FIELD-PROGRAMMED FLOW FIELD-FLOW FRACTIONATION

A flow field-flow fractionation (FIFFF) system capable of accurate and reproducible flowrate programming has been assembled and tested. This modified system consists of three computer-controllable pumps, two th at regulate the incoming and outgoing cross flowrates and one that con trols the channel flowrate. The system also has a computer-linked bala nce that allows for instantaneous measurement of the cross flowrate. P rogramming of the field strength (or cross flowrate) was used to decre ase the analysis time and improve detectability of late eluting peaks in FIFFF analysis. A six component latex mixture, with microspheres ra nging from 20 to 426 nm in size, was used as a test material. With pro gramming, this mixture can be separated in 8 min. (C) 1995 John Wiley & Sons, Inc.