A Novel Strategy to Evaluate the Aromaticity Degree of Natural Organic Matter Based on Oxidization-Induced Chemiluminescence

Due to its complex composition and structure, many of the properties of natural organic matter (NOM) are poorly understood. In this study, the oxidization-induced chemiluminescence (OCL) of NOM was investigated, and a flow-injection OCL method was developed using alkaline persulfate-H2O2 as the oxidizing agent. The method is suitable for the direct analysis of NOM in both homogeneous and heterogeneous samples without isolation or concentration. A strong linear relationship (p < 0.001) was found between the normalized organic carbon OCL (OCLOC) and the percentage of aromatic carbon in standard NOM and soil samples, suggesting that OCLOC can be used as an empirical indicator to assess the aromaticity degree of NOM in both homogeneous and heterogeneous samples. By using this method, the percentages of aromatic carbon in a forest soil profile with low organic carbon content were estimated, and a decrease in the degree of aromaticity in deeper soil was observed. Considering the high sensitivity (lower than 0.1 mg C L-1) and throughput (13 s per detection) and low sample consumption (less than 1 mg) of the method, the proposed OCLOC indicator shows great promise for the high-throughput evaluation of the aromaticity degree of NOM for a wide variety of environmental and geochemical samples.