There are four techniques that are generally used for the determination of metals: ICP, AAS, XRF and NAA. We have modern instrumentation for each of these at the ASU and ASG laboratories.
At the ASU, the majority of metal analyses are carried out using ICP and AA. These instruments require samples to be in a solution form and a variety of different heating/acid digestion methodologies are employed to achieve this.
At the ASU, our soil sample preparation and digestion methodology is based on the USEPA method 200.7, "Trace Elements in Water, Solids and Biosolids by Inductively Coupled Plasma-Atomic Emission Spectroscopy".
In this method a mixture of concentrated hydrochloric and nitric acids are employed to extract and dissolve metals (and certain non-metals) from the matrix. In this process, certain metals such as Cu, Pb and Zn are extracted almost exhaustively (90-100%). However, silicates are largely unaffected.
Typically the preparation of soil samples for analysis is a two to three day procedure.