{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

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

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
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 adjustment control can be set so that the baseline is near zero, but this is not a critical factor as long as all signals during a separation run are within the range of ± 50 mV.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern