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NAME THAT SUBSTANCE MDMAHeroin CocaineMeth MDMA heroin cocaine Baking soda and powder

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Chromatography Separation of Mixtures

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What Is Chromatography? A family of laboratory techniques for separating mixtures into their component compounds Uses some version of a technique in which two phases, one mobile, one stationary, flow past one another The mixture separates as it interacts with the two phases

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Basic Principle Different compounds will stick to a solid surface with different degrees of strength or vary in the efficiency with which they dissolve in a liquid

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Basic Principles A mobile phase sweeps the sample over a stationary phase like the wind sweeps the swarm over the flower bed

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Basic Principles When a mixture of compounds flows over a surface, the molecules will stick to the surface If a molecule does not stick to the surface too strongly, the molecule stick & unstick many times as it is swept along the surface Over time, the molecules will become physically separated from each other

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Basic Principles When the molecules reach the far end of the surface, they are detected or measured one at a time as they emerge Chromatography is non-destructive does not alter the molecular structure of the compounds

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Types of Chromatographic Attraction Adsorption Chromatography depends on physical forces such as dipole attraction to cause the molecules to stick to the stationary phase column, TLC, HPLC

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Types of Chromatographic Attraction Partition Chromatography depends on the relative solubility of the mixtures molecules in the stationary phase coating polarity may also have some effect gas chromatography

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Types of Chromatographic Attraction Size-exclusion the relative sizes of the molecules determine how fast the molecules move through the stationary phase large molecules flow right through small molecules spend time trapped in the pores of the stationary phase gel filtration chromatography

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Types of Chromatographic Attraction Ion-exchange depends on the relative strength with which ions interact with an ionic resin less strongly held ions are displaced by more strongly attaching ions one kind of ion is exchanged for another ion exchange chromatography

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Gas Chromatography Stationary phase a solid or very syrupy liquid lines a tube (column) silicone polymers (like Silly Putty) commonly used Mobile phase an inert gas nitrogen helium

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Gas Chromatograph (GC)

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GC Columns A packed column A capillary column

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Schematic of a GC

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Retention Time

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The time between when the sample is injected & when it exits the column reaching the detector Tm is the time taken for the mobile phase to pass through the column

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Analysis Using the GC Retention time can be used as an identifying characteristic of a substance retention times may not be unique GC is not an absolute method of identification An extremely sensitive technique area under a peak is proportional to the quantity of substance present allows quantitation of sample

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Identification of Accelerants unevaporated gasoline 90% evaporated gasoline unevaporated kerosene 90% evaporated kerosene

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Pyrolysis Gas Chromatography Used when sample does not readily dissolve in a solvent If heating such sample at high temp (500- 1000 0 C) decomposes it into gaseous products, the products can be analyzed by CGC A pyrogram is obtained

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Next Step? Now that you know WHAT is in there (qualitative), what do you want to know next?

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Mass Spectrometer (MS)

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Mass Spectrometer

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Mass Spectrum