I have conducted some standard runs in the past weeks and set up 13 calibration curves for aromatic species. These include toluene, benzene, benzaldehyde and several others. I have also removed the water as described below and achieved some very good results.
My sensitivity has increased by about 2 orders of magnitude – my smallest standard used to be 1.25 ug/L, now it is 0.01 ug/L and I think that I can still go lower for most of the species. The reason is the reduced amount of water that enters the system, giving me a better gain on the splitless injection, which loads all of my analytes on the column. I have not calculated an LOD yet, because I need more replicates for that, but it will improve drastically.
My first calibration line covers a concentration range from 0.01 – 1000 ug/L with decent linearity. However, with increasing concentration I have observed saturation of fiber, i.e. the loading capacity has been reached, leading to a plateau at high concentrations, suggesting a curvilinear calibration line.
As a consequence I will set up different calibration lines for several concentration ranges and add more standards. I will also consider diluting highly concentrated samples, should this be necessary. From what I have seen so far, this should not be necessary, because observed concentrations were considerably lower than last year.
