587 08 wk02 ch26_27 GC std 2pg

587 08 wk02 ch26_27 GC std 2pg - 1 Chromatographic...

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Unformatted text preview: 1 Chromatographic Separations & Gas Chromatography Chapters 26 & 27 Typical GC Instrumentation • temperature controlled oven • GC column – with connections to gas & sample injection ports, • detection port – with selected detectors attached Chromatographic Separation Methods = . Question : What information do we obtain from a GC analysis? Commonly, the GC system is coupled and sold with software and automatic Injectors. Answer: It depends on the GC components, 2 Example • This GC separation used – column = 15 foot Carbosphere capillary (1/16 th inch) • The column is always heated in the oven, and the temperature is typically listed in the specs. • In this example, the column was heated to 225 ◦ C – TCD detector = Thermal Conductivity Detector Q: How do we know that peak #3 is Methane, and how do we know that it is 1% of the mixture? Another Example • In this example, – methane emerges from the column at 6 minutes after entering the column – as compared to ~4.5 in the last GC chromatogram • Note that the column type is different – And • In addition, the Flow Rate of the carrier gas (helium) has also changed from 15 ml/min to 65 ml/min 3 Chromatography • Mobile Phase – either gas, liquid, or supercritical fluid – transports • Stationary Phase – exists within – is an immiscible ‘substance’ (phase) – adsorbs/absorbs and desorbs sample components at different rates – well-characterized for specific chemical types • Planar Chromatography – stationary phase is supported on a flat plate – • Column Chromatography – stationary phase is secured in a column (tube) – mobile phase is forced through via pressure – Classifications of column chromatography • Liquid Chromatography • Gas Chromatography • Supercritical Fluid Chromatography 4 Column Chromatography Classification: Obtaining the Chromatogram – – a series of peaks is obtained – the position of peaks determines the component after comparison to a calibration standard chromatogram – the areas under the peaks are a quantitative measure of the component’s relative concentration 5 Zone Broadening...
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This note was uploaded on 07/17/2008 for the course CHEM 587 taught by Professor Allen during the Spring '08 term at Ohio State.

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587 08 wk02 ch26_27 GC std 2pg - 1 Chromatographic...

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