“…[26][27] Recent work has shown that distinguishing sulfur species of similar oxidation states may be difficult. [28][29][30][31][32][33][34] XANES has been used to measure sulfur speciation in a variety of samples including coal, [35][36][37][38] asphaltenes, 27,[39][40][41][42] kerogen, [43][44][45] bitumen, 41,45 asphalts, 46 petroleum, [47][48] soil, 49 sediments, [50][51] archeological samples, 32 shipwrecks, 52 biochar, 53 plasma cells, 26 and bacteria. 24 XANES measurements on asphaltenes showed that sulfur speciation correlates with molecular weight, with greater sulfoxide abundances found in asphaltenes of lower average molecular weight.…”