This project concerns investigation and evaluation of various carbonaceous materials for use as a new EPR standard. For over three decades, Varian """"""""weak pitch"""""""" and """"""""strong pitch"""""""" samples have been used as EPR standards. Over the years, the population of these standards has diminished while replacements are not available and no new intensity standards have been forthcoming. In order to meet the need for a good new EPR intensity and g-value standard, coal, fusinite (a coal maceral), and several sugar chars were investigated. Of the prototypical standards prepared, a chemically-treated fusinite is recommended as most suitable based on its chemical homogeneity. Effects of dilution with KBr, KCl, and polymer are negligible. Several model standard compounds have been prepared in a polymer matrix to minimize changes in packing density over time. These sample standards provide repeatable intensity measurements to better than 2.5% intensity, and 1.1% linewidth sample standard deviation. It is very likely that these deviations can eventually be held to less than 0.5%. The synthetic chars thus far studied are less stable than the treated fusinites. However, since it would be desirable ultimately to have a rigorously reproducible synthetic material for a standard, the quest for synthetic standards materials continues.
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