NATS 1575 Study Guide - Final Guide: Neutron Activation Analysis, Gunshot Residue, Restriction Fragment Length Polymorphism
30 Aug 2016
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Document Summary
Can be used to simultaneously observe a specimen (microscope aspect) while obtaining its absorption spectrum (spectrophotometer aspect: uv and ir spectra are the most commonly analyzed. Extremely valuable when observing trace evidence which a normal spectrophotometer cannot do. Spectrophotometers help characterize substances based on how much em radiation they absorb. The quantity of light absorbed at any frequency is directly proportional to the concentration of the absorbing species: this is known as beer"s law. Absorbance is proportional to (molar absorptivity constant)(concentration of substance)(path length of the substance) Different materials always have distinctively different absorption spectra; each spectrum is therefore equivalent to a fingerprint of that substance. Gas chromatography separates specimens into its individual components and tentatively identifies them: stationary phase = a liquid. E. g. chloroform or pentane: mobile phase = an inert gas. Gc/ms is useful in the analysis of drugs, flammable residues, and gunshot residues. Separates and identifies highly complex mixtures into their components very quickly.
