Method 1:
1. Add 9.5 mL of Methanol to each flask
2. Now add the following amounts of toluene (Concentration 1000mg L-1) to each flask
- Flask 1 - 100µL (Toluene)
- Flask 2 - 80µL (Toluene)
- Flask 3 - 60µL (Toluene)
- Flask 4 - 40µL (Toluene)
- Flask 5 - 20µL (Toluene)
3. Make each flask up to the mark (10mL) with methanol
4. Put stoppers into the necks of the flasks and mix by inverting them 6 times
5. Inject 1µL of solution into the chromatograph and record the peak area
6. Repeat this process for all 5 flasks and record the results accordingly
7. Now run the unknown sample through the chromatograph once.
Results for method 1
|
Flask No.
|
Volume of Toluene added / mL
|
Peak Area of Toluene
|
Toluene Concentration mg L-1
|
|
1
|
100
|
59.6229
|
10
|
|
2
|
80
|
53.9481
|
8
|
|
3
|
60
|
44.7381
|
6
|
|
4
|
40
|
26.5328
|
4
|
|
5
|
20
|
12.7134
|
2
|
|
Unknown
|
|
32.5719
|
4.8553
|
Method 2 - Using internal standard (Ethylbenzene)
1. Add 100µL Ethyl benzene (Concentration 1000mg L-1) to each flask & mix thoroughly
2. Run each solution through the chromatograph as (Method 1 Step 5) & record the results.
3. Now add 100µL ethyl benzene to the unknown, mix, inject and record the result.
4. Choose anyone of the standards & inject it a further 4 times & record the results
Results for method 2 (Steps 1 to 3)
|
Flask No.
|
Area of Toluene
|
Area of Ethylbenzene
|
Area of Toluene
Area of Ethylbenzene
|
|
1
|
65.6147
|
45.3774
|
1.4460
|
|
2
|
53.7759
|
71.4809
|
0.7523
|
|
3
|
38.3167
|
72.7725
|
0.5265
|
|
4
|
27.0729
|
75.4286
|
0.3589
|
|
5
|
12.5096
|
52.0932
|
0.2401
|
|
Unknown
|
34.1252
|
36.0508
|
0.9466
|
Results for method 2 (Step4 the repeated sample)
|
Sample (A, B or C)
|
Retention Time / min
|
Peak Area
|
|
|
1
|
3.000
|
68.6642
|
|
2
|
2.992
|
45.6637
|
|
3
|
2.992
|
45.6637
|
|
4
|
3.000
|
75.1459
|
|
5
|
3.092
|
41.9748
|
|
Mean value
|
|
55.4225
|
Questions to be answered
1. Using Excel, construct a calibration graph of concentration vsarea ratio for your results from Method 2, print it off and calculate the concentration in mg L-1 of toluene in the unknown sample.
2. Using both the Toluene concentrations for the unknown sample. Calculate the Average concentration of Toluene using the table below
|
|
Toluene Concentration
mg L-1
|
|
Method 1
|
4.8553
|
|
Method 2
|
|
|
Average concentration
|
|