Composite materials based on hybrid mesoporous solids for flow through determination of ultratrace levels of Cd(II)

"In this work we present a solid phase extraction (SPE) flow through system coupled to graphite furnace atomic absorption spectrometry (GFAAS) for the determination of Cd(II) at ultratrace levels. The flow system holds a minicolumn which was filled, one in turn, with three different lab made materials: a) mesoporous silica functionalized with 3-aminopropyl groups from 3-aminopropyl triethoxysilane (HMS); b) HMS with a resin, Amberlite IR120; c) HMS-Amberlite IR120 and polyvinyl alcohol (PVA). All the solids were characterized by FTIR and SEM. Batch experiments were performed in order to study the optimum adsorption pH, the adsorption kinetics and the maximum adsorption capacity.The materials were compared in terms of their aptitude for the pre-concentration of the analyte under dynamic conditions. Microvolumes of HCl were employed for the release of cadmium and its introduction into the electrothermal atomizer. The operational variables of the flow system were also tested and optimized. The comparison of the figures of merit revealed HMS-A-PVA as the best option from an analytical point of view: limit of detection= 4.7 ng L-1, limit of quantification= 16 ng L-1, RSD %= 4 (n =6, 100 ng L-1), linear range: from LOQ up to 200 ng L-1 and a lifetime over 600 cycles with no obstructions to the free movement of fluids, material bleeding or changes on the analytical sensitivity. The proposed method was shown to be tolerable to several ions typically present in natural waters and was successfully applied to determination of trace of Cd(II) in real samples. A full discussion of the main findings with emphasis on the interaction metal ion/fillings will be provided."