Analysis of the aliphatic portion of coal organic materials (COM) was carried out by using ruthenium ion catalyzed oxidation (RICO) of coal, which is capable of converting alkyl side chains attached to aromatic moieties in COM to aliphatic carboxylic acids, whose sp(2) carbons come from their aromatic carbons. One of the most problematic points of RICO reaction is a quantitative analysis of the lower carboxylic acids produced, which are the main products in the reaction of COM. In order to accomplish the above objective, an ion chromatograph was employed in this study. The possible factors affecting the quantitativeness of this reaction were also investigated. Under these optimized conditions, oxidation reactions of Illinois No. 6 (US subbituminous), Akabira (Japanese bituminous), and Zao Zhuang (Chinese bituminous) coals were conducted, the results indicating that the distribution of shorter alkyl side chains (< C-5) of these coals was similar to one another, while longer alkyl side chains (> C-30) are relatively abundant in the lower rank coal. The presence of polymethylene moieties linking two aromatic skeletons was also confirmed by the finding the diacids (C-12-C-25) in RICO reaction of Akabira
