This research, supported by the Analytical and Surface Chemistry Program, is focused on the development of Field Flow Fractionation (FFF), a technique based on the use of orthogonal force fields to separate large molecules and small particles. The analyte mixture is pumped into a rectangular channel, and a force is applied 90 degrees relative to the direction of flow. In particular, this grant will explore the use of thermal gradients and gravitational forces to effect the separation. In addition, analytical split flow thin cell (SPLITT) fractionation, a method where the separation occurs along the channel width, and where splitters are used at one or both ends of the channel, is investigated to determine it's potential for analytical separations. Here, the separation is based on hydrodynamic lift forces, which allows characterization of species based on diffusion coefficients. These techniques can be used to characterize a variety of biological and synthetic materials. This grant in the Analytical and Surface Chemistry Program will support research into improved methods for the separation of large molecules and small particles using field flow fractionation. This is a procedure invented by Professor Giddings in which crossed force fields are used to separate small (micron-sized) particles or molecules based on differences in shape, density, and electrical characteristics. This methodology will have wide-ranging applications in the fields of biotechnology and materials science.