Modification of the sequential elution technique for the extraction of heavy metals from bryophytes

The sequential elution technique S.E.T.. has frequently been used to determine the distribution of metals at different cellular sites in contaminated lichens and, to a lesser extent, in mosses. Here we evaluate certain aspects of the technique in order to improve the reliability of the results obtained when it is used on bryophytes. Various experiments were carried out using the aquatic moss Fontinalis antipyretica Hedw. Results confirmed that two consecutive washings are sufficient to ensure total extraction of the extracellular metal. In addition, the possibility of using new extractants to remove the metal that is accumulated at extracellular sites was investigated. Although NiCl2 the extractant originally used by the authors of the technique wBrown DH, Buck GW. J Briol 1978a;10:199]209; Brown DH, Buck GW. Ann Bot 1978b;42:923]929x. was adequate for metals with low affinity for the binding sites, EDTA and Pb NO3.2 were more efficient for the extraction for metals with a medium-high affinity for extracellular binding sites. The optimum concentrations of extractant were found to be 10 or 20 mM for NiCl2 and EDTA, and 50 mM for Pb NO.2.