Cathodic stripping voltammetry determination of chemical reactive iron in coastal seawater

Iron (Fe) is an essential micronutrient for the growth of marine phytoplankton and a key factor to affect marine primary productivity. Chemical reactive iron (CrFe), one of the main components of dissolved iron, is closely related to the absorption of marine organisms. In this study, cathodic stripping voltammetry (CSV) was used for the highly sensitive detection of CrFe using 2,3-dihydroxynaphthalene (DHN) as the complexing ligand and KBrO₃ as the catalyst. A standardized procedure for the detection of CrFe was constructed by optimizing the concentration of various reagents as well as electrochemical parameters. A linear response was obtained in the concentration range 1 ~ 1000 nmol/L under the optimized conditions, and the detection limit of this method was 0.18 nmol/L. This method was validated by iron determination in standard seawater CASS-5 and NASS-6, and the results were in agreement with the certified values. Furthermore, this method was successfully used to determine CrFe at 18 different salinity station sites in the Shandong Peninsula with satisfactory results.