Combination of gravitational SPLITT fractionation and field-flow fractionation for size-sorting and characterization of sea sediment

A combination of gravitational split-flow thin (SPLITT) fractionation and sedimentation/steric field flow fractionation (Sd/StFFF) has been used for continuous size-sorting of a sediment sample and for size analysis of the collected fractions. An IAEA ( International Atomic Energy Agency) sediment material was separated into four size fractions (with theoretical size ranges < 1.0, 1.0-3.0, 3.0-5.0, and > 5.0 mu m in diameter) by means of a three-step gravitational SPLITT fractionation (GSF) for which the same GSF channel was used throughout. The GSF fractions were collected and examined by optical microscopy (OM) and by Sd/St FFF. The mean diameters of the GSF fractions measured by OM were within the size interval predicted by GSF theory, despite the theory assuming that all particles are spherical, which is not true for the sediment particles. The Sd/St FFF results showed that retention shifted toward shorter elution time ( or larger size) than expected, probably because of the shape effect. The results from GSF, OM, and Sd/StFFF are discussed in detail.