An ionic liquid-based sorbent for solid phase extraction of trace iron(III) from biological and natural water samples

A new ionic liquid modified silica gel sorbent was prepared from the reaction of active silica gel with N-3-(-3-triethoxysilylepropyl)-3-methylimidazolium chloride ([(TESP)MIm]Cl). This sorbent was exploited as solid phase extractant for separation and preconcentration of metal ions prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). It was found that it can selectively adsorb Fe(III). Identification of the surface modification was performed on the basis of FT-IR. Experimental conditions for effective adsorption of trace Fe(III) were optimised using both batch and column procedures. At pH 3, Fe(III) could be quantitatively adsorbed and completely eluted by using 2 mL of 0.1 mol L-1 of HCl. 150 mL of sample solution was adopted as the maximum sample volume and a high enrichment factor of 75 was obtained. Most common coexisting ions did not interfere with the separation and preconcentration of Fe(III) at optimal conditions. The maximum static adsorption capacity of the sorbent was 37.0 mg g(-1). The detection limit of the present method was 0.48 mu g L-1, and the relative standard deviation (R. S. D.) was lower than 1.7%. The method was successfully applied to the preconcentration of trace Fe(III) in biological and natural water samples with satisfactory results.