[VG808]

When heavy metals “contaminate” a phyto oil, ie cotton oil, analytics testing shows a value of say nickel.

What allows for this sample to be considered homogenous enough to believe there’s no “hot spots” in the oil? 
Additionally, if the oil contains a small percentage of volatiles and 30% of other phytochemicals / constituents, what is the likelihood that the heavy metals are not homogenized?