Sn and Tl Soil Extraction

Teresa has been doing some method development on Sn and Tl in soils. She noticed that her recovery on various CRMs is very low, having done both nitric acid and aquaregia preps. She hoped Paul might lend some information about tin and thallium extraction.

	RE: Sn and Tl Soil Extraction Dear Teresa,      It is likely you are dealing with soils containing the stannic (SnIV) and thallic Tl (III) oxides. These forms of these metals are very resistant to attack by any acid - even HF. Unfortunately, if you are looking for total Sn and Tl and not just 'extractable' Sn and Tl as per the acid extraction EPA methods, you must do the following: Fuse your sample with about a 20 to 1 ratio of sodium carbonate to soil at 1000 deg C for about 15 minutes in a Pt crucible. Dissolve and dilute the sample fuseate using 1/1 HCl/water. For compatibility and stability information for Tl and Sn, check out our Analytical Periodic Table.      I hope this helps. It is unfortunate that there are no acid extraction methods short of high-pressure (2000psi) nitric acid microwave digestions that would even stand a chance.     Paul R. Gaines, Ph.D. Serving you in chemistry