CHARACTERIZATION OF ORGANIC-MATTER IN FRACTIONATED SEAWATER SAMPLES USING O-NITROPHENOL AS AN ELECTROCHEMICAL PROBE

In the presence of adsorbed layers of organic matter on the mercury el ectrode, the electrochemical characteristics of o-nitrophenol (ONP) ch ange in significantly different ways, depending on the different prope rties of organic substances like hydrophobicity, acidity, molecular we ight, etc. Based on this phenomenon, a method was developed to roughly characterize surface active organic matter in seawater samples by mea suring the changes in ONP peak and prepeak heights, and shifts of peak potential The method was improved by fractionation of seawater sample s on the XAD-8 resin in hydrophobic basic and neutral, hydrophobic aci d and hydrophilic organic fractions. To better understand the behaviou r of natural seawater samples, sorption properties of different model substances on the XAD-8 resin, particularly those of acidic polysaccha ride hyaluronic acid and protein albumin have been investigated. The o btained results have shown that hyaluronic acid is distributed between the hydrophilic and hydrophobic acid fractions in the ratio of ca. 80 and 20%, respectively. Albumin is going almost completely into the hy drophobic acid fraction. The results on the sorption properties of oth er model surface active substances, representatives of other major gro ups of organic substances in marine samples, were published earlier [I ]. The advantages of the fractionation are the separation of hydrophob ic acid from hydrophilic organic material, which enables distinguishin g between adsorption effects of acidic polysaccharides and fulvic acid s, and obtaining better distinction of proteins from other organic com pounds. Three seawater samples from the Adriatic Sea were used to demo nstrate the applicability of the method. All the samples and fractions were compared to dissolved organic carbon (DOG) values.