Distinguishing between cellular and Fe-oxide-associated trace elements in phytoplankton

In cultures and in nature, ferric (oxyhydro-)oxides (FeO_x) precipitate and become associated with phytoplankton surfaces. Other trace elements adsorb on FeO_x and it is thus difficult to differentiate between cellular- and oxide-associated concentrations of both iron and these elements. Existing techniques to selectively dissolve the FeO_x associated with phytoplankton surfaces often contaminate the sample or necessitate elaborate pre-cleaning procedures and/or proceed by unknown and thus uncontrolled mechanisms.