Detection of nanocolloids with flow-field flow fractionation and laser-induced breakdown detection

A new nanosize colloid detection method comprised of now-field flow fractio nation (FFFF) with laser-induced breakdown detection (LIBD) is presented, w hich is capable of characterizing the colloid size distribution as well as determining the number density of each size fraction in very low concentrat ions. The method facilitates the detection of aquatic colloids particularly in the lower range of nanometer size (<50 nm) with the sensitivity much hi gher than a laser light-scattering method (LLS), i.e., the lower ppb range. The method is tested with a mixture of polystyrene colloids in three diffe rent nominal sizes, 19, 50, and 102 mn,and the results are compared with th ose of the LLS method. For colloids of 19-nm diameter, the present method d emonstrates the detection sensitivity over 3 orders of magnitude better tha n that of the LLS method. The limitation of the detection sensitivity arise s from the surface bleeding of a ceramic hit overlying the separation chann el of the used FFFF instrument.