Determination of heavy metals in soils and sediments by microwave-assisted digestion and inductively coupled plasma optical emission spectrometry analysis

The determination of the total content and the leachable aliquot by aqua regia dissolution of eight heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) in soils and sediments was developed by microwave digestion technique combined with inductively coupled plasma atomic emission spectrometry. A complete digestion of soils and sediments was achieved by using an acid mixture of HF-HCl-HNO3 (1:3:1); the microwave-irradiated closed vessel system used for the determination of aqua regia leachable quota, proved to be a viable alternative to the traditional reflux system. The experimental study was conducted using five BCR standard reference materials (CRM 141R 'Calcareous Loam Soil', CRM 142 'Light Sandy Soil', CRM 143 'Sewage Sludge Amended Soil', CRM 277 'Estuarine Sediment' and CRM 320 'River Sediment') in two laboratories with different microwave ovens and ICP-OES. Calculated recovery, repeatability, and reproducibility confirm the good performance of the procedures adopted. A Nested Design statistical analysis was carried out for both procedures and showed that the major source of variability in the analysis was due to ICP-OES measurements rather than microwave-assisted dissolution. (C) 2000 Elsevier Science B.V. All rights reserved.