On-line particle concentrator with upstream ultrafiltration in continuous SPLITT fractionation

An upstream ultrafiltration (UU) method is employed for the on-line concentration of collected particle fraction and for the convenient regulation of flow rates in split-flow thin (SPLITT) fractionation. Concentration of the collected panicle fraction is necessary to fractionate particles by smaller cutoff diameters in SPLITT fractionation. By introducing a simple device utilizing upstream ultrafiltration with tangential flow, particle solution collected at each SPLITT outlet can be simultaneously concentrated within the device during the run without the need of a separate centrifugation. Since a needle valve can be implemented at the outlet of the particle concentrator using upstream ultrafiltration (PCUU), it provides a great convenience with an accuracy in adjusting outlet flow rates of the SPLITT channel, and it eventually brings accurate control of cutoff diameter in SPLITT fractionation of a micrometer-sized particle sample. Moreover, the volume of carrier solution required for SPLITT fractionation, especially for a high-speed SPLITT run, can be minimized by circulating the filtrate solution of PCUU into the carrier reservoir directly. The advantage of on-line particle concentration is demonstrated by utilizing a slow flow feed technique for the fractionation of an incinerator fly ash particle sample to obtain a highly efficient SPLITT separation.