The Role of Reference Materials in Trace Element Speciation
Dr. Zoltán Mester
Group Leader Chemical Metrology
Institute for National Measurement Standards
Friday, April 5, 2013
C2-361 (Reading Room)
Abstract: An overview of the current state of the art of Se speciation will be given with a special focus on associated Certified Reference Material (CRM) development. The example of SELM (selenium enriched yeast reference material) CRM will be used to demonstrate the developmental challenges and appropriate use of these materials.
Saccharomycescerevisiae and many other microorganisms have the remarkable ability to accumulate large quantities of metallic/metalloid elements. This ability has been exploited for the production of yeast based mineral supplements which have been used for decades. However, the efficacy/toxicity of trace elements depends on its chemical form (i.e. speciation).
Using high resolution orbitrap mass spectrometry the selenium analogs of the key metabolites of the sulfur amino acid pathway has been identified in selenium enriched yeast. Oxidized forms of selenocysteine, selenohomocystine, selenoglutathione, seleno-?-glutamyl-cysteine, N-(2,3-dihydroxy-1-oxopropyl)-selenocysteine, N-(2,3-dihydroxy-1-oxopropyl)-selenohomocysteine, selenomethionine, seleno-S-adenosylhomocysteine, the conjugate of glutathione and N-(2,3-dihydroxy-1-oxopropyl)-selenocysteine, and many others were identified in Se enriched yeast.
Additionally as sizeable portion of Se in Se enriched yeast is actually in the zero valent form in nanometer sized deposits as identified using a various synchrotron based X-ray imaging techniques and nano secondary ion-mass spectrometry.