Gas Chromatography Reports

There are two separate GC reports from two different experiments: the results from the GC analysis of the alkyl acetates unknown mixture and the results from the GC analysis of the ethyl and butyl acetate unknown mixture and the distillation fractions saved from the Distillation Experiment.

Gas Chromatography Report -- Alkyl Acetates Unknown

The report consists of three parts: 1) the Report Form; 2) the chromatograms with calculations; and 3) a written summary of results.

1) Fill in the required information on the report form. The form should be self-explanatory.

2) Make a photocopy of your chromatograms (if it is not already a photocopy) with only one chromatogram per page. Use a blue or green pen to mark on the photocopied chromatograms (do not use a pencil or red or black ink!).

Identify each peak in every chromatogram. Using a straight-edge, clearly draw the baselines for the peaks on each of your chromatograms (depending on the recorder, it may already be drawn). Mark where you will make measurements for the retention times (if necessary) and peak heights and widths. Each retention time should be marked exactly as it appears in the lab textbook (if it is not already printed on the chromatogram). The calculation of each peak area should appear on the chromatogram exactly as it appears in the textbook. Use mm for your measurement units and measure +/- 0.5 mm. The calculation of the mole percent composition of the unknown sample should be shown in the white space on the photocopied chromatogram just as it appears in the textbook. Calculate the mole %'s to 2 significant figures.

Paste your original chromatograms in your notebook.

3) The written summary of results should include these sections, appropriately titled:

- an Introduction about the goal and procedure of the GC experiment; include a paragraph on the basic construction and operation of a gas chromatograph;

- a description of the Data you obtained and how you manipulated it (e.g. calculation of peak areas) (do not reproduce all the data itself here);

- an Analysis of the data (e.g. identification of the peaks in the standard mixture and in the unknown mixture chromatograms; determination of the mole %'s of the unknown components);

- a Discussion/Conclusion about the composition of your unknown, taking into account the textbook discussion of response factors in the quantitative analysis section (but which you did not do).

The summary should be typed. Please use 1-inch margins, 12-pt font, and double-spaced, printed on only one side of the page.

Assemble the report in this order:

  • Report Form
  • chromatograms with calculations
  • other calculations
  • written summary

You will be graded on your adherence to these instructions.

 

Gas Chromatography Report -- Distillation Unknown

The report consists of three main parts: 1) the Report Form, 2) the chromatograms, and 3) a written summary of results.

1) Fill in the required information on the Report Form. The form should be self-explanatory.

2) The chromatograms should be in the order: unknown A or B, three distillate fractions in ascending temperature order. See the instructions above for photocopying and marking the chromatograms. Each chromatogram should include the area and percent calculations exactly as those calculations appear in the textbook. Any other calculations should be on a separate page. Use mm for your measurement units and measure +/- 0.5 mm. Calculate the mole %'s to 2 significant figures.

3) The written summary of results should include these sections, appropriately titled:

- an Introduction about the goal and procedure of the GC experiment (ideally, as the experiment was designed to follow-up the Distillation Experiment); [Note for Fall, 2017: Briefly explain how the actual experiment deviated from the the planned experiment.]l
- a description of the Data you obtained and how you manipulated it (e.g. calculation of the peak areas - but do not reproduce the raw data here);

- an Analysis of the data that would include the mole %'s as calculated on the chromatograms;

- a Discussion/Conclusion. The conclusion should consist of three parts:

a) the determination of the mole % composition of your distillate unknown A or B from this GC experiment; and

b) a comparison of the determination of mole % composition by fractional column distillation (presumably the most efficient distillation you performed -- efficiency is measured by separation of components, not percent recovery) and by GC (make an explicit comparison between the appearance of the graph from the fractional column distillation and the GC chromatogram of the unknown); and

c) a discussion of the three distillate fractions you saved with respect to their presumed composition when you saved them compared to the actual composition as determined by GC. On the graphs you saved from the distillation experiment, explicitly mark the three fractions you saved.

Be sure you restate your assumptions and conclusions from the distillation as you discuss them since I won't have a copy of your report (except for the bar graphs). If you made serious errors in your assumptions from the distillation experiment, you should correct them for this report.

This is not the place to discuss GC theory or to explain the procedure. If something went wrong with your experiment and you lack good data, this is the place to briefly explain it. A knowledgeable reader who had not done the experiment should have a good idea of what you did and what you found out by reading your summary.Please do not labor long and hard over discussing these results, but do attempt to make the correlation between your distillation and chromatography results.

The summary should be typed. Please use 1-inch margins, 12-pt font, and double-spaced, printed on only one side of the page.

Assemble the report in this order

  • Report Form
  • chromatograms with calculations
  • other calculations
  • copies of distillation graphs, summary

You will be graded on your adherence to these instructions.