The Chemistry 105 Gas Chromatography Report

Spring 2009

 

This lab report is scored 50 points for your value and 50 points for your report.

 

Team members cooperate on preparing the two sets of standards and running them on the instrument and sharing the standard results. Each person runs their own unknown. The report, including spreadsheet workup of the standards and unknown, must be the sole work of the person submitting the report. List the names of all the team members as an Acknowledgement.

 

The report is to be handed in on separate paper, and must include the following:

 

Experimental Section: (10 points)

 

Using tables whenever possible and brief narratives whenever necessary, describe the equipment you used, including the make and model of the gas chromatograph, the kind of detector it was equipped with, and the make, model and description of the column you used (this will be on its tag). Also give the make, model and size of the syringe used for sample injection. Give the make and model of the readout device, and describe what it did. List the type and purity of the gas used.

 

List all the operating parameters of your gas chromatograph, including gas flow rates, operating temperatures for all its parts that you can set, and any other settings that will affect the output of this instrument.

 

Give the manufacturer or source and purity of any reagent you used.

 

Describe how your samples were prepared and run. Acknowledge all the team members and what part each played in the preparation of the standards. Remember there must be at least two sets of standards for each team.

 

Data and Results: (20 points)

 

Include enough samples of your chromatograms to support any arguments you make about peak identification, peak resolution, quality of peaks and peak area.

 

Using Excel, prepare your working curves using the internal standard method with methanol as the internal standard. Plot out these curves and do a standard Linear Least Squares analysis, including Sc, if the data are linear. If they are not linear, do a non-linear fit and estimate the errors.

 

Summarize all results in easy to read tables that will be used to support your arguments about the quality of your analysis, and why we should believe the %(v/v) Ethanol value plus or minus your error that you produce. Remember, after all the working curves and statistical analysis, you must come up with one number and error to report.

 

Defense of Results (AKA “The Conclusion”) (20 points)

 

Here is where you put everything together. Explain how and why the calculations were done using an internal standard. Explain why the data are good, and believable, or why other data were excluded because they were not. Be sure to refer to samples of your chromatograms, as well as your graphs and results when doing this. Explain how the final reported value and error was determined. Finally, summarize why the final number and error you are reporting is the best possible number for this experiment. Include any improvements you would make, knowing what you know now.

 

Reported Value (50 points)

 

You will be allowed the usual 2.0% uncertainty we have used for the other instrumental methods in this course when the instructor grades your reported result. Report %(v/v) Ethanol +or- the absolute error in the same units.