Determination of trace metal fractionation in aqueous solutions using a solid phase extraction flow injection system on-line coupled to ICP-AES

Speciation analysis has gained in importance during the last years. This can be attributed to the increasing awareness of the influence of speciation of trace metals on their ecotoxic potential. Therefore, analytical methods for trace metal quantification with the additional option to distinguish between different species have to be developed. The presented fractionation method employs a Flow-Injection system consisting of three cartridges packed with different Solid-Phase-Extraction sorbents, namely a reversed phase sorbent, an anion exchange material and a cation exchanger. By passing the sample sequentially through these cartridges, the corresponding complexes are retained and thereby separated into a neutral, an anionic and a cationic fraction. Afterwards they are eluted directly into the nebulizer unit of the detecting ICP-AES. The resulting transient signals of the elution profile are recorded and evaluated to acquire both, the total metal concentrations and the distributions into the three mentioned classes in one measurement. By aiming for a higher degree of automatization, the presented method minimizes potential sources of error. Due to the occurring pre-concentration, enhanced detection limits could be achieved for the investigated elements Mg, Al, Ca, Cr, Mn, Fe, Co, Cu, Zn, Cd and Pb, which were analyzed simultaneously. The accuracy of the method was verified using standard addition series and the applicability of the technique to molten snow samples was demonstrated.