title: Study on steric transition in asymmetrical flow field-flow fractionation and application to characterization of high-energy material.
abstract: In field-flow fractionation (FFF), there is the 'steric transition' phenomenon where the sample elution mode changes from the normal to steric/hyperlayer mode. Accurate analysis by FFF requires understanding of the steric transition phenomenon, particularly when the sample has a broad size distribution, for which the effect by combination of different modes may become complicated to interpret. In this study, the steric transition phenomenon in asymmetrical flow FFF (AF4) was studied using polystyrene (PS) latex beads. The retention ratio (R) gradually decreases as the particle size increases (normal mode) and reaches a minimum (Ri) at diameter around 0.5μm, after which R increases with increasing diameter (steric/hyperlayer mode). It was found that the size-based selectivity (Sd) tends to increase as the channel thickness (w) increases. The retention behavior of cyclo-1,3,5-trimethylene-2,4,6-trinitramine (commonly called 'research department explosive' (RDX)) particles in AF4 was investigated by varying experimental parameters including w and flow rates. AF4 showed a good reproducibility in size determination of RDX particles with the relative standard deviation of 4.1%. The reliability of separation obtained by AF4 was evaluated by transmission electron microscopy (TEM).
authors.affiliation: Department of Chemistry, Hannam University, Daejeon 305-811, South Korea.
authors.forename: Haiyang
authors.initials: H
authors.lastname: Dou
authors.forename: Yong-Ju
authors.initials: YJ
authors.lastname: Lee
authors.forename: Euo Chang
authors.initials: EC
authors.lastname: Jung
authors.forename: Byung-Chul
authors.initials: BC
authors.lastname: Lee
authors.forename: Seungho
authors.initials: S
authors.lastname: Lee
mesh_terms: D000465:Algorithms; D053834:Explosive Agents / Q000302:isolation & purification*; D031521:Fractionation, Field Flow / Q000379:methods*; D008863:Microspheres; D010316:Particle Size; D011137:Polystyrenes / Q000737:chemistry; D015203:Reproducibility of Results; D014227:Triazines / Q000302:isolation & purification*
chemical_list: D053834:Explosive Agents; D011137:Polystyrenes; D014227:Triazines; C009160:cyclonite
keywords: Asymmetrical flow field-flow fractionation (AF4); Normal mode; RDX particles; Steric transition; Steric/hyperlayer mode