Use of Soluble Filters for Preconcentration of Trace Elements in Water

Trace elements can be enriched by collecting them on a solvent-soluble filter, followed by dissolution of the filter in a small volume of suitable solvent. The filter serves not only as a sieve but also as a sorbent. For the element to be sorbed, it must be converted into an electrically neutral, hydrophobic species. Ionic species are poorly retained by the filter, but made collectable by adding counter ions with hydrophobic groups. In effect, this enrichment method resembles solvent extraction, but has many advantages. A number of papers have been published on its application since our proposal in 1984. This article summarizes applications of this method and presents a brief description of the mechanism of retention by the filter and some points which may help those who attempt to apply this method to their own field.