Stable isotopic studies of organic matter have been used to interpret the relative amounts of terrestrial and marine organic matter of present and past environmental and atmospheric conditions and, as such, can provide important clues to conditions at various times in Earth's history. However, the techniques that have been available to date include either a bulk analysis or a compound-specific analysis.

In "Influence of maceral content on δ¹³C and δ¹5N in a Middle Pennsylvanian coal," Sue Rimmer and her co-authors show an approach to isotopic analysis: the maceral-specific approach. By separating individual organic components from a rock or coal using density-gradient centrifugation (DGC) (a technique adapted from biology), the authors were able to determine the bulk isotopic composition of relatively pure (>95%) end-members and could track isotopic shifts in single components, removing any uncertainly about composition. The authors discuss how they "pulled apart" the components of a coal which were found to have significant differences in isotopic composition. They noted how variations in the relative amounts of different components would "skew" the bulk isotopic composition of a rock or coal. 

Sue Rimmer is an associate professor and director of graduate studies in the Department of Earth and Environmental Sciences in the College of Arts & Sciences at the University of Kentucky. She earned a bachelor’s degree from Southern Illinois University, a master’s degree from the University of Illinois, and a doctorate from Penn State University. Her research interests are organic petrology and sedimentary geochemistry, working primarily on coals and petroleum source rocks.  Rimmer is currently one of the only faculty members in the United States teaching organic petrology in a university setting.