BV Laboratories - Montreal, is accredited by the SCC for the F2-F4 analysis and by the CEAEQ for the Petroleum Hydrocarbons C10 to C50.
No comparative study has been done for these analyses because they answer two different regulations: Federal for the F2-F4 fractions and Québec Provincial for the C10-C50 fraction.
There are a few major differences between both methods that could explain in part potential differences in results.
First, the hexane extract for F2-F4 is combined with dichloromethane (DCM) for the silica gel treatment in order to retain polar compounds that are not considered as being part of petroleum hydrocarbons whereas the C10-C50 hexane extract is treated as is with silica gel. Since DCM is a polar solvent and hexane is non-polar solvent, this means that the F2-F4 silica gel treated extract could contain more polar compounds compared to the C10-C50 extract.
Secondly, the standards used for the instrument calibration are different. F2-F4 uses n-alkanes C10, C16, C34 and C50 when C10-C50 uses a diesel standard.
A comparative study could not give an exact % difference between the two methods that could be applied as a general rule for all samples because it could vary based on many factors like the type of contaminant e.g. light distillate versus heavier distillate and the nature of the sample like the biogenic content of a soil for example.
So if both Provincial and Federal regulations have to be followed for a specific site, both tests have to be performed in order to compare results to the right regulation.