A CRITICAL EVALUATION OF INFRARED ANALYSIS AND MASS SPECTROMETRY IN FORENSIC SCIENCE : ESSAY
The outline
Introductionof Infrared Analysisof Mass Spectrometryof the uses in forensic analysiscomparison of Infrared Analysis and Mass SpectrometryCited
Introduction
order to answer the variety of questions that is posed to the forensic investigation, it is frequently necessary to conduct studies of individual objects using methods that require deep knowledge not only in the field of forensic medicine, but sciences , including criminology. The objects of such studies are the victims, defendants, suspects, weapon injuries and fabric body, clothing, footwear, materials of criminal cases and others. Amongst the several instruments that forensic scientists use in their day-to-day use, in order to aid investigators to determine how a crime was committed, both the infrared spectrophotometer and the mass spectrometer are on top of the list. These instruments are routinely used in molecular analysis and for the determinations of chemical structures (Siegel, Saukko, & Knupfer, 2000). The methods have different value and background; however have the same power and effect in investigations. The methods provide investigation with the quick and reliable results of evidence, contributing to a rapid and successful disclosure of crime. Identification and comparison of the materials is carried out by means of spectral libraries. p align="justify"> of Infrared Analysis
spectroscopy (IR) or Infrared Analysis is the section of the spectroscopy covering longer wavelengths (> 730 nm for visible light, a red border). Infrared spectra arise from the vibration (rotational part) of the molecules, namely - as a result of transitions between the vibration levels of the ground electronic state of molecules. IR radiation absorbs many gases, except O2, N2, H2, Cl2 and monatomic gases. Absorption occurs at a wavelength, which is characteristic for each specific gas, for CO, for example, the wavelength is 4.7 microns (P. & P. ​​Atkins, 2009). With the help of infrared absorption spectra it can be set different molecular structure of organic (and inorganic) substances with relatively short molecules: antibiotics, enzymes, alkaloids, polymers, complex compounds. The vibration spectra of molecules of various organic (and inorganic) substances with a relatively long molecules (proteins, fats, carbohydrates, DNA, RNA, etc.) Are in the terahertz range, so the structure of these molecules can be installed using radio frequency terahertz spectrometer (Mukamel, 2000). The number and position of the peaks in the IR absorption spectra can be judged from the nature of the substance (qualitative analysis), and the intensity of the absorption bands - the number of substances (quantitative analysis)., IR spectroscopy is based on the fact that irradiation of a substance is non-monochromatic infrared exists because of the vibration and electronic degrees of freedom, that is due to the absorbed incident radiation, at frequencies corresponding to the energy that appears because of the difference of the vibration and electronic levels. In the transmission spectrum appear the features that allow to judge the characteristic frequencies of molecular vibrations and their electronic properties. Spectral characteristics (position of the maxima of bands and their half-width, intensity) depend on the masses of its constituent material atoms, the geometrical structure, the characteristics of interatomic forces, the charge distribution (Hamm, Lim, Hochstrasser, 1998).
of Mass Spectrometry
spectrometry is one of the most effective methods for expressing the analysis and establishing a structure of individual organic, synthetic and natural compounds and their mixtures (Price & Phil 1991). Due to its extremely high sensitivity and the possibility of using in combination with gas and liquid chromatography, this method is widely used in organic, bioorganic, biological, physical, analytical, medical chemistry, the chemistry, pharmacology, toxicology, environmental protection, forensic and in control of production. One way to establish the structure of the investigated compounds by this method is automatically registered spectrum of the comparison spectra with the bank of spectra that are entered into the computer memory. Mass spectroscopy is a method based on the research of materials by determining the mass of ions of the substance (often related to their mass ion charge) and their quantities (Fenn, Mann, Meng, Wong, Whitehouse, 1989). The sequence of values ​​?? of t...
