Lead in the form of -for example- Tetra ethyl lead has long been used as fuel additive, ultimately causing soil pollution. There is concern that this lead ultimately settled in wood during the growing process, which may have led to unacceptable concentrations of lead in wood. So, it would be desirable to test wood on lead contents. It appears that this is being done with hand held http://www.niton.com/Portable-XRF-Technology/how-xrf-works.aspx. So I attempted to google for a chemical testing method of wood for lead concentrations but with underwhelming success. So my question is....help.