Development of an SdFFF-ETAAS hyphenated technique for dimensional and elemental characterization of colloids.

Direct hyphenation of Electrothermal Atomic Absorption Spectroscopy (ETAAS) to Sedimentation Field Flow fractionation (SdFFF) was developed to allow an elemental characterization of submicronic particles as a function of the size. This hyphenation is particularly suitable for characterizing colloidal particles of environmental interest such as water-borne particles. The interface consists in employing an automatic Capillary Injection Device (CID) which allows the direct introduction of large and variable volumes of colloidal particle suspensions into a hot graphite furnace, thus preconcentrating the colloidal particles on the furnace walls. The method was validated by using certified submicronic Fe2O3 with reference to Fe determination. The procedure was set up by first optimizing the SdFFF fractionation under programmed field conditions thus allowing an optimum fractionation operation with respect to the particle size. The ETAAS procedure was then tested to determine whether it could directly analyze slurry Fe2O3 solutions without the need for a mineralization step. Subsequently, the CID coupled to ETAAS was exploited in its ability to enhance the sensitivity because of the increased injection volume. Statistical tests and data handling were carried out to prove the suitability of the ETAAS-CID module. Finally, off-line and on-line coupling experiments of ETAAS-CID–SdFFF hyphenation were made. These experiments highlighted the advantages of the on-line coupling since it allows a synchronized sampling, enrichment and elemental analysis of the flowing eluate. The benefits of the proposed hyphenation are the great specificity of the analytical detection, increased sensitivity, analysis time reduction and minimum sample handling and contamination.