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

 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)

Results for method 2 (Step4 the repeated sample)

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