Field-flow fractionation coupled to multi-angle laser light scattering detectors: Applicability and analytical benefits for the analysis of environmental colloids

Results from the analysis of natural colloid with a coupling of field-flow fractionation (FFF) with multi-angle laser light scattering photometers (MALLS) are presented. The results indicate that after FFF of natural colloids MALLS is applicable to retrieve independent and absolute particle sizes (RMS radius or radius of gyration) for the colloids fractionated. For the analysed samples of soil colloids the appropriate data processing in MALLS is the linear or second order ZIMM fitting method for particle sizes up to 500 nm in diameter. This is in contrast to the MALLS analysis of latex beads, where the ZIMM fitting method produces reliable results only below ∼100 nm in diameter. The reason for the good results for the soil colloids can be found in the behaviour of the particle form factor P(θ) which was found to be linear function when plotted as Kc/R(θ) over sin2(θ/2).