Application of ICP-MS for measuring soil metal cations from sequential extraction

The present work is part of a collaboration between Palermo and Seville Universities to investigate the cations incorporated into calcite and its effect in the trace metal mobility in soils. The study area is located in the central part of Sicily. Calcite is usually greatly dispersed and has a major influence on the pH of soils and therefore on trace element behaviour. A great affinity for carbonates has been observed for a wide range of cations incorporated into calcite. in order to investigate the metal cations in soil carbonate, 1M MgCl2 was used to remove the exchangeable Ca. Sub-samples were treated with acid acetic 1M to quantify the total amount of Ca and metal cations in soil carbonate. And finally others sub-samples were used to perform a kinetic extraction with Na-citrate 0.2M. The ICP-MS was selected as a suitable technique to reliable and simultaneously measure trace elements reducing matrix effects. the equipment used was a X7 SERIES ICP_MS from ThermoElemental (UK). the present work shows in detail the methodology used to determine, in acid acetic and Na-citrate solutions, the following isotopes: Cr, Mn, Fe, Co, Ni, Sr, Ba, Pb and U. We have adapted the US EPA method 6020 for our special needs. it is important to remark that a careful procedure has been carry out to reproduce the sample matrix in all the calibration and QC standards, and so properly select the internal standards since the complexity of the matrix.