Natural ligands compete for the metal with the ligand used for CSV. This is the basis for the ligand competition method that is used to determine metal speciation in natural waters. The analytical procedure is essentially the same as that used for normal CSV, but the concentration of the added CSV-ligand may be adapted to optimise the competition. For details look in the original method papers. This method has been used to determine the complexation of copper, iron, cobalt and zinc in seawater.

We are currently working on an improvement to the method for Fe speciation in the presence of SA. Here a titration of a sample, carried out by Mahmoud Alhajia. The curvature is indicative of complexation of iron by a ligand present at a concentration of 1.5 nM with a value for log K’FeL of 21.1

Relevant references

Laglera, L. M., G. Battaglia and C. M. G. van den Berg (2007). "Determination of humic substances in natural waters by cathodic stripping voltammetry of their complexes with iron." Analytica Chimica Acta 599(1): 58-66.

Laglera, L. M. and C. M. G. van den Berg (2007). "Wavelength Dependence of the Photochemical Reduction of Iron in Arctic Seawater." Environmental Science & Technology 41(7): 2296-2302.

Laglera, L. M. and C. M. G. van den Berg (2009). "Evidence for geochemical control of iron by humic substances in seawater." Limnology and Oceanography 54(2): 610-619.

Yang, R. and C. M. Van den Berg (2009). "Metal complexation by humic substances in seawater." Environ Sci Technol 43(19): 7192-7197.

Laglera, L. M., G. Battaglia and C. M. G. van den Berg (2011). "Effect of humic substances on the iron speciation in natural waters by CLE/CSV." Marine Chemistry 127(1-4): 134-143.

Abualhaija, M. and C. M. G. Van Den Berg (2013). "Iron speciation in seawater by catalytic stripping voltammetry using salicyl aldoxime." Marine Chemistry submitted.