Forensic analytical chemist

Regarding tissues and body fluids to be analyzed, blood and urine serve most frequently as source material, although the interest of forensic analytical chemists can be easily extended to other specimens (e.g., saliva, bile, or vitreous humor). A tissue that has attracted a lot of inter-... 

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... 

In this respect, current state-of-the-art ends up in a draw. This book makes a substantial contribution to the current literature on the analytics of polymer additives, follows up an earlier industrial tradition and lays a foundation for the future. It will be of great value to a broad readership comprising industrial and academic (analytical) chemists, polymer scientists and physicists, technologists and engineers, and other professionals involved in R D, production, use and reuse of polymers and additives in all areas of application, including manufacturers, formulators, compounders, end users, government legislators and their staff, forensic scientists, etc. 

Informed debate and decisions on such important matters as the depletion of the ozone layer, acid rain and the quality of waterways all depend on the data provided by analytical chemists. Forensic evidence also often depends on chemical measurements. National and international trade are critically dependent on analytical results. Chemical composition is often the basis for the definition of the nature of goods and tariff classification. In all of these areas not only is it important to get the right answer but it is essential that the user of the results is confident and assured that the data are truly representative of the sample and that the results are defendable, traceable and mutually acceptable by all laboratories. 

Analytical chemistry impacts on every aspect of modern life. The food and drink we consume is tested for chemical residues and appropriate nutritional content by analytical chemists. Our health is monitored by chemical tests (e.g. cholesterol, glucose), and international trade is underpinned by measurements of what is being traded (e.g. minerals, petroleum). Courts rely more and more on forensic evidence provided by chemistry (e.g. DNA, gun-shot residues), and the war on terrorism has caused new research into detection of explosives and their components. Every chemical measurement must deliver a result that is sufficiently accurate to allow the user to make appropriate decisions it must be fit for purpose. 

This situation presents a challenge to the analytical chemist, namely, which substance is the most appropriate for measurement. The answer would seem to depend on the origin of the sample as well as the ingenuity of the chemist in developing a sensitive, specific assay. In the case of forensic assays, legalistic considerations will probably specify which substances are to be measured. If the term "under the influence of" is invoked, the levels of "active" metabolites will also have to be measured before judgment can be passed. 

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. 

The first problem confronting our forensic chemist may be separation. Police will separate witnesses, taking them into individual rooms to hear their accounts to avoid interference from other principals. Likewise, an analytical chemist will strive to separate the components of an unknown mixture so that the separate materials can be analyzed without... 

Analytical chemists also make important contributions to fields as diverse as forensics, archaeology, and space science. 

For practicing analytical chemists and on-the-job apphcations, it is especially important to use the lab notebooks for entering observations and measurements directly. Complete documentation is essential for forensic or industrial laboratories for legal or patent considerations. In industrial research labs, the notebook must generally be signed (witnessed) and dated by another person familiar with the work to assure legal patent priority if applicable. 

The sample techniques just described are designed for collection of transmission (absorption) spectra. This had been the most common type of IR spectroscopy, but it was limited in its applications. There are many types of samples that are not suited to the conventional sample cells and techniques just discussed. Thick, opaque solid samples, paints, coatings, fibers, polymers, aqueous solutions, samples that cannot be destroyed such as artwork or forensic evidence samples, and hot gases from smokestacks—these materials posed problems for the analytical chemist who wanted to obtain an IR absorption spectrum. The use of reflectance techniques provides a nondestructive method for obtaining IR spectral information from materials that are opaque, insoluble, or cannot be placed into conventional sample cells. In addition, IR emission from heated samples can be used to characterize certain types of samples and even measure remote sources such as smokestacks. In reflectance and emission, the FTIR spectrometer system is the same as that for transmission. For reflectance, the sampling accessories are different and in some specialized cases contain an integral detector. The heated sample itself provides the light for emission measurements therefore, there is no need for an IR source. There may be a heated sample holder for laboratory emission measurements. 

The solvent extraction method with which the analytical chemist is most familiar involves placing both liquid phases in a separatory funnel and agitating by hand to effect the partition due to issues of contamination control and limited solution volumes, this implementation is little used in nuclear forensic analysis. Often, phases are mixed in a capped centrifuge cone using a vortex mixer this is particularly convenient in a gloved box, where the loss of manual dexterity impedes the manipulation of a separatory funnel and stopcock. Phase separation is facilitated through the use of a centrifuge. 

Practising analytical chemists face both qualitative and quantitative problems. As an example of the former, the presence of boron in distilled water is very damaging in the manufacture of microelectronic components - Does this distilled water sample contain any boron . Again, the comparison of soil samples is a common problem in forensic science - Could these two soil samples have come from the same site . In other cases the problems posed are quantitative. How much albumin is there in this sampie of biood serum , How much lead in this sample of tap-water , This steei sampie contains smaii quantities of chromium, tungsten and manganese - how much of each these are typicai exampies of single-component or multiple-component quantitative anaiyses. 

Robert VN lhelm Bunsen (1811-1899), mentioned in an earlier Historical Evidence, was a true analytical chemist and would have ix) doubt made an excellent forensic chemist He was nothing if not practical and was quoted as saying "A single determination of one fact is more valuable than the most beautifully constructed theory."... 

Review articles allow even the busiest forensic chemist the opportunity to find summaries of current research. The journal Analytical Chemistry publishes a semiarmual review of forensic science that emphasizes forensic analytical chem-istry. This publication contains extensive and current research in drug analysis, as well as in many other aspects of forensic chemistry. For drug analysis, the DEA has published a recent extensive review of articles covering 1992-2002. As part of the Microgram Journal, this review is available online. 

In the development of analytical methods one has to consider also cases where a fast response is required, e.g. clinical and forensic chemists or toxicologists need methods which yield results in a few minutes or hours to allow a fast response in cases of poisoning. In this event, accurate quantitative results may be of less importance, but the time from sampling to result may be lifesaving, whereas the throughput (i.e. number of analyses per day) is not so much of concern. 

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). 

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