REVISION OF THE REGULATORY SEMISPECIFIC METHODS FOR THE DETERMINATIONOF SURFACTANTS IN AQUEOUS SAMPLES .2. ANIONIC SURFACTANTS

Two analytical protocols for the determination of MBAS (Methylene Blue Active Substances) in environmental aqueous samples, respectively pro posed by the Italian CNR Water Research Institute (IRSA) and by the In ternational Organisation for Standardisation (ISO), were compared to d isclose the most remarkable differences. A revision of the present reg ulatory method (IRSA E-017) for the determination of anionic surfactan ts in waters was undertaken. Improvements of the current procedure wer e proposed regarding the choice of reference material and the employme nt of a specific calibration curve for quantitation of MBAS in surface waters. Laboratory experiments were carried out on both synthetic and real water samples in order to evaluate precision and accuracy of the method. The experimental results showed that the MBAS method overesti mates the anionic surfactant content in waste water samples from a mec hanical-biological sewage treatment plant, especially in the final eff luent.