Forensic applications detection

As the vapor leaves the tube, the compounds in the sample are detected by a device such as a thermal conductivity detector. This instrument continuously measures the thermal conductivity (the ability to conduct heat) of the carrier gas, which changes when a solute is present. The detection techniques are very sensitive, allowing tiny amounts of solutes to be detected. Many environmental monitoring and forensic applications have been developed. 

HPLC has had considerable success in separating compounds as diverse as steroids, carbohydrates, vitamins, dyestuffs, pesticides and polymers. It is used routinely for the assay of pharmaceutical products, the monitoring of drugs and metabolites in body fluids and for other biomedical, biochemical and forensic applications, such as the detection of drugs of abuse. The determination of additives in foodstuffs and beverages including sugars,... 

Multitarget forensic applications of HPLC for other drug classes are also available in the literature. Josefsson et al. [77] applied HPLC-MS-MS to the determination of 19 neuroleptics and their major metabolites in human tissues and body fluids. Optimal separation was achieved using a cyano column within a 9 min gradient run. Detection was curried out in SRM reaching LQDs down to the lower ng/mL level, although more than a 10-fold difference in signal response was observed between analytes. The method was subjected to partial validation only. 

The FAAS method offers similar detection limits to NAA and is suitable for the determination of low levels of lead. Equipment costs are reasonable and the instrumentation is commonplace in many analytical laboratories. A large number of metallic elements, over a wide concentration range, extending down to ultra-trace level, can be analyzed, thus making the technique versatile and useful for other forensic applications as well as FDR detection. Apart from cost, the main advantages are simplicity, speed of analysis, and in house operation. One disadvantage of FAAS is that it is not capable of simultaneous multielement analysis. 

Several HPLC oxidative electrochemical methods have been developed for the analyses of drugs and metabolites in body fluids and the quantitative analysis of morphine was one of the first forensic applications of this detection technique. By applying a potential of +0.6V (versus an Ag/ AgCl reference electrode) the presence of morphine can be confirmed in whole blood and a detection level of 10 ng ml for a 100-pl sample can be achieved routinely. 

Until recently, DNA quantification in forensic analyses has most commonly involved the use of slot-blot methods. In the past few years, the forensics community has shifted focus to the use of quantitative PCR as the preferred method for quantification. Both methods allow for human-specific DNA quantification, although qPCR has significantly lower limits of detection and gives an indication of the PCR-amplifiability of the DNA as well. Recently, multiplex qPCR assays have been developed to simultaneously determine the total amount of genomic and mitochondrial DNA, total genomic and male DNA, or assess the extent of DNA degradation for specific forensic applications. Because of the utility of qPCR to the forensic community, we focus on the development of qPCR on microdevices here. 

In Chapter 5, we look at modes of detection, again examining those that we feel are best suited to forensic applications. 

F. Bami, S.W. Lewis, A. Berti, G.M. Miskelly, and G. Lago, Forensic application of the luminol reaction as a presumptive test for latent blood detection, Talanta 72 (2007), pp. 896-913. 

Inoue H, Maeno Y, Iwasa M, et al. (1997) Sensitive detection of human globin chains by microbore high-performance liquid chromatography and its forensic applications. Journal of Chromatography B, Biomedical Sciences Applications 688 221-227. 

J.B.F. Lloyd and D.A. Parry, Forensic applications of the determination of benzodiazepines in blood samples by microcolumn cleanup and high-performance liquid chromatography with reductive mode electrochemical detection, J. Anal Toxicol, 1989, 13, 163-168. 

Particles located by ET analysis can be treated in similar fashion, based on the tracks and craters found on the film they can either be manipulated individually or the whole film transferred to SIMS or LA-ICPMS analysis (Figure 5.11). The combination of FT-TIMS is considered one of the most sensitive (FT) and accurate (multicollector TIMS) techniques for detection and isotopic characterization of uranium particles for nuclear forensic applications. 

Ion mobility spectrometry (IMS, Section 5.5) is the most common instrument used in tiie field detection of explosives. At airports, IMS is utili2fid to screen devices such as portable computers a swiped sample obtained by wiping a sample pad over the case is inserted into the instrument, producing an alarm-noalarm response. IMS can also be used in a laboratory as part of a GQMS or IMS-MS system, but to date its forensic applications have been outside the laboratory. IMS is also used at border crossings and ports to detect smu led drugs. 

Xe atoms. Incredibly, it is suggested that this technology may be combined with nanofluidics for the genetic analysis of the DNA present within a single cell In comparison, current methods utilize PCR amplification, whereby small samples of DNA are repeatedly replicated in order to facilitate detection. Such analyses will be of use for the detection of genetic markers for cancer or other diseases such as HIV. The ability to identify proteins will be essential for fumre diagnostic and forensics applications. 

The main advantage of using the near-infrared system for forensic science detection is reduced fluorescence, which can be a major problem with a sample in a matrix however the simpler, more flexible optics of the visible system can make this the system of choice in many applications. The examples given in the chapter could be accomplished with either system, depending on the level of background fluorescence and on the sensitivity required. Near-infrared systems do require considerably higher laser powers to obtain equivalent spectra. 

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