DETERMINATION OF TOTAL PHOSPHORUS IN SOAPS/DETERGENTS BY ION CHROMATOGRAPHY

The quantitative determination of phosphorus in soaps and detergents is a classical analytical problem owing to the complexity of the matrix containing a variety of chemical species (i.e., surfactants, complexones and/or zeolites, optical whiteners, perfumes, etc.). A new method has been developed for the analysis of total phosphorus in soaps and detergents which employs UV photolysis of the analyte. It has the advantages that it is a simple procedure and has very low blank values because of the small amount of reagent required for the sample pretreatment. Different types of soaps and detergents were subjected to oxidative UV photolysis. It was found that the organic matrix was degraded in about 60 min, thereby permitting the quantitative analysis of various inorganic species, especially the phosphate ion. Soaps and detergents of different ''types and brands'' were found to contain phosphate from a few mg/l or mg/kg to the 1% level. The results were compared with those obtained by conventional alkaline fusion followed by reduction to molybdenum blue, and were found to be in good agreement.