CHE 107 Lecture Notes - Lecture 39: Spectrophotometry

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Types of fibers, natural: derived in whole from animal/plant sources. Cotton: man-made, regenerated: manufactured from natural raw materials. Triacetate: synthetic: produced solely from synthetic chemicals. Polymers/macromolecules: a large # of atoms arranged in repeating units known as monomers: fiber evidence: Quality of fiber evidence depends on ability of criminalist to: identify origin of fiber, be able to narrow possibilities to a limited # of sources. If examiner is presented w/ fabrics that can be exactly fitted together at torn edges, it"s a virtual certainty that fabrics were of common origin. Presence of delustering particles that reduce shine. Cross-sectional shape of fiber: methods for fiber comparison: Infrared spectrophotometry: rapid & reliable method for identifying generic class of fibers: molecules that compose manufactured fiber selectively absorb infrared light to form characteristic pattern. Microspectrophotometer: combo of traditional light microscope & spectrophotometer: allows forensic analyst to view object under microscope while simultaneously obtaining its visible of infrared absorption pattern.

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