Evaluation of cations and chelating agents as extracellular extractants for Cu, Pb, V and Zn in the sequential elution technique applied to the terrestrial moss Pseudoscleropodium purum

Three experiments were carried out to select the best extractant for use in the sequential elution technique, to enable extraction of Cu, Pb, V and Zn from the extracellular fraction of the terrestrial moss Pseudoscleropodium purum. The optimal concentrations of the extractants tested (CoCl2, NiCl2, Pb(NO3)2, SrCl2, dimercaprol, EDTA, penicillamine) were determined on the basis of the maximum extraction of Zn achieved without any alteration of the plasma membrane. The capacity of these agents (at the optimal concentrations established) to extract the extracellular fractions of Cu, Pb, V and Zn was then evaluated. Extraction with 10 mM EDTA is recommended for all 4 elements considered. As a second option, the use of 50 mM penicillamine is recommended to extract Cu, 30 mM dimercaprol to extract Pb and V and 20 mM NiCl2 to extract Zn. It was also concluded that these results cannot be extrapolated to other cryptogams, and that separate assays are required.