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1.
Goodpaster JV Sturdevant AB Andrews KL Brun-Conti L 《Journal of forensic sciences》2007,52(3):610-629
Comparisons of polyvinyl chloride electrical tape typically rely upon evaluating class characteristics such as physical dimensions, surface texture, and chemical composition. Given the various techniques that are available for this purpose, a comprehensive study has been undertaken to establish an optimal analytical scheme for electrical tape comparisons. Of equal importance is the development of a quantitative means for sample discrimination. In this study, 67 rolls of black electrical tape representing 34 different nominal brands were analyzed via scanning electron microscopy and energy dispersive spectroscopy. Differences in surface roughness, calendering marks, and filler particle size were readily apparent, including between some rolls of the same nominal brand. The relative amounts of magnesium, aluminum, silicon, sulfur, lead, chlorine, antimony, calcium, titanium, and zinc varied greatly between brands and, in some cases, could be linked to the year of manufacture. For the first time, quantitative differentiation of electrical tapes was achieved through multivariate statistical techniques, with 36 classes identified within the sample population. A single-blind study was also completed where questioned tape samples were correctly associated with known exemplars. Finally, two case studies are presented where tape recovered from an improvised explosive device is compared with tape recovered from a suspect. 相似文献
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Five marijuana samples were compared using bulk isotope analysis compound-specific isotope ratio analysis of the extracted cannabinoids. Owing to the age of our cannabis samples, four of the five samples were compared using the isotope ratios of cannabinol (CBN), a stable degradation product of Δ(9)-tetrahydrocannabinol (THC). Bulk δ(13)C isotope analysis discriminated between all five samples at the 95% confidence level. Compound-specific δ(13)C isotope analysis could not distinguish between one pair of the five samples at the 95% confidence level. All the measured cannabinoids showed significant depletion in (13)C relative to bulk isotope values; the isotope ratios for THC, CBN, and cannabidiol were on average 1.6‰, 1.7‰, and 2.2‰ more negative than the bulk values, respectively. A more detailed investigation needs to be conducted to assess the degree fractionation between the different cannabinoids, especially after aging. 相似文献
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John V. Goodpaster Ph.D. Amanda B. Sturdevant M.S. Kristen L. Andrews B.S. Eileen M. Briley M.S. Leanora Brun-Conti B.S. 《Journal of forensic sciences》2009,54(2):328-338
Abstract: The microtexture and elemental composition of the backing of electrical tapes have been shown to be highly discriminating. In this study, the organic composition of electrical tape was evaluated as a complementary means of distinguishing tape brands. The backing and adhesive of 72 rolls of electrical tape were analyzed via Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR) and discriminant analysis was used to classify all samples by brand. Generally, the accuracy for FTIR data (88–99%) was higher than that for elemental data (86–94%). FTIR spectra from the adhesive layer were the most discriminating. In separate studies, two fragments of blast-damaged tape were correctly assigned to their brand of origin and discriminant analysis was used to quantitatively associate or exclude tape samples from two bombing cases. 相似文献
4.
Case of Fatal Starvation: Can Stable Isotope Analysis Serve to Support Morphological Diagnosis and Approximate the Length of Starvation? 下载免费PDF全文
Marija Baković M.D. Ph.D. Polona Vreča Ph.D. Davor Mayer M.D. Ph.D. 《Journal of forensic sciences》2017,62(1):258-264
The diagnosis of death as a result of starvation is established on anthropological measurements, visual appearance of the deceased on external and internal examination, microscopic analysis, laboratory testing, and exclusion of other causes of death. Herein, we present our findings on a case of 95‐year‐old man who died of starvation. After the diagnosis of starvation was established by traditional forensic medicine methods, we have conducted retrospective segmental analysis of stable carbon (δ13C) and nitrogen (δ15N) isotope ratios in hair sample. This method reveals periods of starvation through decrease in δ13C and increase in δ15N along the strand of hair. Our analysis revealed the decrease of 0.6 ‰ in δ13C during the last 10–12 weeks prior to death, similar as reported in other investigations. Also, a decrease of 0.7 ‰ in δ15N during the last 8–10 weeks prior to death was determined that was different than observed in previous studies. 相似文献
5.
The backings of 90 black electrical tapes were analyzed to evaluate the chemical components of these films, the ability of individual techniques to discriminate samples, and the ability of the techniques combined to distinguish samples. The techniques utilized and their respective discrimination results were stereomicroscopy and physical measurements, to include observation of surface features of the backing, width, and thickness measurements (c. 64%); Fourier transform infrared spectroscopy (FTIR) using a microscope accessory (c. 83%); pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS; c. 81%); and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS; c. 87%). Ninety-four percent of the backings were discriminated through this combination of analytical methods. Finally, evaluating these results in conjunction with previously published data on the analysis of the adhesives from the same set of electrical tapes provided an overall discrimination of nearly 96%. 相似文献
6.
Cyanide is one of the common poisons in murders. When cyanide has been used, to identify the origin of cyanide may be necessary in the forensic investigation. We have examined the possibility of distinguishing different commercial cyanide samples through the δ(13)C and δ(15)N values and developed a protocol for the isotope analysis of cyanide extracted from several matrices as food and medicine. Several cyanide precipitates were tested for the isotope analysis. The results show that cupric ferrocyanide Cu(2)[Fe(CN)(6)] is the most appropriate precipitate for the analysis. Thirteen batches of KCN and nine batches of NaCN chemicals were randomly chosen from different suppliers. The cyanides were converted to cupric ferrocyanide and then analysed by isotope ratio mass spectrometry coupled to elemental analysis (EA-IRMS). The isotopic signature of the commercial samples varied from -51.96 to -25.77 ‰ for δ(13)C and from -4.51 to +3.81 ‰ for δ(15)N, highlighting the potential of applying EA-IRMS technique to identify cyanide from different batches and sources. The influence of the cyanide extraction and isolation from spiked matrix on the isotopic analysis was also studied. Three matrices: orange juice, yogurt drink and a medicine were tested. In many cases, the isotopic analysis results obtained from the original cyanides precipitates and those isolated from the matrices showed a good accordance, especially for δ(15)N. In some matrices, the (13)C analysis was interfered by co-precipitates. With carefully elaborated working protocol, determining the isotope ratio of N and C in cyanide by EA-IRMS is a promising method for forensic investigations. 相似文献
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Hiroto Kawashima Ph.D. 《Journal of forensic sciences》2015,60(5):1360-1364
Between December 2007 and January 2008, people suffered from food poisoning in the Japanese prefectures of Chiba and Hyogo after eating frozen dumplings (gyoza) produced in China, which had very high concentrations (1490–19,290 ppm) of methamidophos (O,S‐dimethyl phosphoramidothioate). Thus, we measured the stable carbon isotope ratio of methamidophos using GC/C/IRMS to identify the source. We analyzed seven methamidophos reagents and one Chinese agricultural methamidophos chemical (MTD600) that contained many impurities. The δ13C values of the seven methamidophos reagents and MTD600 ranged from ?49.23‰ to ?31.90‰, with an average SD of 0.20‰, very high precision. This difference (17.33‰) was very large compared with that in previous reports and may be attributable to the material itself and the chemical processing of methamidophos. Criminals can easily obtain pesticides such as methamidophos; therefore, it is very important to identify the pesticide source and distribution route using stable isotopic science in the future. 相似文献
10.
In this study, δ13C values of six cocaine samples were identified and classified using a single quadrupole mass spectrometer and an isotope ratio mass spectrometry (IRMS) as simultaneous gas chromatography detectors. Our instrument modification is simple to use and is useful (i) when the sample is of limited size or can only be injected once, (ii) to help identify peaks in a complicated IRMS chromatogram, and (iii) to help differentiate very simple systems when impurity profiling is not possible. The EI-MS confirmed the identity of cocaine in each sample. The IRMS data distinguished 12 of the 15 possible pair-wise comparisons at the 95% CL. Three samples could not be differentiated by their δ13C ratios for cocaine. ANOVA demonstrated that the measurement variance was consistently larger than the sample variance. As the δ13C values clearly show, this technique enables the exclusion of a potential common source even when two samples have otherwise identical chemical and physical properties. 相似文献
11.
Because there are no internationally distributed stable hydrogen and oxygen isotopic reference materials of human hair, the U.S. Geological Survey (USGS) has prepared two such materials, USGS42 and USGS43. These reference materials span values commonly encountered in human hair stable isotope analysis and are isotopically homogeneous at sample sizes larger than 0.2 mg. USGS42 and USGS43 human-hair isotopic reference materials are intended for calibration of δ(2)H and δ(18)O measurements of unknown human hair by quantifying (1) drift with time, (2) mass-dependent isotopic fractionation, and (3) isotope-ratio-scale contraction. While they are intended for measurements of the stable isotopes of hydrogen and oxygen, they also are suitable for measurements of the stable isotopes of carbon, nitrogen, and sulfur in human and mammalian hair. Preliminary isotopic compositions of the non-exchangeable fractions of these materials are USGS42(Tibetan hair)δ(2)H(VSMOW-SLAP) = -78.5 ± 2.3‰ (n = 62) and δ(18)O(VSMOW-SLAP) = +8.56 ± 0.10‰ (n = 18) USGS42(Indian hair)δ(2)H(VSMOW-SLAP) = -50.3 ± 2.8‰ (n = 64) and δ(18)O(VSMOW-SLAP) = +14.11 ± 0.10‰ (n = 18). Using recommended analytical protocols presented herein for δ(2)H(VSMOW-SLAP) and δ(18)O(VSMOW-SLAP) measurements, the least squares fit regression of 11 human hair reference materials is δ(2)H(VSMOW-SLAP) = 6.085δ(2)O(VSMOW-SLAP) - 136.0‰ with an R-square value of 0.95. The δ(2)H difference between the calibrated results of human hair in this investigation and a commonly accepted human-hair relationship is a remarkable 34‰. It is critical that readers pay attention to the δ(2)H(VSMOW-SLAP) and δ(18)O(VSMOW-SLAP) of isotopic reference materials in publications, and they need to adjust the δ(2)H(VSMOW-SLAP) and δ(18)O(VSMOW-SLAP) measurement results of human hair in previous publications, as needed, to ensure all results on are on the same scales. 相似文献
12.
Aziz N Greenwood PF Grice K John Watling R van Bronswijk W 《Journal of forensic sciences》2008,53(5):1130-1137
Pressure-sensitive adhesive tapes often represent key evidence of crimes such as assault, rape or homicide; thus, the development of analytical techniques able to contribute to a detailed characterization of these materials is of forensic importance. The gas chromatography-mass spectrometry (GCMS) analysis of the solvent extractable fractions of a suite of electrical and gaffer adhesive tapes spanning a range of colors and manufacturers identified a number of petroleum-derived hydrocarbons. Molecular and isotopic analyses of hydrocarbon constituents of complex materials have found wide analytical utility including the forensic investigation of oil spills and arson. Here, we investigate the utility of these techniques for characterizing the hydrocarbon composition of pressure-sensitive adhesive tapes for forensic correlation purposes. Subtle distinction of tape samples was evident in the GCMS distribution of several hydrocarbon groups including alkyl-naphthalenes, hopane and sterane biomarkers. Linear discriminant analysis of the abundances of these products provided high level differentiation of tape manufacturer. The distinction of different adhesive tape samples was further extended by measurement of their stable carbon isotopic values. The molecular and isotopic differences of the petroleum content of tapes are consistent with the use of different petroleum materials used in the manufacturing process and demonstrate the benefits of the combined use of complementary oil hydrocarbon characterization approaches. This study reveals the forensic potential of using established petroleum characterization methods for characterizing materials with a petroleum-derived hydrocarbon element. 相似文献
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The forensic application of stable isotope analysis to cocaine and heroin for geolocation of exhibits must take into account the possible enrichment and/or depletion of 13C and 15N during the illicit manufacturing process. Continuous-flow elemental analysis-isotope ratio mass spectrometry was utilized to measure changes in the stable isotope ratios of carbon and nitrogen for both cocaine (N = 92) and heroin/morphine (N = 81) exhibits derived from illicit manufacturing processes utilized by South American clandestine chemists. In controlled settings in South America, there was no siginficiant carbon isotope fractionation during the conversion of cocaine base to cocaine HCI using current illict methodologies. In contrast, nitrogen isotope fractionation for this conversion was 1 per thousand. There was a kinetic carbon isotope ratio fractionation during the acetylation of Colombian morphine to heroin and as a result heroin exhibits will almost always have more negative delta13C values than the original morphine. There was an isotopic fractionation against 15N during the acetylation of morphine base to heroin base, but this effect was not expressed since all of the heroin base was precipitated during the manufacturing process. However, the clandestine process of converting a single batch of heroin base usually involved two consecutive crops of heroin HCl and the latter crop was isotopically depleted as expected from a Rayleigh distillation process. When heroin was deacetylated to morphine, the morphine produced resulted in delta13C values that were indistinguishable from the original morphine. The kinetic carbon isotope fractionation factor for the South American process of morphine acetylation was -1.8 per thousand, allowing calculation of the delta13C values of the acetic anhydride from deacetylated heroin delta13C values. 相似文献
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Plastics including adhesive tapes, cable ties, and packaging are common evidence types encountered in forensic investigations and casework. Traditional examination techniques such as Fourier Transform Infrared (FTIR) spectroscopy lack specificity and are unable to discern differences within the same polymer structures leaving the analyst with a generic identification. High quality manufacturing methods further amplify the limitations in detecting variability between samples. Isotope Ratio Mass Spectrometry (IRMS) has been shown to be a valuable technique in further discriminating plastics. Discrimination is achieved by analysing the relative abundances of stable isotopes within a sample, with differences detected in isotope ratios possibly attributed to the source of raw materials and fractionation during the manufacturing process. A survey of cling wraps and re-sealable zipper storage bags collected in the Australian Capital Territory was undertaken to assess the variability in carbon and hydrogen isotope ratios of different brands and samples. The results of this research are discussed, particularly with respect to within and between brand trends, and a case study is presented as an example of the value of including IRMS in a casework context. 相似文献
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Carbon and Nitrogen Stable Isotope Analyses of Ephedra Plant and Ephedrine Samples and Their Application For Methamphetamine Profiling 下载免费PDF全文
Cuimei Liu Ph.D. Peipei Liu M.S. Wei Jia M.S. Yingfeng Fan M.S. 《Journal of forensic sciences》2018,63(4):1053-1058
In this study, stable isotope ratio analysis was used to track the precursor information of methamphetamine. The δ13C and δ15N values of 30 nature ephedra plants, 12 synthetic ephedrine/pseudoephedrine (ephedrine), 14 natural ephedrine, and 987 seized methamphetamine samples were measured and compared. Due to different weather and earth conditions, the δ13C and δ15N values of ephedra plants grown in the east and the west of Inner Mongolia showed great difference. The δ15N values of ephedra plants were consistent with related ephedrine extracted from them. Moreover, the criteria to infer the synthetic origin of ephedrine were set up after the analysis of natural and synthetic ephedrine samples. Finally, the precursor origins of 949 seized methamphetamine samples synthesized by Emde and Nagai method were tentatively inferred. Influenced by different preprecursors, the δ13C values of seized methamphetamine samples that synthesized from P2P also showed great difference, and this result is consistent with the reported data. 相似文献
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目的探索电工胶带带基的元素检验方法。方法利用扫描电镜/能谱法(SEM/EDS)对电工胶带带基中的主体元素进行定量分析,通过SPSS软件对SEM/EDS定量分析法检测出的主体元素(Cl和Ca)相对含量进行统计分析;利用X射线荧光光谱法(XRF)对电工胶带带基中的微量元素进行定性分析。结果34个品牌红色电工胶带组成的561组样品对通过SEM/EDS定量分析法可以区分539组,区分率达到96.1%;根据XRF法定性分析测出的Mg、Al、Si、S、Ti、Sb、Ba、Pb微量元素的不同组合可将34种电工胶带分成11组,两种方法结合可使不同品牌红色电工胶带的区分率达到98.4%。结论SEM/EDS法和XRF法结合可以实现同种颜色、不同品牌电工胶带的高效区分。 相似文献
18.
《Science & justice》2014,54(5):327-334
This paper considers how likelihood ratios can be derived for a combination of physical, chemical and isotopic measurements. Likelihood ratios were formulated based on the characteristics of a small convenience sample of 20 duct tapes. The propositions considered were:
- Hptwo samples are from the same batch
- Hdtwo samples are from different batches.
19.
Attenuated total reflection (ATR), also known as internal reflection spectroscopy (IRS), is a forensically accepted method for infrared (IR) analysis of pressure sensitive adhesive tapes. Advancements of ATR accessories in the last decade have provided the forensic examiner several ATR methods to choose from. These accessories offer a variety of ATR crystal choices with a variety of prices and capabilities. Four different types of pressure sensitive adhesive tapes including duct tape, electrical tape, packaging tape and office tape have been used to compare six different ATR methods. Each of the methods tested offers both benefits and limitaltions which must be considered for the type of sample to be analyze. The intent of this paper is to assist the reader in better understanding ATR techniques, the many differences among currently available ATR accessories and how the method is applied to the analysis of pressure sensitive adhesive tape. 相似文献
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Assessing Carbon and Hydrogen Isotopic Fractionation of Diesel Fuel n-alkanes During Progressive Evaporation 下载免费PDF全文
Syahidah A. Muhammad Ph.D. Alan R. Hayman Ph.D. Robert Van Hale Ph.D. Russell D. Frew Ph.D. 《Journal of forensic sciences》2015,60(Z1):S56-S65
Compound-specific isotope analysis offers potential for fingerprinting of diesel fuels, however, possible confounding effects of isotopic fractionation due to evaporation need to be assessed. This study measured the fractionation of the stable carbon and hydrogen isotopes in n-alkane compounds in neat diesel fuel during evaporation. Isotope ratios were measured using a continuous flow gas chromatograph/isotope ratio mass spectrometer. Diesel samples were progressively evaporated at 24 ± 2°C for 21 days. Increasing depletion of deuterium in nC12–nC17 alkanes in the remaining liquid with increasing carbon chain length was observed. Negligible carbon isotope fractionation was observed. Preferential vaporization was measured for the shorter chain n-alkanes and the trend decreased with increasing chain length. The decrease in δ2H values indicates the preferential vaporization of the isotopically heavier species consistent with available quantitative data for hydrocarbons. These results are most important in the application of stable isotope technology to forensic analysis of diesel. 相似文献