Analysis forensic samples

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. 

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). 

Although comprehensive two-dimensional gas chromatography has not been applied to any great extent in forensic analysis, the technique shows great promise when samples or sample matrices are complex. For example, when oil is spilled into waterways, assigning responsibility for the economic and environmental damage is often difficult. Gaines et al. employed comprehensive two-dimensional GC in the forensic analysis of samples collected at oil-spill sites and were able to obtain results which were comparable to those obtained by classical methods (39). This article also... 

C03-0132. Police officers confiscate a packet of white powder that they believe contains heroin. Purification by a forensic chemist yields a 38.70-mg sample for combustion analysis. This sample gives 97.46 mg CO2 and 20.81 mg H2 O. A second sample is analyzed for its nitrogen content, which is 3.8%. Show by calculations whether these data are consistent with the formula for heroin, C21 H22 NO5. ... 

Whilst for the analysis of plant material for cannabinoids both GC and HPLC are commonly used, in analytical procedures the employment of GC-based methods prevails for human forensic samples. Nonetheless, the usage of HPLC becomes more and more of interest in this field especially in combination with MS [115-120]. Besides the usage of deuterated samples as internal standards Fisher et al. [121] describe the use of a dibrominated THC-COOH (see 7.5). The usage of Thermospray-MS and electrochemical detection provide good performance and can replace the still-used conventional UV detector. Another advantage in the employment of HPLC rather than GC could be the integration of SPE cartridges, which are needed for sample preparation in the HPLC-system. 

TOF-SIMS has been employed for the characterization of a wide range of materials, including metallic, salt, organometallic, organic, and polymeric substances, as well as for electronics, catalysts, and forensic samples. The ability to image molecular ions with submicrometer spatial resolution makes TOF-SIMS well suited to analysis of pharmaceuticals and biological cells, as well as for use in biotechnology and molecular electronics. 

For high reproducibility of migration times and peak areas the sample matrix should be identical for all samples analyzed together. While this is challenging for forensic applications where analytes in whole blood or urine are determined, this requirement can be fulfilled easily in pharmaceutical analysis. After sample preparation of the drug product, the sample matrix is similar in most cases. The composition of blood or urine depends on its source. Thus, the changing sample matrix has more impact on the quality of the CE analysis. 

Provided a sample of DNA can be obtained, a restriction analysis can be carried ont. A match between the restriction fragments from a sample of DNA left at the scene of a crime and that of a snspect is a valnable tool in forensic science. The usefulness of this techniqne is increased enormously by combining it with the polymerase chain reaction, since the amount of DNA extracted from a very small amount of tissue can be increased enormonsly, providing enough for a restriction analysis. Tissne samples as small as a single cell, a hair, a drop of sahva, a piece of dandruff or a smear of semen are snfflcient to prodnce enough DNA. It has produced a revolution in forensic science. However, caution must be applied to interpretation of the results for... 

Clearly, the commercial or consultancy laboratory that tests sub-samples of a marketed product worth millions of pounds, or assesses the purity of pharmaceuticals, or analyses forensic samples, must have far higher levels of both accuracy and verifiability than student practical classes. There should, however, always be an effort to produce the most accurate and reliable results within the constraints of the laboratory facilities available, otherwise a lax attitude will produce work of doubtful interpretation that could mislead others, as well as giving little job satisfaction. Several books, which are more suited to the commercial sector, have been written on the quality of laboratory analysis, however some quality assurance practices could be beneficial in the smaller laboratory. A useful open-learning style book on basic concepts of quality in the analytical laboratory has been co-authored by staff at the Laboratory of the Government Chemist (Crosby et ai, 1995). 

Soil for microbiological studies is normally collected from the plow depth (10-23 cm at Rothamsted, United Kingdom, but it may vary elsewhere) and 0-10 cm depth for grassland or forest soils. For forensic analysis the sample depth will be decided by the nature of the crime scene. However, maximum biological activity will be adjacent to a corpse and will decline with depth... 

Horrocks, M. (2004). Sub-sampling and preparing forensic samples for pollen analysis. J. Forensic Sci. 49,1024-1027. 

The sequence of events associated with FDR examination is usually as follows the initial incident, apprehension of suspects, transporting of suspects to police station, sampling of suspects at police station (swabs of hands, face, head hair, and seizure of clothing), submission of items to the laboratory, sampling of clothing at the laboratory, sample preparation, analysis of samples, interpretation of results, preparation of statement of witness report, and the presentation of forensic evidence in court. 

The criteria for the interpretation of cocaine concentrations in biological samples and their relation to the cause of death has been comprehensively reviewed (234). The importance of scene investigation, forensic autopsy, and forensic sampling for drug analysis has been discussed, with particular emphasis on the need to use appropriate blood preservatives and interpretation of the half-life and concentrations of cocaine and its metabolites, benzylec-gonine and ethylcocaine, in combined cocaine + alcohol abuse. 

Biomedical and forensic analysis are dealt with together in this chapter since for both of these application areas, the chromatographer encounters very similar types of samples. Biomedical analysts work with samples of biological fluids which is also the type of sample with which the forensic analyst primarily works. Other types of forensic samples are also often of a similar nature, in that low levels of analyte in a complex matrix are involved. However, in looking at biomedical and forensic analysis together, it will be observed that by virtue of the differences in analytical problems posed, the nature of the HPLC carried out may often be quite different. 

Applications of SPE include clinical analysis, pharmaceuticals, food analysis, environmental analysis, agrochemicals, forensic samples, etc. 

Following the approaches described above, reliable, reproducible, and linear band patterns can be achieved using ULPAGIF for genetic marker typing as well as for most isoelectric focusing protein analyses. This is of particular concern for laboratories with heavy case loads. Time and expenses taken to rerun samples may be prohibitive. Further, when sample size is a limiting factor, as can be the case for forensic samples of supplies of extremely rare variants, multiple tests to obtain an analysis may prove to be impossible. If care is taken, seldom will a gel have to be rerun. 

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