Forensic sources

EDXRF has been used for comparison of the elemental composition of some 100 carpet fibres (both automotive and residential) for forensic source classification [260]. SEM-EDS is too insensitive for this... 

FIGURE 6.6 An iodine enhanced fingerprint. (Photo provided courtesy of Forensics Source 2010.) Thanks to Eric Schellhom, director of marketing, and Floyd Wilson who developed a print on an outside rough surface as a severe demonstration as requested. Close examination reveals clear print lines suitable for computer analysis. 

The study of obsidian by NAA has proved to be particularly fruitful because of the relatively limited number of sources and the extent to which it was traded (Beardsley et al. 1996, Cook 1995, Darling and Hayashida 1995, Kuzmin et al. 2002, Leach 1996). Studies have also extended to include other volcanic materials such as pumice (Bichler et al. 1997, Peltz et al. 1999). NAA has also been used for the analysis of flint as OES is insensitive and not reproducible due to the effect of the high silica content, and AAS requires significant sample preparation (Aspinall and Feather 1972). The wide range of appropriate materials extends to organic materials such as human bone (Farnum et al. 1995), and its exceptional sensitivity to trace elements has led to its wide use in geochemistry (for example in determining trace [ppb] contaminants in waters) and more recently in forensic chemistry. 

Lundegard, P. D., Haddad, R., and Brearley, M., 1998, Methods Associated with a Large Gasoline Spill Forensic Determination of Origin and Source Environmental Geosciences, Vol. 5, No. 2, pp. 69-77. 

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. 

S. Caldera, D. Gardebas, F. Martinez and S. Khong, Organic explosives analysis using on column-ion trap EI/NICI GC-MS with an external source , J. Forensic Sci., 49 No. 5 (2004) 1005-1008. 

Varying residual solvent profiles can be used to identify dmg substance samples obtained from different sources [16] for forensic purposes. 

However, some obstacles still have to be removed before HPLC-MS is fully accepted as a routine technique in the forensic labs. First of all the cost of equipment is still high, despite the reduction trend in the last years, as compared to GC-MS. Second, some problems have to be tackled, i.e., the susceptibility of ion sources (and particularly ESI) to matrix effects on analyte s ionization efficiency (suppression or enhancement) and the scarce reproducibility of MS fragmentation. The third obstacle is actually the other side of the coin of versatility the wide choice of technical alternatives makes HPLC-MS still far from being a highly standardized, one-button technique as GC-MS. 

Source The American Journal of Forensic Medicine and Pathology Official Pubhcation of the National Association of Medical Examiners. 

Gas chromatography is one of the most active areas of analytical chemistry, but many references in GC will be found in sources other than just chromatography or analytical chemistry. Thus, literature searches should take one to the journals on topics where GC may be utilized, for example, journals of biochemistry, organic chemistry, physical chemistry, catalysis, environmental studies, drug analysis, forensic chemistry, petroleum chemistry, inorganic chemistry. 

More recently, the forensic application of DNA testing has dramatically enhanced the ability to determine the source of a blood sample. Two procedures are in forensic use restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR). 

Flannagan, L.M., Butts, J.D., and Anderson, W.H., Fentanyl patches left on dead bodies — potential source of drug for abusers, J. Forensic Set, 41, 320, 1996. 

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