Site selectivity in the deposition and redeposition of polystyrene particles to glass

The site selectivity in the deposition and redeposition of negatively charg ed, polystyrene particles to a glass collector surface was studied under fl ow, by first depositing particles to the collector surface and then removin g them by passing of an air-liquid interface. Using an image analysis syste m, the coordinates of the occupied sites were memorized and subsequently th e probability of redeposition on these sites relative to deposition on othe r collector surface areas was determined. In low ionic strength buffers, 20 and 30 mM KNO3, redeposition probabilities on previously occupied sites we re up to 51 times higher than for deposition elsewhere, while in high ionic strengths buffers (above 30 mM) redeposition probabilities were essentiall y similar as for deposition on other collector surface sites. It is suggest ed that high affinity sites for particle deposition exist on glass, on whic h preferential (re)deposition is mediated through attractive electrostatic interactions. Although such a suggestion is not new, this is the first time supporting evidence has been collected through redeposition experiments as described here, (C) 1998 Academic Press.