Metal Standards: Ashing Procedure For Tin
Cleta had some polyepichlorhydrin elastomers which were thought to contain some trace amount of tin in the form of an organotin compound that was used as a catalyst. Paul was asked if he could recommend a sample preparation procedure for these types of samples.
The concern with Sn is loss of the tetrachloride which is quite volatile. A typical procedures requires about 2 grams of sample in a Kjeldahl flask to be heated with 10-20 mL of concentrated sulfuric acid to fumes of SO3, at which point 50% hydrogen peroxide is added dropwise to the boiling mixture. The peroxide is added one drop at a time until the mixture clears. At first, it may seem like this will never happen - exercise patience and proceed slowly.
Please exercise extreme caution since this mixture is very reactive and oxidizing. The use of this procedure to recover Sn organometallic compounds from PVC in large amts of chlorine is reported by Tabern and Shelberg, Ind. Eng. Chem. Ed., 4, 401 (1932).
Please contact me with other questions or comments.
Serving you in chemistry,
Paul R. Gaines, Ph.D.
CEO of Inorganic Ventures & Fellow Chemist
DISCLAIMER: Advice offered by the chemists at Inorganic Ventures is intended for the individual posing the question. Feel free to contact us to verify whether these suggestions apply to your unique circumstances.