REVISION OF THE REGULATORY SEMISPECIFIC METHODS FOR THE DETERMINATIONOF SURFACTANTS IN AQUEOUS SAMPLES .1. NONIONIC SURFACTANTS

A survey of the semispecific methods for the analysis of nonionic surf actants in waters is given, including the BIAS Bismuth Iodide Active S ubstances) one, which is currently required by the Italian legislation . Two analytical protocols for the determination of BIAS in environmen tal samples, proposed by the Italian CNR Water Research Institute (IRS A) and by the International Organisation for Standardisation (ISO), re spectively, were compared to disclose the most remarkable differences. A series of experiments was carried out to solve the inconsistencies of the two procedures and to evaluate the previously never reported pr ecision and accuracy of the method over the tested concentration range . Applied to the analysis of raw and treated wastewaters, the BIAS pro cedure was found to significantly overestimate the real nonionics conc entration particularly in the final effluents, thus exhibiting a poor accuracy. Finally, a revised IRSA protocol of the BIAS method was prop osed whose precision is around 10% and 5% for BIAS levels up to 0.1 mg /L and > 0.15 mg/L, respectively.