(AOM) Analysis of Organic Materials Module Overview

Analysis of Organic Materials Module Overview

Forensic scientists have multiple tools at their disposal. The key is to know which piece of equipment is the right one for the job. A basic knowledge of chemistry and physics can help forensic scientists determine which tools to use. With proper training and technique, crime labs incorporate the use of chromatography and spectrophotometry to effectively fight crime and solve mysteries.

Essential Questions

  1. How are organic materials of evidence analyzed?
  2. What are the various types of chromatography and why are they so important to the field of Forensics?
  3. How can Spectrophotometry be used to identify unknown samples?
  4. What evidence can be detected with Mass Spectrometry?

Key Terms

  1. Organic - All organic materials contain carbon and are generally living things or derived from living things.
  2. Inorganic - Materials that do not contain Carbon.
  3. Qualitative -Pertains to the properties or qualities of the material, such as color or opacity.
  4. Quantitative - Pertains to the number or percent composition of the material. Capability of being measured, such as boiling point, temperature.
  5. Chromatography - A technique used to separate the components of a chemical mixture by moving the mixture along a stationary material, such as gelatin. Different components of the mixture are caught by the material at different rates and form isolated bands that can then be analyzed.
  6. Gas Chromatography - A technique for analyzing a mixture of volatile substances in which the mixture is carried by an inert gas through a column packed with a selective adsorbent and a detector records on a moving strip the conductivity of the gas leaving the tube. Peaks on the resulting graph indicate the presence of a particular component.
  7. Thin-Layer Chromatography - A form of chromatography in which components of a liquid mixture are separated by means of a thin layer of adsorbent material coated on a glass, plastic, or foil sheet.
  8. Column Chromatography - Chromatography that uses selective adsorption by a column of powders.
  9. Adsorption - The process by which molecules of a substance, such as a gas or a liquid, collect on the surface of another substance, such as a solid. The molecules are attracted to the surface, but do not enter the solid's minute spaces as in absorption.
  10. Electrophoresis - A method of separating substances, especially proteins, and analyzing molecular structure based on the rate of movement of each component in a colloidal suspension while under the influence of an electric field.
  11. High Pressure Liquid Chromatography - A form of column chromatography used frequently in biochemistry and analytical chemistry to separate, identify, and quantify compounds. HPLC utilizes a column that holds chromatographic packing material (stationary phase), a pump that moves the mobile phase(s) through the column, and a detector that shows the retention times of the molecules. Retention time varies depending on the interactions between the stationary phase, molecules being analyzed, and the solvent(s) used.
  12. Solvent - A substance, usually a liquid, that dissolves or is capable of dissolving.
  13. Solute - The substance dissolved in solvent to form a solution.
  14. Solution - A homogeneous mixture of one or more substances (solutes) dispersed molecularly in a sufficient quantity of dissolving medium (solvent).
  15. Retention Factor (Rf Factor) - Quantitative indication of how far a compound travels in a particular solvent good indicator of whether an unknown and a known compound are similar, if not identical.
  16. Spectrophotometry - The study of the absorption of light by chemical substances. A spectrophotometer is an instrument used to measure and record the absorption spectrum of a chemical substance.
  17. Mass Spectrophotometry - A compound is bombarded with a stream of electrons where the compound breaks into fragments. Each compound gives a unique set of fragments which can be thought of as that compound's "fingerprint".

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