Strong copper (II) species in estuarine and sea waters investigated by a method with high detection window.

The distribution of copper(II) in species of different stability in some estuarine and sea water samples (Adriatic Sea) was investigated by a method based on the sorption of the metal ion on a strongly sorbing resin, Chelex 100, whose sorbing properties have been previously characterized. From them, it is possible to predict very high values of detection windows at the considered conditions, for example side reaction coefficient as high as 1010 at pH 7.5. Strong copper(II) species in equilibrium with Chelex 100 were detected, at concentration 2–20 nM, with a reaction coefficient approximately 1010.6 at pH 7.45 in sea water, strictly depending on the acidity. They represent 50–70% of the total metal ion and are the strongest copper(II) complexes found in sea water. Weak complexes too were detected in all the samples, with reaction coefficient lower than ca. 109 at the same pH. The method applied, named resin titration (RT), was described in a previous investigation, and is here modified in order to be carried out on oceanographic boat during a cruise in the Adriatic Sea.