Thermoresponsive polymer-mediated preconcentration for trace analysis

Abstract

Simple and rapid preconcentration techniques using themoresponsive polymers were developed for the determination of traces of organic and inorganic constituents in aqueous solutions. Thermoresponsive polymers, including poly(N-isopropylacrylamide) and poly(vinylmethyl ether), are water-soluble at room temperature, but become sparingly soluble above their critical solution temperatures (ca. 3°C) to form gum-like precipitates. Hydrophobic organic compounds in aqueous solutions were effectively collected on the polymer precipitates, depending on their hydrophobic properties. On the other hand, hydrophilic components remained in the bulk aqueous solutions. Because the polymer phase was highly condensed, the concentrations of analytes were easily increased 100-fold. Hydrated metal ions were converted into hydrophobic chelates with 8-hydroxyquinoline or ammonium pyrrolidine dithiocarbamate, which were successfully incorporated in the polymer phase. Water-soluble charged metal chelates were also concentrated by using adequate counter ions. After dissolving the polymer phase in a small amount of organic solvent, the solution was directly analyzed by HPLC, graphite furnace AAS or ICP-MS. Polymer-mediated preconcentration techniques can also be applicable to the clarification of industrial wastewater.