Quantitative analysis forensic sciences

See also Bioluminescence. Chemiluminescence Liquid-Phase. Electrophoresis Blotting Techniques. Enzymes Immobilized Enzymes Enzyme Assays. Fluorescence Quantitative Analysis. Forensic Sciences Blood Analysis. Immunoassays Overview. Immunoassays, Applications Clinical Forensic. Immunoassays, Techniques Radioimmunoassays. 

Reilly, C.A., Crouch, D.J. and Yost, G.S. (2001) Quantitative analysis of capsaicinoids in fresh peppers, oleoresin capsicum and pepper spray products. Journal of Forensic Sciences 46(3), 502-509. 

Analytical chemists are employed in industrial research, academic research, and forensic science. Their job usually involves two different types of work qualitative analysis and quantitative analysis. A qualitative analysis determines which substances are present. A quantitative analysis determines how much of a specific substance is present. 

Again, of course, if this approach is used, full forensic science principles should be applied. The packaging should be described and documented and its condition noted. If the analysis is to be quantitative, then the material should be dried to constant weight. Both the fresh weight and the dry weight should be recorded. 

The potentiai for using HPLC in forensic science laboratories was recognised when the technique was in its infancy. This interest arose because of the difficulties encountered with the analysis of basic drugs, and it was soon to be appreciated that HPLC offered certain advantages over gas chromatography (GC). Once it was established that reproducible quah-tative and quantitative analysis could be performed in several minutes there was a keeimess to determine if HPLC could be used to solve other analytical problems experienced by the forensic scientist. 

When a sample is presented to the analyst, the first requirement is to ascertain what the sample is and the substances present for reasons of safe handling, and to find out whether it has been contaminated, accidentally or maliciously. An important part of the analyst s task is the determination of how much of a particular component is present and such a requirement offers a greater challenge to the analyst. This part of the task falls into the realm of quantitative analysis and requires the application of sophisticated techniques used by intelligent and well-trained personnel. With increasing demands for higher standards in the quality of raw materials and finished products - be it foods, pharmaceuticals, industrial, forensics, or whatever - analytical science plays a very important role in ensuring that these standards are maintained. 

A major work for all forensic science laboratories is directed to the analysis of drugs of abuse. GC plays a prominent role in analyzing these exhibits, both for identification of the particular drug (qualitative analysis) and for the determination of the amount of pure drug in the sample (quantitative analysis). 

Forensic science is the application of science to problems encountered in the courts of law. Forensic laboratories specialize in the analysis, identification, and interpretation of physical evidence. Typically, analyses performed in such laboratories are concerned with determining (1) component identification of a sample, (2) quantitation or purity of sample components, or (3) similarities or differences between two or more samples. With automated instrumentation widely available, highly specific mass spectrometry (MS)-based technologies are now the most valuable tools used to achieve these desired analytical goals. 

Figure 5 Mass spectra and chemical structures of secobarbital (A), Hs-secobarbital (B), and C4-secobarbital (C) (All as methyl-derivatives). (Reproduced with permission from Chang W-T, Smith J, and Liu RH (2002) Isotopic analogues as internal standards for quantitative GC/MS analysis - molecular abundance and retention time difference as interference factors. Journal of Forensic Sciences 47 873-881.)...

Chang WT, Smith J, and Liu RH (2002) Isotopic analogs as internal standards for quantitative GC/MS analysis -molecular abundance and retention time difference as interference factors. Journal of Forensic Science 47 873-881. 

In the early history of chemistry, all chemists found themselves performing analyses of one kind or another. In more recent times, analytical procedures have become much more sophisticated, and analytical chemistry has in consequence become a specialised branch of the subject. The skills of the analyst are now utilised not only by other chemists, but also by those carrying out investigations in fields such as forensic science, environmental science and the quality control of all manner of products. Some analytical techniques (for example the quantitative elemental analysis of organic compounds and the investigation of molecular structure by physical methods) have been considered in earlier chapters. 

Forensic chemistry is applied analytical chemistry. If that were the extent of it, however, there would be no need for a separate course or textbook on the subject. What then makes forensic chemistry unique Arguably, it is the same consideration that defines forensic science as a distinct discipline the skill, art, and science of comparison. Analytical chemistry encompasses qualitative and quantitative analysis, but forensic chemistry adds comparative analysis to the task list. For example, spectroscopic analysis can quickly determine whether a fiber is made of nylon or a piece of plastic is polyethylene. These are analytical descriptors that answer analytical questions such as "What is it " and "How much of it is there " Analytical chemistry provides qualitative... 

Centini, F., et al. "Quantitative and Qualitative Analysis of MDMA, MDEA, MA and Amphetamine in Urine by Headsjjace/Solid Phase Micro-extraction (SPME) and GC/MS." Forensic Science International 83 (19%), 161-166. 

Stockham PC, Partridge EL. Application of quadrupole time-of-flight—mass spectrometry to the quantitative analysis of basic drugs. Poster presentation, 20th International Symposium on the Forensic Sciences, 5—9 September 2010, Sydney, Australia. 

Sachs, H. and Raff, I. (1993) Comparison of quantitative results of drugs in human hair by GC-MS, in Forensic Science International, vol. 63, Special Issue Hair Analysis as a Diagnostic Tool for Drugs of Abuse Investigation (ed P. Saukko), Elsevier, Amsterdam, pp. 207-216. 

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