Extraction properties of modified silica gel for metal analysis by energy dispersive X-ray fluorescence

Batch-wise liquid-solid extraction using chemically modified silica was studied as a separation method for non-essential heavy-metals, such as cadmium, lead and mercury, with subsequent X-ray fluorescence analysis. Silicas modified with zirconium phosphate (SiZrP) and propyl imidazol (SiIm) were prepared for use as a solid extractor. The silica modified with imidazol groups showed a high selectivity for Hg2- and a wide linear response range (0.5 - 50 mg L-1) with a preconcentration factor of 107, but did not adsorb significant amounts of lead and cadmium. For the SiZrP system the preconcentration factors for all studied metal ions were between 43 and 47, with lower selectivity. The sensitivity depends on the characteristic emission line of each element. The linear response ranges were 0.5 to 10 mg L-1 for cadmium, 0.5 to 50 mg L-1 for lead and 0.5 to 116 mg L-1 for mercury. The stability presented by the materials were excellent, allowing reuse after regeneration in an acid media.33102005202