ANA INS-POST LAB 4- denisse tan (1) (1)
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Centennial College *
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207
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Aerospace Engineering
Date
Dec 6, 2023
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docx
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DENISSE MAE TAN 301235992
October 9, 2023
Experiment 4:
Determination of Percentage Ethanol in Beverages by Gas
Chromatography
Observations:
The unknown sample is light brown in color and has a strong, sweet alcohol smell
The known sample has a very light brown or pale brown in color and has a strong, sweet alcohol smell.
The cuvettes/containers used to read the samples are very minute in size.
The order of analysis in the GC machine is as follows: the standard sample is run first, followed by the known sample, and finally, the unidentified sample.
Results:
Table 1: Gas Chromatography results showing Alcohol Peak, N Propanol Peak and its Average Results
Area peak
Average
sample
Alcohol
peak
1 propanol
peak
Alcohol
average
N propanol average
Standard 1
0.0218
0.1060
0.0216
0.1074
Standard 2
0.0214
0.1088
Known 1
0.0742
0.1358
0.0757
0.1566
Known 2
0.0772
0.1774
Unknown 1
0.1082
0.3119
0.0844
0.2141
Unknown 2
0.0606
0.1163
*Samples were run in duplicate and average was taken and was used for calculations
DENISSE MAE TAN 301235992
October 9, 2023
Actual results from lab manual:
DENISSE MAE TAN 301235992
October 9, 2023
POST-LAB QUESTIONS: 1. Calculate the percentage ethanol content of your known samples separately for both GCs (Show all calculations). Compare the calculated ethanol content of your known sample to the value given on its bottle. Which GC analysis gave better results? Percent Ethanol
=
0.0757
0.1566
0.0216
0.1074
x
4.75%
%
Ethanol
=
11.42%
*N propanol was used instead of acetic acid
2. Calculate the percentage ethanol content of your unknown sample separately for both GCs (Show all calculations). Are the two values similar to each other? Percent Ethanol
=
0.0844
0.2141
0.0216
0.1074
x
4.75%
%
Ethanol
=
9.31%
*N propanol was used instead of acetic acid
3. Explain why the accuracy of the internal standard method does not depend on the accuracy of the volume of sample injected into the GC?
The accuracy of the internal standard method in gas chromatography (GC) isn't tied to the exact sample injection volume. GC relies on relative ratios, comparing the area under the peaks of the compound of interest to an internal standard. Even with slight injection volume variations, both the compound and the
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