Lab6-GC-LC

Lab6-GC-LC - Chemistry 227 Fall 2009 Lab 6: Chromatography...

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Chemistry 227 – Fall 2009 Lab 6: Chromatography Overview: Chromatography is one of the most widely used methods for chemical separation. In this lab, you will learn about the principles of chromatography, primarily through experiments with gas chromatography (GC), but you will also have a brief experience with high performance liquid chromatography (HPLC). You will explore the role of stationary phase in separation and the factors affecting resolution, use the Kovats index to aid in qualitative identification of compounds, and make a quantitative determination on a sample by standard addition. In addition, you will see how to manipulate mobile phase and detection to improve HPLC separations. Safety Use care when handling organic compounds in this lab. Do not leave containers open, do not take large quantities of any solvent or mixture, and use care not to spill substances on yourself, on any equipment, or on the computer. Use caution when you handle the syringe and make injections; the needle is sharp and the injection and exit ports of the GC are hot. Dispose of excess reagents in the appropriate container. Be sure that vials containing samples and solvents are kept tightly closed when not in use. Collecting Data The gas chromatographs should be ready to operate when you arrive in the lab, except for final adjustments of the column flow rate and the detector bridge current. About 4 hours are required for the GCs to stabilize at the operating temperature, so don’t adjust the temperature settings without first consulting a lab instructor. Begin this experiment by locating the various controls and ports on the GC; these are the current/temperature meter, meter selector switch, injection ports for columns A and B, flow adjustment controls for columns A and B, exit ports on the left side of instrument, detector power switch, detector polarity switch, detector bridge current control, attenuator selector switch, zero adjustment control, and temperature controls for the injector ports, detector, and columns. Do not adjust any controls until the instructor or a lab assistant has reviewed the GC operation procedures with you and answered your questions. However, you may use the meter selector switch to check temperatures and the detector bridge current. The following control settings are the target for this experiment: column temperature — 110 ºC detector temperature — 130 ºC injector temperature — 130–135 ºC detector bridge current — set to its maximum (should be at least 225 mA) Adjust the attenuator so that the peaks for eluting compounds are on-scale (i.e., between ±50 mV; peaks are larger when the attenuator setting is smaller). Start with the attenuation settings, injection volumes, and flow rates suggested in Table I below, and then make adjustments as necessary. When the polarity switch is in the + position, positive peaks will be seen for injections on column A, and negative peaks, for injections on column B. The detector output zero
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This note was uploaded on 03/15/2012 for the course CHEM 227 taught by Professor Stevengoates during the Fall '10 term at BYU.

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Lab6-GC-LC - Chemistry 227 Fall 2009 Lab 6: Chromatography...

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