Forensic analysis

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. 

Within a forensic science laboratory, the analytical problems are often very different to those found in other laboratories. Extremely small and often aged samples, complex matrices and an extensive range of analytes are encountered by the forensic scientist and the success of any HPLC method is often very dependent upon the selectivity and/or sensitivity of the system. General developments in column and detector technology have played a major role in improving both these criteria and hence increasing the number of forensic appUcations of HPLC. 

Selectivity, the ability to isolate a particular analyte or separate a number of components within a mixture, has improved dramatically through the development of bonded-phase column packing materials for reversed-phase, ion-exchange and ion-pair chromatography. More recently, forensic laboratories have been introducing polymeric packing materials because of their selectivity and other physical and chemical properties which are more desirable than those of silica-based materials. 

In its broadest sense, selectivity has also been achieved through the development of ion chromatography and indirect photometric detection. Apart from opening up a completely new application of HPLC these provide highly selective techniques for the analysis of inorganic and organic ions. 

Sensitivity, which is defined as a measure of the minimum amount of sample that can be detected, is often a major concern. Sometimes these problems can be resolved by employing a fluorescence or electrochemical detector and/or preparing a derivative of the analyte. True microbore (i.e. coliunn i.d. 1.0 mm) HPLC systems can provide gains in sensitivity but these are not used extensively in forensic laboratories mainly because of practical problems associated with reproducibility and short column lifetimes. However, there is a trend towards using narrow-bore columns of 2-3 mm i.d. 

---

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... 

The first human DNA SRM developed by NIST was designed in the late 1980 s to standardize Restriction Fragment Length Polymorphism (RFLP) procedures which at that time were very new developments in the application of DNA to forensic analysis. 

Practical needs for analysis come from the activities of industrial enterprises and government functions that span manufacturing, shipping, communications, domestic power, water supplies, waste disposal, forensic analysis, environmental policies, international verification of quality and quantity (metrology), and far from least of all, national security. The need for measurements of chemicals is ubiquitous—measurements of the mass and dimensions of chemical substances and of their capacity to adsorb heat, to absorb or reflect light, and to respond to pressure and temperature. Many measurements also must be made under varying constraints of speed, cost, and location of the measurement. 

In forensic analysis, it could lead to a wrongful conviction or the guilty going unpunished. 

Forensic analysis is usually required for the collection of data in the course of determining whether legislation has been infringed. The customer requires that, above all, there is an unbroken chain of evidence from the time the samples were taken to the presentation of evidence in courts of law. In the laboratory this will include documentation and authorization for sample receipt, sample transfer, sub-sampling, laboratory notebooks, analytical procedures, calculations and observations, witness statements and sample disposal. All of these aspects can be called as evidence in court. 

Gel electrophoresis has been applied to soil DNA and RNA extracts using procedures similar to those used in DNA testing for forensic analysis. CE has also been applied to the analysis of ionic species extracted from soil. While these processes show promise for the elucidation of valuable information about soil, neither is used for common, routine soil analysis [12-14],... 

ISO has two important functions in analytical chemistry. The first is to publish descriptions of accepted methods. These are effectively industry standard methods for particular protocols. The second is in laboratory accreditation. For a laboratory to be ISO accredited, compliance with international QA standards must be confirmed by an initial assessment and subsequently from repeated audits by an independent assessor. Since ISO has no legal or regulatory powers, the standards are voluntary. It is unlikely, however, that a forensic analysis which did not conform to an ISO standard would be upheld in court, for example. Most commercial laboratories need to be accredited to remain competitive and to deal with regulatory authorities. Most university labs are not accredited, mainly due to the time and costs involved, and also to the nonroutine nature of much university research. However, university accreditation may become a requirement in the near future, especially for publicly funded research in the UK. The details of laboratory accreditation are discussed by Christie et al. (1999) and Dobb (2004). 

Tanaka E, Terada M, Nakamura T, Misawa S, Wakasugi C. 1997. Forensic analysis of eleven cyclic antidepressants in human biological samples using a new reversed-phase chromatographic column of 2 micron porous microsphe-rical silica gel. J Chromatogr B Biomed Sci Appl 692(2) 405-412. 

The main drawback of the use of color reactions for the analysis of explosives lies in their often low specificity. Although their specificity varies according to the type of reactions - and some reactions are quite specific - it is generally not safe enough to establish an identification of an explosive in a forensic laboratory on color reactions alone. When the color is obtained, the key question is whether other compounds, which are not explosives, can produce the same color under identical experimental conditions. Unfortunately, the answer is usually, yes. Thus, in forensic analysis, where an erroneous identification may lead to a gross injustice, it is generally accepted that the identification of an explosive should not depend on color reactions alone. 

Reliable identification of explosives in a modem forensic laboratory is based on instmmental techniques, mainly spectrometric, often in conjunction with chromatographic methods. Gas chromatography—mass spectrometry (GC/MS) is considered to be an excellent and reliable method in forensic analysis, including the analysis of explosives. 

Mass spectrometry has become a routine technique for forensic analysis of explosives and one of the technologies used for vapor and trace detection of hidden explosives. 

Characterization and origin identification of explosives is important in forensic analysis of post-explosion residues. In addition to the type of explosive used in a... 

J. Thomas, P. Buzzini, G. Massonnet, B. Reedy and C. Roux, Raman spectroscopy and the forensic analysis of black/grey and blue cotton fibres. Forensic Sci. Int., 152, 189-197 (2005). 

Kimura K, Nagata T, Kara K, et al. 1988. Gasoline and kerosene components in blood A forensic analysis. Hum Toxicol 7(4) 299-305. 

Forensic analysis of street drugs include that of cocaine together with excipients frequently encountered (579), amphetamines 080), and dyes found in heroin samples 081). An on-line photochemical derivitization of cannabinoids has been described 082). Other pharmaceutical agents studied in formation include nortriptyline in tablets. 083), glycyrrhizic acid from licorice extract 084, 585), pirimiphos methyl 086), digitalis glycosides 0S7), pilocarpine 088), and its antagonist atropine 009). 

Figure 3.1 A hair sample from a suspected drug user is prepared for forensic analysis. As hair grows, it incorporates small amounts of chemicals that are produced when drugs are broken down in the body. To identify these drugs, the hair is first cut into pieces and soaked in a liquid solvent The solvent removes the traces of drug metabolites from the hair so that they can be identified by chromatography and mass spectrometry.

WFLETC). From February 2002 to the present time, he has helped develop explosive analysis programs and train personnel for the Georgia Bureau of Investigation, Tucson Police Department, and the Texas Department of Public Safety. He also has provided forensic analysis in various areas for both private companies and corporations, and law enforcement agencies. 

---