Particle size analysis of dilute environmental colloids by flow field-flow fractionation using an opposed flow sample concentration technique

An on-line concentration method has been developed for the analysis of dilute suspensions of macromolecules and particles by flow field-now fractionation (FFF). This method, termed opposed now sample concentration (OFSC), uses two opposing flowstreams to focus sample into a narrow band near the inlet of the now FFF channel. Large sample volumes (up to 1 L) have been successfully loaded, concentrated, and separated in a 1 mt volume now FFF channel. Concentration factors as high as 10(5) have been achieved. The effectiveness of OFSC now FFF was demonstrated using mixtures of monodispersed standards such as proteins and polystyrene latex beads. Retention times, peak areas, and resolution are comparable for a 10 mt and a typical 10 mu L injection volume. The applicability of the method to environmental studies was demonstrated by a separation of river water colloids.