Things are still going well and I have run a full set of my 11 canisters. The system is working well and I have done a little bit of fine tuninig in order to maximise the sensitivity for the compounds that I am interested in. These compounds, which correspond to my compounds detected in the snow samples (determined with SPME) are rather heavy (C2-C8).
I have, therefore, removed the water trap (cooled by dry ice) on the preconcentration system to avoid trapping my analytes there (this is less of a problem with more volatile compounds). I am using an HP-5 column, which is not sensitive to water as the previously used PLOT column for light hydrocarbons (which I would like to determine at a later date). I also heat out the liquid nitrogen trap under vacuum before proceeding to the next sample in order to avoid residues being stuck in the trap. Blank runs show that this is working well.
I also use 30% more sample for analysis than the people ususally using the system, because my peaks are quite small. The additional amount of sample and resulting increased sensitivity are much more reliable with an improved signal-to-noise ratio.