Gas Chromatography Formal Report - Gas Chromatography...

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Gas Chromatography Formal Report 2/28/08 Chemistry 113 section 101,
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Introduction: Gas chromatography is a, “method of separating the volatile constituents of a substance by means of gas for the purpose of analysis.” 1 It is used in science, medicine and industry for a number of purposes. The technique separates the volatile substances by pushing a vaporous mobile phase through a porous stationary phase located in a long tube. A basic gas chromatograph(GC) consists of an inert carrier gas (He, H 2 , N 2 etc.), a heated injection port, and a detector. Shown below is a basic diagram of a gas chromatograph. 2 Source: http://www.cchem.berkeley.edu/chem1b/spring04/lab_image/030.gif The two main types of gas chromatography are gas-solid chromatography and gas-liquid chromatography. The gas-liquid chromatograph is far more versatile because the stationary phase is liquid and the distribution process is partition. The gas-solid chromatograph, used in our personal GC’s, separates because the components have different adsorption affinities for the stationary phase. 2 The type of commercial gas chromatograph used in our lab was a flame ionization detector (FID). It was developed by both Harley and Pretorious, and McWilliams and Dewer. It requires three gases to operate, H 2 and O 2 for combustion, and N 2 as a carrier gas. It measures the ions produced in the flame as opposed to the heat generated by separation. 3 The FID is, “the most sensitive gas chromatographic detector for hydrocarbons such as butane or hexane. With a linear range for 6 or 7 orders of magnitude (10 6 to 10 7 ) and limits of detection in the low picogram or
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femtogram range, the FID is the most widely and successfully used gas chromatographic detector for volatile hydrocarbons and many carbon containing compounds.” 4 Both Freon 22(CHClF 2 ) and Freon 123 (C 2 HCl 2 F 3 ) fit that profile. The commercial GC uses a capillary column, a narrow long column with high efficiency ratings that is expensive to produce but worthwhile for complex samples. 2 The personal gas chromatograph we used had a Beilstein detector. Using a packed column(relatively shorter and wider than a capillary column), the GC can be created very inexpensively, using Tide detergent as the stationary phase, and methane as the carrier gas. The detector is a copper coil placed in a small frame created by the CH 4 . The active solvent in the tide is the inorganic compound Na 5 P 3 O 10 or sodium tripholyphosphate, coated with an organic surfactant. The Beilstein detector is sensitive for halogen compounds, but little else (differs from the FID). The detector emits a green-blue light when the halocarbons pass through it. 2 The term chromatography literally means color writing, and was coined by Russian chemist Mikhail Tswett in 1903 for his work on separating pigments of green leaves. In organic chemistry, the process is used to actually separate the compounds as they elute from the end of the chromatography column. Often
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This note was uploaded on 04/15/2008 for the course CHEM 113 taught by Professor Keiser,joseph during the Spring '08 term at Pennsylvania State University, University Park.

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Gas Chromatography Formal Report - Gas Chromatography...

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