Ultraviolet spectroscopic analysis for following the biodegradation of hydrotropes

The standard methylene blue colorimetric method for the analysis of ppm concentrations of anionic detergents is sensitive to the chain length of the hydrophobic portion of the molecule. The response to this method is not quantitative among alkylbenzene sulfonates when the alkyl chain is shorter than about eight carbon atoms, and becomes essentially zero with the sulfonates of benzene, toluene and xylene. Although these low molecular weight aromatic sulfonates have few detergency properties, their function and substantial commercial use as solubilizers in detergent formulations lend some importance to a study of their biodegradability. Ultraviolet spectroscopic analysis was successfully applied to the study of the biodegradation of these compounds both in a synthetic medium‐sewageinoculated system and in the well‐known river die‐away procedure. Sensitivity to below 1 ppm was obtained from absorption bands between about 220 and 230 mƁ. Bands were also utilized near 260舑270 mƁ for those compounds having significant absorption in this region. Information concerning changes in functional group substitution and aromatic degradation was obtained from monitoring these two band systems during the biodegradation period.