In situ growth of Fe3O4 nanoparticles for dispersive magnetic micro-solid phase extraction of cadmium followed by ETAAS detection

In this work, a new method based on dispersive magnetic micro-solid phase extraction (DM-mu-SPE) of Cd prior to its determination by electrothermal atomic absorption spectrometry (ETAAS) is described. The method is based on the co-precipitation of Cd at the parts-per-trillion level onto freshly prepared Fe3O4 nanoparticles by applying high intensity sonication to the aqueous sample containing a Fe(II) + Fe(III) mixture together with the target analyte. The resulting magnetic solid phase can be easily separated from the sample using a magnetic field, and hence, no filtration or centrifugation steps are necessary. After redispersion, a volume of the slurry is injected into the graphite tube for atomization, thus avoiding the elution step. A co-precipitation mechanism of Cd on nanosized magnetite is approached using the Berthelot-Nernst and the Doerner-Hoskins laws. Cd is trapped by occlusion during the formation of Fe3O4 NPs. Under optimal conditions, a detection limit of 2.3 ng L-1 Cd is obtained. An enrichment factor of 53 is achieved. A study carried out on spiked natural water samples shows recoveries in the range of 98.2-100.3%.