Chemistry forensic

Forensic science is an applied science having a focus on practical scientific issues that come up during criminal investigations or at trial. Some components ate unique to the field because it is conducted within the legal arena. Forensic science issues in chemistry and biochemistry in criminal investigations are discussed herein. There are a host of other forensic science areas, eg, forensic medicine, forensic dentistry, forensic anthropology, forensic psychiatry, and forensic engineering, any of which may overlap with forensic chemistry. 

Forensic scientists work with physical evidence, ie, data presented to a court or jury in proof of the facts in issue and which may include the testimony of witnesses, records, documents or objects. Physical evidence is teal or tangible and can HteraHy include almost anything, eg, the transient scent of perfume on the clothing of an assault victim the metaboHte of a dmg detected in the urine of an individual in a driving-under-the-influence-of-dmgs case the scene of an explosion or bullets removed from a murder victim s body. 

Historically, physical evidence has taken on increasing importance in criminal matters. Court decisions have consistentiy looked askance at a defendant s admissions of guilt and even question eyewitness testimony. Physical evidence has traditionally been viewed as impartial and unbiased, and not subject to the problems associated with confessions made by an accused or the testimony of witnesses. 

Physical evidence serves two purposes. In some cases it is used to prove a component or element of a crime. Eor example, in a case involving trafficking in cocaine [50-36-2] the prosecutor must prove that the white powder found in the criminal s possession was cocaine (Table 1). The forensic chemist tests the substance and issues a report. If the powder is methamphetamine [537-46-2] the charge must be amended. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

Methyl tert-butyl ether (MTBE) 1980sa 

Current EPA analytical methods do not allow for the complete speciation of the various hydrocarbon compounds. EPA Methods 418.1 and 8015 provide the total amount of petroleum hydrocarbons present. However, only concentrations within a limited hydrocarbon range are applicable to those particular methods. Volatile compounds are usually lost, and samples are typically quantitated against a known hydrocarbon mixture and not the specific hydrocarbon compounds of concern or the petroleum product released. By conducting EPA Method 8015 (Modified) using a gas chromatograph fitted with a capillary column instead of the standard, hand-packed column, additional separation of various fuel-ranged hydrocarbons can be achieved. 

Several methodologies can be used to identify not only crude or refined product type, but also the brand, grade, and, in some instances, the source crude. The petroleum industry has yielded conventional methods for the characterization of refined products. The simplest is the routine determination of API gravity and development of distillation curves where NAPL is present. More sophisticated methods include gas chromatography and statistical comparisons of the distribution of paraffinic or n-alkane compounds between certain C-ranges. With increased degradation and decomposition, the straight-chain hydrocarbons ( -alkanes) become less 

Department of Agriculture (1994). Complete Guide to Home Canning. Washington, DC U.S. Government Printing Office. 

National Center for Home Food Preservation. Available from http //www.uga.edu /nchfp/ . 

Hippocrates Greek physician of fifth century b.c.e. known as Father of Medicine  

Physical evidence collected at crime scenes is sealed in special containers to prevent contamination and degradation and is catalogued carefully. A chain of custody is established and documented as the evidence is sent to a forensic laboratory. At the laboratory, the evidence is examined by personnel trained in one of several fields Forensic serologists examine body fluids, forensic pathologists examine human remains, firearms technicians classify and test firearms and explosives, and forensic chemists determine the composition and identity of materials. 

Every chemist is schooled in general, organic, and analytical chemistry, but forensic chemists also specialize in specific areas of expertise. For example, an inorganic chemist may examine traces of dust by using micro-chemistry to identify the chemical composition of tiny particles. Another chemist might employ thin-layer chromatography during the analysis of 

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The use of DRIFTS for the characterization of surfaces has to date been limited, but has recently been used for applications in fields as diverse as sensors development [12], soils science [13], forensic chemistry [14], corrosion [15], wood science [16] and art [F7]. Given that there is in general no reason for preferring transmission over difilise reflectance in the study of high-area powder systems, DRIFTS is likely to become much more popular in the near fiiture. 

Analytical chemists work to improve the ability of all chemists to make meaningful measurements. Chemists working in medicinal chemistry, clinical chemistry, forensic chemistry, and environmental chemistry, as well as the more traditional areas of chemistry, need better tools for analyzing materials. The need to work with smaller quantities of material, with more complex materials, with processes occurring on shorter time scales, and with species present at lower concentrations challenges analytical... 

The applications of Beer s law for the quantitative analysis of samples in environmental chemistry, clinical chemistry, industrial chemistry and forensic chemistry are numerous. Examples from each of these fields follow. 

Forensic chemistry Forensics Forensic stijdies Forestry... 

One of the particulady challenging aspects of the work in a museum laboratory is the enormous variety of problems encountered. Every object examined is unique and for each the questions to be answered differ. Thus the museum laboratory most closely resembles, if anything, the forensic laboratory, and many of the methodologies employed are common (see Forensic chemistry). 

Microscopy (qv) is appHed when particle identification and, perhaps, shape evaluation ate important in addition to size. Shape characterization is used in the abrasives (qv) industries, pollution or contamination assessment, and forensic studies (see Forensic CHEMISTRY). 

Thermal neutron activation analysis has been used for archeological samples, such as amber, coins, ceramics, and glass biological samples and forensic samples (see Forensic chemistry) as weU as human tissues, including bile, blood, bone, teeth, and urine laboratory animals geological samples, such as meteorites and ores and a variety of industrial products (166). 

An example of a classification problem ia which feature weighting and selection was important comes from forensic chemistry (qv). A classification method was needed to determine the paper grade and manufacturer of a paper scrap found at the scene of a crime. In this study, 119 sheets of paper (qv) representing 40 different paper grades and nine manufacturers were obtained (25). The objects were then the paper samples, and the variables consisted of... 

Chromatography is a technique for separating and quantifying the constituents of a mixture. Separation techniques are essential for the characterization of the mixtures that result from most chemical processes. Chromatographic analysis is used in many areas of science and engineering in environmental studies, in the analysis of art objects, in industrial quahty control (qv), in analysis of biological materials, and in forensics (see Biopolymers, analytical TECHNIQUES FiNE ART EXAMINATION AND CONSERVATION FoRENSic CHEMISTRY). Most chemical laboratories employ one or more chromatographs for routine analysis (1). 

The use of agarose as an electrophoretic method is widespread (32—35). An example of its use is in the evaluation and typing of DNA both in forensics (see Forensic chemistry) and to study heritable diseases (36). Agarose electrophoresis is combined with other analytical tools such as Southern blotting, polymerase chain reaction, and fluorescence. The advantages of agarose electrophoresis are that it requires no additives or cross-linkers for polymerization, it is not hazardous, low concentration gels are relatively sturdy, it is inexpensive, and it can be combined with many other analytical methods. 

Gerichte. judicial, forensic, legal. amt, n. court, tribunal. -amtmann, m. judge, barkeit, /. jurisdiction, -chemie, /. forensic chemistry, -chemiker, m. forensic chemist legal chemist, -hof, m. court, tribunal, -rat, m. judge counselor. 

In the modern forensic chemistry laboratory (Figure B) arsenic is detected by analysis of hair samples, where the element tends to concentrate in chronic arsenic poisoning. A single strand of hair is sufficient to establish the presence or absence of the element. The technique most commonly used is neutron activation analysis, described in Chapter 19. If the concentration found is greater than about 0.0003%, poisoning is indicated normal arsenic levels are much lower than this. 

The currently most important fields of application of thin-layer chromatography be seen in Fig. 1. The proportion of publications in the fields of pharmacy and vironmental analysis has increased over that in previous years. There has also beer appreciable increase in the fields of clinical and forensic chemistry and in biochemis... 

Gennaro, M.C., Abrigo, C., and Cipolla, J., High-performance liquid chromatography of colours and its relevance in forensic chemistry, J. Chromatogr., 674, 281, 1994. 

Nollet, L.M.L., Food Analysis by HPLC, 2nd ed., Marcel Dekker, New York, 2000. Gennaro, M.C., Abrigo, C., and CipoUa, G., HPLC analysis of food colors and its relevance in forensic chemistry, J. Chromatogr. A, 674, 281, 1994. Gratzfeld-Huesgen, A. and Schuster, R., HPLCfor Food Analysis A Primer, Hewlett-Packard Company, Palo Alto, CA, 1996. 

High-Performance Liquid Chromatography in Forensic Chemistry, edited by Ira S. Lurie and John D. WIttwer, Jr. 

Z. Takats, J. M. Wiseman and R. G. Cooks, Ambient mass spectrometry using desorption electrospray ionization (DESI) instmmentation, mechanisms and applications in forensics, chemistry, and biology, J. Mass Spectrom., 40, 1261 1275 (2005). 

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