On-line solid phase extraction coupled to ICP-OES for simultaneous preconcentration and determination of some transition elements

An on-line solid phase extraction method coupled to ICP-OES was developed for the simultaneous determination of Ce(III), La(III), Sm(III), Y(III), Yb(III), Dy(III), Hf(IV), Zr(IV) and Th(IV) ions in aqueous samples. The ions forming hydrophobic complexes with 3,5,7,2I,4I-pentahydroxy flavone (morin) and were retained on an octadecyl silica (C-18) minicolumn. The adsorbed chelates were subsequently eluted from the column and directly transferred into the plasma with 80% (v/v) propanol:H2O solution for the simultaneous determination of the metal ions. Different parameters affecting the ICP-OES signal intensities and extraction efficiency including pH of the solution, concentration of the chelating agent, flow rate and type of the eluent, loading rate and ionic strength were evaluated and optimized. The calibration graphs were linear in the range of 0.2-100 mu g L-1 and limit of detections for the extraction and determination of the ions in the aqueous sample (25 mL) were in the range 0.10-0.46 mu g L-1. The enhancement factors of the method for the metal ions obtained were in the range of 23 to 242 (V (Sample) = 25 mL) and the precision expressed as relative standard deviations (RSD %) was below 6.9%. Finally, the method was successfully applied to determine the target analytes in natural water samples.