3. Results and discussion
3.1. Gas chromatography (GC) separation
Since hydrocarbons C6–C20 are apolar compounds columns with apolar properties were selected for this study. In order to achieve separation of all analytes and appropriate peak shapes a temperature program was optimized. Firstly, an experiment with a constant increasing of temperature was performed in order to obtain the retention times of analytes, and then introduced three different temperature ramps in order to achieved full separation of analytes. Unfortunately, no separation of p-xylene andm-xylene was achieved. Both compounds were eluted from the column at the same time. This is caused by these analytes having a similar boiling point. However, separation from o-xylene was achieved successfully. Therefore, in further analysis both p-xylene and
m-xylene compounds were treated as one analyte p-(m)-xylene. The flow rate of carrier gas was also optimized. Conditions of 1, 2 and 4 mL min−1 were tested and a flow rate of 1 mL min−1 gave the best results.