Characterisation of environmental colloids by on-line SdFFF-ETAAS

Colloidal particles (size range 0.001 – 1.0 m) play an important role in many environmental processes: they can strongly bind pollutants and thereby facilitate their transport (i.e. in river systems or in the atmosphere) or enhance their retention (i.e. in soils), depending upon the degree of mobility of the colloids. Many methods have been developed in order to characterize colloidal matter, but the sizing of material in the colloidal range and their chemical characterization is difficult to obtain by a single method. By using Field-Flow Fractionation (FFF) methods1, different size fractions can be collected (across the sample size distribution) for subsequent observation, as for example, heavy metal load determination but the small amount of the sample that can be processed in single separation run is a limiting factor. For these reasons the elemental characterization of the SdFFF separated particle fractions need a very sensitive analytical method, in order to avoid time-consuming concentration steps, with the consequence of a further sample handling procedure. In the present work Electrothermal Atomic Absorption Spectrometry (EAAS) equipped with Capillary Injection Device (CID) is here presented as on-line detection system for SdFFF. The CID allows the direct introduction of the analytical solution into the graphite furnace to an extent of some ten milliliters, thus preconcentrating the colloidal particles on the furnace walls2. The determination of elements as iron, cadmium or cobalt even at pg/g level in the eluate, as such as values for the SdFFF separated fractions of environmental colloids, has been proved to be possible avoiding off-line manipulations.