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FSC239Y5 (435)
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Lecture

FSC239 Jan 4 2011
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Department
Forensic Science
Course
FSC239Y5
Professor
Cahn
Semester
Winter

Description
FSC239 January 4 th Forensic Chemistry - application of analytical techniques to identify and compare evidence o determine composition o involves physical and chemical analyses of materials  ex. light absorption and emission - forensic labs perform analyses on wide range of materials Chemical Analyses Organic Compounds - drugs – alcohol, mj, herion - synthetic fibers - petroleum products – gas - paint binders - high grade explosives - organic compounds contain carbon - commonly bonded to H, O, Ni, S, P, Cl - nature of bonds between elements o compounds can be characterized by absorption of light - spectrophotometry: method for identifying substances based on selective absorbance of different wavelengths of light o requires material to be pure  often beyond control of FS Chromatography - separating components of a mixture based on differing attractions to a stationary phase while propelled by a moving phase - molecules having greater affinity (more soluble) for moving phase pushed along a faster rate – causes separation - can be thought of as a race btwn chemical compounds o at start, all mixed together o as race progresses, components separate o at completion, all participants separate, each cross finish line at different time - after separated, compounds are ionized and recorded on a graph - gas chromatography o liquid stationary phase and moving gas phase o gas flows through a column containing thin film of liquid  on walls – capillary, on smaller granular particles – packed o sample injected as liquid and vaporized o chromatogram generated  electrical signal given off by emerging component when ionized by detector  recorder response graphed against time  time required for a component to emerge from the column is known as the retention time o useful identifying feature but it does NOT produce specific identification o largely used to separate compounds HPLC and TLC - HPLC: high performance liquid chromatography o solid particle stationary phase and moving liquid phase – liquid pumped through column - entire process takes place at room temperature o no need to vaporize sample o useable for temperature-sensitive materials ex. explosives, LSD - TLC: solid stationary phase (coated plate) and liquid mobile phase - liquid rises up plate by
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