What causes differences in limits of detection?

I'm wondering what causes the limits of detection (LOD) to vary between different compounds, when calculated from the data obtained from one sample.


I've analyzed a 0,1 µg/ml sample, containing fluorene, fluoranthene and benzo[*a*]pyrene in toluene, using GC-MS. I calculated the LODs to be 0,04 µg/ml, 0,02 µg/ml and 0,03 µg/ml. What could be the reason for the differences between the values?


