Determination of iron speciation by cathodic stripping voltammetry in seawater using the competing ligand 2-(2-thiazolylazo)-p-cresol (TAC)

A new sensitive competitive ligand exchange-adsorptive cathodic stripping voltammetric (CLE-ACSV) method for the determination of iron speciation in seawater has been developed using the iron binding ligand TAC 2-(2-thiazolylazo)-p-cresol. An earlier method for determining iron using TAC [1] was reexamined and optimized for measurements in seawater at pH 8.0. The sensitivity was improved by employing a fast (10.12 V/s) linear sweep scan waveform. The detection limit (3σ of blank) is 0.10 nM after an adsorption time of 300 s; the detection limit can be lowered, however, by using a longer deposition time or for the determination of total iron, by increasing the pH to 8.5. This method was applied to samples from Swedish coastal waters and the results indicate the possible efflux of iron binding ligands from sediments in coastal waters.