Solid-phase spectrophotometric and test determination of silicate in natural water.

Quaternary ammonium salts (QAS) of aliphatic (tetradecylammonium nitrate) and heterocyclic (lucigenine) nature immobilized onto silica surface have been proposed as effective anion-exchangers for the adsorptional extraction of silicate in the form of the reduced molybdo-silicic heteropoly anion for the successive determination in the solid phase by using spectrophotometric and visual test techniques. The interface interaction has been investigated. On the basis of the results obtained the new solid-phase spectrophotometric and visual test techniques for the direct silicon determination in the rage of its concentrations 14-400 μg L(-1) have been proposed. The tolerance limits of the major components in natural waters and other ions capable of producing heteropoly anions in the silicate determination have been reported. The techniques have been successfully applied for the silicate determination in natural waters.