Separation of particulate environmental samples by SPLITT fractionation using different operating modes

Procedures for gentle preseparation of particle suspensions prior to sedimentation field flow fractionation (SdFFF) analysis based on the use of Split-flow thin cell (SPLITT) fractionation (SF), were examined for isolating size fractions from both polydisperse standard silica samples and natural river particle samples. Two modes of SPLITT cell operation (conventional SF, full feed depletion SF (FFDSF)) are discussed and their performances compared. Recycling procedures for enhancing the resolution were tested and the degree of the separation attained was checked by optical microscopy and, in the case of the natural river particle samples, by coupling SdFFF with scanning electron microscopy (SEM) of the fractionated samples. The FFDSF has the advantage that no external dilution is introduced during the binary separation, so that the total sample concentration is unaffected and the separation obtained appears to be equally good for the two methods.