Determination of dissolved iron(III) in estuarine and coastal waters by adsorptive stripping chronopotentiometry (SCP).

An adsorptive stripping chronopotentiometric (SCP) method has been developed for quantification of dissolved iron in estuarine and coastal waters. After UV-digestion of filtered samples the Fe(III) ions in non-deoxygenated samples were complexed with solochrom violet RS (SVRS). The complexes were then accumulated by adsorption on the surface of a mercury-film electrode. The stripping step was performed by applying a constant current of -17 microA. Sensitivity and detection limit were 15 ms nmol(-1) L (270 ms microg(-1) L) and 1.5 nmol L(-1) (84 ng L(-1)), respectively, for 60-s electrolysis time. Compared with the only other chronopotentiometric method available for measurement of iron in natural waters, our procedure is fifty times more sensitive in a quarter of the electrolysis time. It therefore enables detection of the concentrations currently found in estuarine and coastal waters. The method was successfully used to study the behaviour and seasonal variations of dissolved iron in the Penzé estuary, NW France.