Nanoscavenger based dispersion preconcentration: sub-micron particulate extractants for analyte collection and enrichment

A new approach has been developed for the preconcentration of analytes from solution using nanoscavengers; monodisperse functionalised particles of sub-micron dimensions, that can be suspended as a quasi-stable sol in an aqueous solution, and quantitatively recovered with the analyte by conventional filtration. No external agitation of the sample is required as the particles move naturally through the sample by Brownian motion, convection and sedimentation. By careful choice and control of their particle size and surface chemistries, nanoscavengers can be designed to suit a number of different analytical problems. Surface modification of these nanometre-sized particles, through the grafting of complexing or partitioning functional groups, can produce nanoscavengers having affinities for specific analytes and operating through a wide range of mechanisms from covalent bonding to hydrophobic interaction. The approach is illustrated by the development of an extraction-based preconcentration of metals from solution that employs sub-micron Stober-type silica spheres, the surfaces of which have been modified using chelating diamine and dithiocarbamate groups. The concept has potentially widespread applicability as it is neither limited to metal extractions, nor to the use of silica-based nanoscavengers. Minimal involvement of organic solvents make nanoscavengers a potentially environmentally benign ("green") alternative to many conventional solvent extraction techniques