1. The fibre (100?m Poly Dimethyl Siloxane (PDMS) was conditioned in the GC injector port for about 2-3 minutes at 250?C to remove any contaminants before extraction started.

2. First sample was unleaded petrol, put in a vial at 50?C and heated constantly while the fibre was exposed to the headspace of the vial for 20 minutes.

3. The fibre was withdraw into the needle and was pulled out carefully from the sample vial and immediately injected into the GC-MS with desorption time of 80 seconds.

4. After 80 seconds pull out the fibre first slowly before taken out the needle holder from the injection and wait 16 minutes for the detector to analyse the sample.

5. The extraction was stopped at given time and prep run and change the folder name to the next sample and go to prep run modes to clean the SPME fibre about 2-3 minutes.

6. While waiting, by using the mass spectra library, the major compounds (4 spots) in in the sample were identified.

7. Step 2 – 6 were repeated using diesel run for (20 minutes), paint thinner was run for (10 minutes) and unknown run for (26 minutes).