Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 40
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Anal Chem ; 91(16): 10622-10630, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31322860

RESUMO

Fingermarks are an important form of crime-scene trace evidence; however, their usefulness may be hampered by a variation in response or a lack of robustness in detection methods. Understanding the chemical composition and distribution within fingermarks may help explain variation in latent fingermark detection with existing methods and identify new strategies to increase detection capabilities. The majority of research in the literature describes investigation of organic components of fingermark residue, leaving the elemental distribution less well understood. The relative scarcity of information regarding the elemental distribution within fingermarks is in part due to previous unavailability of direct, micron resolution elemental mapping techniques. This capability is now provided at third generation synchrotron light sources, where X-ray fluorescence microscopy (XFM) provides micron or submicron spatial resolution and direct detection with sub-µM detection limits. XFM has been applied in this study to reveal the distribution of inorganic components within fingermark residue, including endogenous trace metals (Fe, Cu, Zn), diffusible ions (Cl-, K+, Ca2+), and exogeneous metals (Ni, Ti, Bi). This study incorporated a multimodal approach using XFM and infrared microspectroscopy analyses to demonstrate colocalization of endogenous metals within the hydrophilic organic components of fingermark residue. Additional experiments were then undertaken to investigate how sources of exogenous metals (e.g., coins and cosmetics) may be transferred to, and distributed within, latent fingermarks. Lastly, this study reports a preliminary assessment of how environmental factors such as exposure to aqueous environments may affect elemental distribution within fingermarks. Taken together, the results of this study advance our current understanding of fingermark composition and its spatial distribution of chemical components and may help explain detection variation observed during detection of fingermarks using standard forensic protocols.

2.
Forensic Sci Int ; 298: 88-96, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30884439

RESUMO

Lipstick traces may be encountered in forensic investigations as traces left on clothing, drinkware, tissue papers or other surfaces. However, their probative value is limited by the discriminatory power and destructiveness of existing analysis schemes. This work employed analytical spectroscopy with chemometrics to provide objective and non-destructive characterisation of lipsticks for forensic purposes. 22 red-shaded and 18 nude-shaded lipsticks were analysed using visible absorbance and diffuse reflectance spectroscopy, as well as attenuated total reflectance Fourier transform infrared spectroscopy. Principal component analysis readily distinguished most samples based on their spectral profiles, with subsequent models yielding discrimination accuracies exceeding 94% for each spectroscopic mode. This could provide a greater level of confidence when conducting 'questioned versus known' comparisons of similar lipsticks. Further testing using external validation sets produced identification accuracies of 73-100 %, which may allow investigative leads to be more readily obtained from recovered lipstick traces.

3.
Analyst ; 143(17): 4027-4039, 2018 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-29956693

RESUMO

Latent fingermarks are an important form of crime-scene trace evidence and their usefulness may be increased by a greater understanding of the effect of chemical distribution within fingermarks on the sensitivity and robustness of fingermark detection methods. Specifically, the relative abundance and micro-distribution of sebaceous (lipophilic) and eccrine (hydrophilic) material in fingermarks have long been debated in the field, yet direct visualisation of relative abundance and micro-distribution was rarely achieved. Such a visualisation is nonetheless essential to provide explanations for the variation in reproducibility or robustness of latent fingermark detection with existing methods, and to identify new strategies to increase detection capabilities. In this investigation, we have used SR-ATR-FTIR and confocal Raman microscopy to probe the spatial micro-distribution of the sebaceous and eccrine chemical components within latent fingermarks, deposited on non-porous surfaces. It was determined that fingermarks exhibit a complex spatial distribution, influenced by the ratio of lipophilic to aqueous components, and to a first approximation resemble a water-in-oil or oil-in-water emulsion. Detection of a substantial lipid component in "eccrine enriched fingermarks" (wherein hands are washed to remove lipids) is noteworthy, as it provides a potential explanation for several scenarios of unexpected fingermark detection using methods previously thought unsuitable for "eccrine deposits". Furthermore, the pronounced distribution of lipids observed in natural fingermark deposits was intriguing and agrees with recent discussion in this research field that natural fingermarks contain a much higher lipid content than previously thought.

4.
PLoS One ; 12(12): e0189177, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29281650

RESUMO

Explosives are a common soil contaminant at a range of sites, including explosives manufacturing plants and areas associated with landmine detonations. As many explosives are toxic and may cause adverse environmental effects, a large body of research has targeted the remediation of explosives residues in soil. Studies in this area have largely involved spiking 'pristine' soils using explosives solutions. Here we investigate the fate of explosives present in soils following an actual detonation process and compare this to the fate of explosives spiked into 'pristine' undetonated soils. We also assess the effects of the detonations on the physical properties of the soils. Our scanning electron microscopy analyses reveal that detonations result in newly-fractured planes within the soil aggregates, and novel micro Computed Tomography analyses of the soils reveal, for the first time, the effect of the detonations on the internal architecture of the soils. We demonstrate that detonations cause an increase in soil porosity, and this correlates to an increased rate of TNT transformation and loss within the detonated soils, compared to spiked pristine soils. We propose that this increased TNT transformation is due to an increased bioavailability of the TNT within the now more porous post-detonation soils, making the TNT more easily accessible by soil-borne bacteria for potential biodegradation. This new discovery potentially exposes novel remediation methods for explosive contaminated soils where actual detonation of the soil significantly promotes subsequent TNT degradation. This work also suggests previously unexplored ramifications associated with high energy soil disruption.


Assuntos
Substâncias Explosivas , Poluentes do Solo/análise , Trinitrotolueno/química , Bactérias/metabolismo , Disponibilidade Biológica , Microscopia Eletrônica de Varredura , Porosidade , Microbiologia do Solo , Trinitrotolueno/análise , Trinitrotolueno/metabolismo , Microtomografia por Raio-X
5.
Anal Chem ; 89(8): 4729-4736, 2017 04 18.
Artigo em Inglês | MEDLINE | ID: mdl-28337908

RESUMO

A new electrochemical method to detect and quantify the explosive compound 2,4,6-trinitrotoluene (TNT) in aqueous solutions is demonstrated. A disposable thin-film electrode modified with a droplet of a gel-polymer electrolyte (GPE) was immersed directly into samples of TNT at concentrations of 1-10 µg/mL. The GPE contained the hydrophobic room-temperature ionic liquid (RTIL) trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([P14,6,6,6][NTf2]) and the polymer poly(hexyl methacrylate). The RTIL acted to preconcentrate TNT into the GPE and provided ionic conductivity. The polymer provided both (i) sufficient viscosity to ensure mechanical stability of the GPE and (ii) strong hydrophobicity to minimize leaching of the RTIL. Square wave voltammetry was performed on the first reduction peak of TNT-preconcentrated samples (15 min soaking with mechanical stirring), with linear plots of peak current vs cumulative concentration of TNT, giving an averaged limit of detection of 0.37 µg/mL (aqueous phase concentration). Additionally, the voltammetry of the first reduction peak of TNT in [P14,6,6,6][NTf2] was unaffected by the presence of oxygen-in contrast to that observed in an imidazolium-based RTIL-providing excellent selectivity over oxygen in real environments. The sensor device was able to quickly and easily quantify TNT concentrations at typical ground water contamination levels. The low-cost and portability of the sensor device, along with the minimal amounts of GPE materials required, make this a viable platform for the onsite monitoring of explosives, which is currently a significant operational challenge.

6.
Forensic Sci Int ; 268: 62-72, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27693827

RESUMO

Single metal deposition (SMD II), a recently proposed method for the development of latent fingermarks, was investigated by systematically altering aspects of the procedure to assess their effect on the level of development and contrast achieved. Gold nanoparticle size, temperature of the deposition solution bath, and orbital shaking during detection were shown to affect the levels of development and contrast obtained. Gold nanoparticles of diameter 15-21nm were found to be most effective for satisfactory visualisation of latent fingermarks, while solutions that were applied at room temperature were found to adequately balance the ratio between the contrast of the fingermark ridge detail and the level of background staining achieved. Finally, optimum levels of development and contrast were obtained through constant agitation of both solution baths at approximately 50RPM throughout the submersion time. SMD II was also tested on a large variety of substrate types and shown to be effective on a range of porous, non-porous, and semi-porous surfaces; however, the detection quality can be significantly influenced by the substrate nature. This resulted in the production of dark grey, white, or gold coloured fingermarks on different surfaces, as well as reversed detection on certain types of plastic, similarly seen through the use of vacuum metal deposition.


Assuntos
Dermatoglifia , Ouro , Nanopartículas Metálicas , Adulto , Feminino , Medicina Legal/métodos , Humanos , Masculino , Análise Espectral , Propriedades de Superfície , Vácuo , Adulto Jovem
7.
Forensic Sci Int ; 267: 16-24, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27525554

RESUMO

Crime scene investigations often rely on successful development of latent fingermarks for personal identification. In this context, exploring fundamental properties of latent fingermarks is vital for developing robust and more effective detection techniques. Here in a novel approach, PeakForce quantitative nanomechanical mapping (PF QNM) atomic force microscopy (AFM) has been used to study the variations in surface adhesion and topography of latent fingermark droplets over time. It was found that variation in adhesion was exhibited even across the surface of a single fingermark droplet, suggesting that individual droplets are heterogeneous in chemical composition on the nanoscale. The technique was successfully employed in observing the topographical variation of eccrine droplets, which has not been achieved using other optical microscopy techniques. In addition, the adhesion of fingermark droplets changed significantly as they aged. Propagation of a thin film of material from the fingermark ridges across the furrows, starting immediately after deposition, was captured in real-time, demonstrating the dynamic nature of the deposit. These results will aid in providing a more complete fundamental understanding of latent fingermark residue, allowing the more rational development of new detection techniques, especially those involving nanostructured materials.


Assuntos
Dermatoglifia , Microscopia de Força Atômica/métodos , Adulto , Glândulas Écrinas , Humanos , Pessoa de Meia-Idade , Suor , Fatores de Tempo
8.
Talanta ; 158: 368-374, 2016 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-27343617

RESUMO

The investigation of explosive events requires appropriate evidential protocols to recover and preserve residues from the scene. In this study, a central composite design was used to determine statistically validated optimum recovery parameters for double-base smokeless powder residues on steel, analysed using total vaporisation (TV) SPME/GC-MS. It was found that maximum recovery was obtained using isopropanol-wetted swabs stored under refrigerated conditions, then extracted for 15min into acetone on the same day as sample collection. These parameters were applied to the recovery of post-blast residues deposited on steel witness surfaces following a PVC pipe bomb detonation, resulting in detection of all target components across the majority of samples. Higher overall recoveries were obtained from plates facing the sides of the device, consistent with the point of first failure occurring in the pipe body as observed in previous studies. The methodology employed here may be readily applied to a variety of other explosive compounds, and thus assist in establishing 'best practice' procedures for explosive investigations.

9.
Talanta ; 148: 715-20, 2016 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-26653507

RESUMO

This paper presents a study into the chemical changes occurring within automotive clear coats as a result of environmental weathering, and their potential effect upon the characterisation of samples using infrared spectroscopy combined with chemometric modelling. Testing of three samples, collected from separate vehicles, exposed to the outside environment revealed no changes in model predictions over a 175 day period; however, incorrect predictions were observed following 435 days of exposure. Inspection of the corresponding infrared spectra revealed that these changes were likely due to the hydrolysis and photodegradation of polymer chains present in the clear coat, which were not observed in samples stored away from the outside environment over a one-year period. Analysis of previously weathered samples using synchrotron infrared microscopy found these changes occurred in a top-down fashion rather than within the bulk of the clear coat. This indicates that although weathering may affect the surface characterisation of clear coats over time, the targeting of deeper portions of the clear coat layer may still provide useful information as to the identity of the vehicle.

10.
Talanta ; 148: 721-8, 2016 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-26653508

RESUMO

It can be very challenging to recover explosives traces from porous surfaces, such as clothing and car seats, compared to non-porous surfaces. The contact heater has been developed as a novel instrument designed to recover explosives traces from porous surfaces. Samples are taken by heating and drawing air across a surface, with the air flowing through a sampling cartridge containing adsorbent polymer beads, which act to trap any recovered explosive material. Any collected explosive can then be eluted from this cartridge using a solvent, prior to analysis. This paper outlines work performed to evaluate the usefulness of the contact heater with regards to the recovery of explosives traces from porous materials. Ethylene glycol dinitrate (EGDN) and triacetone triperoxide (TATP) were chosen as two representative explosives for this study. Quantification was performed using GC-MS for EGDN and LC-MS/MS for TATP. Different sampling temperatures, sampling times and elution solvents were investigated. Recovery was trialled from leather, carpet and denim. Recoveries of up to 71% were obtained following optimisation. It was also possible to recover TATP from fabrics exposed to TATP vapour in a vapour-laden jar up to two hours after exposure. The contact heater therefore appears to be a very useful tool for the recovery of explosives traces from porous materials.


Assuntos
Substâncias Explosivas/análise , Medicina Legal/métodos , Temperatura Alta , Espectrometria de Massas em Tandem/métodos , Medicina Legal/instrumentação , Porosidade , Propriedades de Superfície , Espectrometria de Massas em Tandem/instrumentação
11.
Forensic Sci Int ; 257: 20-28, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26282509

RESUMO

Dimethylaminocinnamaldehyde was re-evaluated as a wet contact reagent for the treatment of latent fingermarks on porous substrates. A new formulation (consisting of 0.028 g p-dimethylaminocinnamaldehyde, 0.84 mL glacial acetic acid, 6.2 mL ethyl acetate and 0.993 L 40-60 °C petroleum spirits) provides quick, sensitive and robust luminescent ridge detail within 3 h of treatment on both plain and thermal paper. Comparisons to existing formulations indicate improved visualisation and/or a more efficient process.


Assuntos
Cinamatos/química , Dermatoglifia , Luminescência , Cloretos , Humanos , Indanos , Indicadores e Reagentes/química , Estrutura Molecular , Papel , Porosidade , Espectrometria de Fluorescência , Compostos de Zinco
12.
Chem Commun (Camb) ; 50(25): 3341-3, 2014 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-24535380

RESUMO

Nile blue A in aqueous solution undergoes spontaneous hydrolysis to the photoluminescent compound Nile red. This reagent provides a simple and safe approach to the detection of latent fingermarks on porous and non-porous surfaces.

13.
Talanta ; 118: 156-61, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24274283

RESUMO

Synchrotron FTIR microspectroscopy was used to characterise and assess the chemical diversity of electrocoat primer, primer surfacer and basecoats of automotive paint samples from 75 vehicles representing a range of international car manufacturers. Significant diversity was found in the synchrotron FTIR data from the primer surfacer coats. Classification using principal component analysis revealed 14 discrete groups, which could be associated with the country of manufacture, the specific manufacturer and manufacturing plant, the year of manufacture of the vehicle and in some instances the number of layers in the paint system. The model generated from the primer surfacer was significantly more discriminating than a previous model generated from FTIR analysis of clear coats of the same vehicles. Analysis of the primer surfacer also avoids issues of possible environmental degradation and component migration seen with FTIR analysis of automotive clear coats. Providing such information concerning vehicle origin would aid in the development of investigative leads from the analysis of questioned automotive paint samples located at the scene of a crime or on the body/clothing of a hit and run victim.


Assuntos
Automóveis , Medicina Legal , Pintura/análise , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Síncrotrons , Humanos
14.
Forensic Sci Int ; 228(1-3): 165-9, 2013 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-23462650

RESUMO

Synchrotron infrared chemical imaging was employed to examine and assess the extent of interlayer component migration within multilayer automotive paint samples, with a particular emphasis on the cross-linking additive melamine. Two dimensional infrared chemical images revealed that melamine consistently diffuses in select paint samples from the underlying basecoat into the outermost clear coat layer. Pigments from the basecoat were also found to migrate into the adjoining layers. This is significant as the relative abundance of both melamine and pigments will vary greatly depending upon the region of the layer analysed. This component migration will undoubtedly impact the information gleaned from a questioned sample via library searching software or multivariate statistics. As a result, appropriate analytical protocols will need to be utilised to mitigate the effects of interlayer pigment and melamine diffusion, so as to afford a true representation of the composition of the coating for forensic identification purposes.

15.
Appl Spectrosc ; 64(10): 1122-5, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20925981

RESUMO

Clear coats have been a staple in automobile paints for almost thirty years and are of forensic interest when comparing transferred and native paints. However, the ultraviolet (UV) absorbers in these paint layers are not typically characterized using UV microspectrophotometry, nor are the results studied using multivariate statistical methods. In this study, measurements were carried out by UV microspectrophotometry on 71 samples from American and Australian automobiles, with subsequent chemometric analysis of the absorbance spectra. Sample preparation proved to be vital in obtaining accurate absorbance spectra and a method involving peeling the clear coat layer and not using a mounting medium was preferred. Agglomerative hierarchical clustering indicated three main groups of spectra, corresponding to spectra with one, two, and three maxima. Principal components analysis confirmed this clustering and the factor loadings indicated that a substantial proportion of the variance in the data set originated from specific spectral regions (230-265 nm, 275-285 nm, and 300-370 nm). The three classes were well differentiated using discriminant analysis, where the cross-validation accuracy was 91.6% and the external validation accuracy was 81.1%. However, results showed no correlation between the make, model, and year of the automobiles.

16.
J Forensic Sci ; 55(2): 308-14, 2010 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-20070470

RESUMO

In this paper, we report the results of our preliminary studies into chemical characterization of the fluids produced during decomposition in the absence of a soil matrix. Pig (Sus domestica) carcasses were used to model the human decomposition process in two separate locations, Western Australia (Perth) and Canada (Oshawa). Analysis involved simple dilution and filtration of the decomposition fluids followed by gas chromatography-mass spectrometry. Several previously unreported compounds were detected in the decomposition fluid samples during the trials, including benzeneacetic acid, benzenepropionic acid, 2-piperidone, and isocaproic acid. Possible biosynthetic pathways for some of the compounds produced are proposed. Further research trials are required, particularly in the presence of soil matrices.


Assuntos
Ácidos Graxos/análise , Mudanças Depois da Morte , Animais , Austrália , Biomarcadores/análise , Dípteros , Comportamento Alimentar , Antropologia Forense , Patologia Legal , Cromatografia Gasosa-Espectrometria de Massas , Ontário , Sus scrofa , Temperatura
17.
Anal Chim Acta ; 652(1-2): 128-42, 2009 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-19786173

RESUMO

The introduction of ninhydrin treatment as a chemical technique for the visualisation of latent fingermarks on porous surfaces revolutionised approaches to forensic fingermark examination. Since then, a range of amino acid sensitive reagents has been developed and such compounds are in widespread use by law enforcement agencies worldwide. This paper reviews the development and use of these reagents for the detection of latent fingermarks on porous surfaces. A brief overview is provided, including an historical background, forensic significance, and a general approach to the development of latent fingermarks on porous surfaces. This is followed by a discussion of specific amino acid sensitive treatments.


Assuntos
Aminoácidos/química , Ciências Forenses/métodos , Aminoácidos/análise , Compostos Aza/química , Indanos/química , Glicosídeos Iridoides , Iridoides/química , Naftoquinonas/química , Ninidrina/análogos & derivados , Ninidrina/química , Propriedades de Superfície
18.
Chem Commun (Camb) ; (30): 3513-5, 2008 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-18654697

RESUMO

Lawsone (2-hydroxy-1,4-naphthoquinone) reacts with latent fingermark deposits on paper surfaces to yield purple-brown impressions of ridge details which are also photoluminescent; this compound represents the first in a completely new class of fingermark detection reagents.

19.
J Forensic Sci ; 52(5): 1111-4, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17767657

RESUMO

The use of tris(2,2'-bipyridyl) ruthenium (III) as a chemiluminescent spray reagent spot-test for heroin is discussed. Two forms of the reagent are investigated an aqueous and an anhydrous where both were found to give vastly different results. The aqueous reagent giving slow, low intensity chemiluminescence whilst the anhydrous reagent gave a fast, bright response in the presence of 3,6-diacetylmorphine. The anhydrous reagent is less sensitive the slow, intensity response is characteristic of only two opiates tested 3,6-diacetylmorphine and 3-monoacetylmorphine.

20.
Anal Chim Acta ; 597(1): 19-23, 2007 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-17658308

RESUMO

We have combined high-performance liquid chromatography (HPLC) separations using a monolithic column with acidic potassium permanganate and tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence detection in a rapid and highly sensitive method to monitor the process of extracting opiate alkaloids from Papaver somniferum. Due to the high flow rates allowed with the monolithic column and the inherent selectivity of the chemiluminescence reactions, the four predominant alkaloids--morphine, codeine, oripavine and thebaine--were determined in less than 2 min. The results obtained with numerous process samples compared favourable with those of the standard HPLC methodology. Limits of detection were 1x10(-10) M, 5x10(-10) M, 5x10(-10) M and 1x10(-9) M, for morphine, codeine, oripavine and thebaine, respectively.


Assuntos
Alcaloides Opiáceos/análise , Papaver/química , Cromatografia Líquida de Alta Pressão , Medições Luminescentes , Compostos Organometálicos/química , Permanganato de Potássio/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA