Abstract: A reusable extractor for obtaining a representative sample of the exchangeable ions from a complex heterogeneously saturated ion exchange system such as soil or other complex and colloidal matrices at various oxidation-reduction potentials without the need for costly extraction and purification steps. The extractor comprises a microporous dialysis membrane tube filled with cation- or anion-exchange resin beads. Extraction is effected by equilibrating homoionically saturated ion-exchange resin beads with a sample of the complex matrix under study. The extractor enables simple, rapid, multiple-element assays and provides the new capability of extracting exchangeable ions from stream, lake, and marine sediments in situ.