Hollow-Fiber Flow Field-Flow Fractionation

Field-flow fractionation (FFF) is a family of separation techniques able to fractionate a broad range of macromolecules, nano- and micro-sized particles of different origin. Among FFF, flow FFF (FlFFF) shows the highest separation versatility, and today it is the only FFF technique with significant market relevance. Commercial FlFFF employs macro-scale, flat-type channels. The idea of hollow-fiber (HF) membranes as tubular, micro-column channels for FlFFF (HF FlFFF) dates back 1974, with fundamentals on HF FlFFF given only in the late 1980s, and outstanding applications reported only over the last ten years. Compared to standard FlFFF, the key advantage of HF FlFFF lies in the instrumental simplicity and low-cost of the fractionation device, and in the low volume able to favor on-line coupling with orthogonal methods. Last-generation HF FlFFF has been successfully applied to macromolecules and particles such as proteins and whole cells, and shown particularly suited to be coupled with time-of-flight (TOF) mass spectrometry (MS) for intact protein profiling and characterization. We review basics on HF FlFFF theory and instrumentation, the early investigations, and the most recent technical and methodological developments that have improved HF FlFFF to a performance normally achieved by conventional FlFFF.