Since neither filtration nor centrifuging appear always to separate the non-bioavailable fraction of the test substance from that which is bioavailable (especially for super-lipophilic chemicals, i.e. those chemicals with a log Pow > 5) (1) (5), samples may not be subjected to those treatments.
Glede na to, da ne filtriranje ne centrifugiranje vedno ne ločita delcev preskusne snovi, ki niso biološko dostopni, od tistih, ki so biouporabni (zlasti za superlipofilne kemikalije, tj. kemikalije z log Pow > 5) (1) (5), vzorci ne smejo biti izpostavljeni takemu ravnanju.