ELECTROCHEMICAL ESTIMATION OF THE DOMINANT TYPE OF SURFACE-ACTIVE SUBSTANCES IN SEAWATER SAMPLES USING O-NITROPHENOL AS A PROBE

A simple electrochemical method is developed for direct estimation of the concentration and nature of the dominant type of surface active su bstances (SAS) in natural waters using o-nitrophenol (ONP) as a probe. It was noticed from studies of model systems of selected adsorbable o rganic substances (humic and fulvic acids, carbohydrates, proteins and lipids), representative of the chemical composition of organic matter in natural waters, that different surface active molecules influence the polarographic oxidation-reduction processes of ONP in very specifi c ways. This is indicated by different shapes and peak potentials as w ell as by the change of the peak height of the ONP reduction peak in t he presence of different SAS. The application of the method is demonst rated on a number of seawater samples collected at different locations , depths and seasons in the Adriatic sea. Results were compared with t he measurements of surfactant activity values by alternating current v oltammetry and discussed on the basis of the DOC values of the samples .