern showed higher concentrations in the morning, and then evening, indicating that fresh emissions impact the air mass in the city. Analyses of the weekly variations of the pollutants showed the weekday's maxima and the weekend's minima, an indication of traffic influence.

Yaneva Z.L.,University of Chemical Technology and Metallurgy of Sofia | Yaneva Z.L.,Chemistry Unit | Koumanova B.K.,University of Chemical Technology and Metallurgy of Sofia | Allen S.J.,Queen's University of Belfast
Bulgarian Chemical Communications | Year: 2013

Nitrophenols represent one of the most challenging classes of pollutants requiring removal from wastewater streams due to their non-biodegradability and toxicity. The applicability of Rhizopus oryzae dead biomass as an alternative "eco-friendly" sorbent for 4-nitrophenol (4-NP) removal from aqueous phase was investigated in this study. The effect of initial sorbate concentration and adsorbent mass on the kinetics of adsorption were evaluated. The experimental kinetic results were analyzed by series of rate/mass transfer equations: pseudo-first, pseudo-second order model, Bangham's model, intra-particle diffusion model, and Elovich kinetic equation. Probably, 4-NP sorption on the dead biomass was mainly limited by chemisorption, but the role of intraparticle diffusion could not be neglected. The highest extend of 4-NP uptake determined in the recent study was 94 %. © 2013 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria.

Christensen A.M.,Laboratory Division | Smith M.A.,Chemistry Unit | Thomas R.M.,Laboratory Division
Journal of Forensic Sciences | Year: 2012

Forensic anthropological examinations typically involve the analysis of human skeletal remains, but in cases where samples are very small and/or physically compromised, it may first be necessary to determine whether the material is even osseous or dental in origin. X-ray fluorescence spectrometry (XRF) is a technique that reveals the elemental composition of materials and is hypothesized to have utility in such cases. XRF analysis was conducted on a variety of tissues and materials in unaltered and altered (damaged) states. With few exceptions, osseous and dental tissues in unaltered and altered conditions contained characteristic levels of calcium and phosphorus, while other materials did not. Materials could be accurately identified as osseous or dental in origin based on the calcium and phosphorus levels identified by XRF, and we therefore conclude that XRF analysis is a valid and effective means of determining osseous or dental origin of unknown material. © 2011 American Academy of Forensic Sciences.

Swider C.,Chemical Biological Radiological and Nuclear science Unit | Maguire K.,Chemical Biological Radiological and Nuclear science Unit | Rickenbach M.,Chemical Biological Radiological and Nuclear science Unit | Rickenbach M.,Chemistry Unit | And 5 more authors.
Journal of Forensic Sciences | Year: 2012

Following the September 11, 2001 terrorist attacks, letters containing Bacillus anthracis were distributed through the United States postal system killing five people. A complex forensic investigation commenced to identify the perpetrator of these mailings. A novel liquid chromatography/mass spectrometry protocol for the qualitative detection of trace levels of meglumine and diatrizoate in dried spore preparations of B. anthracis was developed. Meglumine and diatrizoate are components of radiographic imaging products that have been used to purify bacterial spores. Two separate chromatographic assays using multiple mass spectrometric analyses were developed for the detection of meglumine and diatrizoate. The assays achieved limits of detection for meglumine and diatrizoate of 1.00 and 10.0ng/mL, respectively. Bacillus cereus T strain spores were effectively used as a surrogate for B. anthracis spores during method development and validation. This protocol was successfully applied to limited evidentiary B. anthracis spore material, providing probative information to the investigators. 2012 American Academy of Forensic Sciences. Published 2012. This article is a U.S. Government work and is in the public domain in the U.S.A.

Faparusi F.,Biology Unit | Bello-Akinosho M.M.,Biology Unit | Oyede R.T.,Chemistry Unit | Adewole A.,Biology Unit | And 2 more authors.
Research Journal of Phytochemistry | Year: 2012

Brillantaisia patula is a medicinal plant used for different ailments in Africa. Phytochemical constituents and antibacterial potential of the plant were investigated. In vitro antibacterial activity using agar-well diffusion method was carried out against Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATGC 24212), Proteus hauseri (ATCG 13315), Pseudomonas aeruginosa ATCC 27853 and Escherichia coli (ATCC 38218). The phytochemistry of both methanol and ethanol extracts of Brillantaisia patula leaf revealed the presence of alkaloids, glycosides, terpenoids, steroids, flavonoids, tannins, steroids, flavonoids and saponins. Terpenoids and flavonoids were found in the methanolic extract but not in the ethanolic extract while steroid was found in the ethanolic extract but not in the methanolic extract. The ethanolic extract was active against all the five pathogenic bacteria while the methanolic extract inhibited all the test bacteria but Staphylococcus aureus. Ethanolic extract zones of inhibition ranged from 15.3±0.6 to 20.7±0.6 mm, whereas methanolic extract zones of inhibition ranged from 18.0±1.0 to 30.0±1.0 mm. The Minimum Inhibitory Concentration (MIC) of ethanolic extract ranged from 25 to 200 mg mL -1 while that of methanolic extract was from 50 to 100 mg mL -1. The Minimum Bactericidal Concentration (MBC) of methanolic extract ranged from 100 to 200 mg mL -1. The least MBC value (50 mg mL -1) of ethanolic extract was against Escherichia coli while the highest value (>200 mg mL -1) was against Proteus hauseri. Leaf of Brillantaisia patula could be a novel source of antibacterial agent (s) that might have broad spectrum activity. © 2012 Academic Journals Inc.

Morris-Kukoski C.L.,Chemistry Unit | Montgomery M.A.,Chemistry Unit | Hammer R.L.,Chemistry Unit
Journal of Analytical Toxicology | Year: 2014

Samples from a self-proclaimed cocaine (COC) user, from 19 drug users (postmortem) and from 27 drug chemists were extensively washed and analyzed for COC, benzoylecgonine, norcocaine (NC), cocaethylene (CE) and aryl hydroxycocaines by liquid chromatography- tandem mass spectrometry. Published wash criteria and cutoffs were applied to the results. Additionally, the data were used to formulate new reporting criteria and interpretation guidelines for forensic casework. Applying the wash and reporting criteria, hair that was externally contaminated with COC was distinguished from hair collected from individuals known to have consumed COC. In addition, CE, NC and hydroxycocaine metabolites were only present in COC users' hair and not in drug chemists' hair. When properly applied, the use of an extended wash, along with the reporting criteria defined here, will exclude false-positive results from environmental contact with COC.

Morris-Kukoski C.L.,Chemistry Unit | Schaff J.E.,Chemistry Unit | Reda L.J.,Chemistry Unit
Methods in Molecular Biology | Year: 2012

Solid-phase extraction and liquid chromatography-tandem mass spectrometry are invaluable techniques for the determination of benzodiazepines and metabolites in biological matrices. The reason for using tandem mass spectrometry is to increase limits of detection without the need for chemical derivatization. Here we describe a technique for the detection of 26 benzodiazepines and metabolites at a detection limit of approximately 1-2 ng/mL in blood and 1-5 ng/mL in urine when screened using a data-dependent scan method. © 2012 Springer Science+Business Media, LLC.

Bentley T.W.,Chemistry Unit | Koo I.S.,Korea National University of Education
Arkivoc | Year: 2012

Rate constants are reported at 25 °C for solvolyses of p-Z-substituted benzoyl chlorides (Z = O2N, Cl, H, Me, and MeO) in 2,2,2-trifluoroethanol (TFE) in binary mixtures with water or ethanol. Product selectivities (kTFE/kwater) are also reported. Previous work in which rate constants for solvolyses of benzoyl chlorides are correlated with σ constants is re-evaluated. V-shaped plots (assuming concurrent reactions) are constructed from logarithms of rate constants vs. σ (not σ ) for substituent effects or a suitable parameter for solvent effects. Conditions are established for which it is predicted that concurrent mechanisms (one dissociative, one associative) each contribute 50% towards the observed rate constants. © ARKAT-USA, Inc.

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