Mn speciation at nanomolar concentrations with a porphyrin competitive ligand and UV-vis measurements

Aubin Thibault de Chanvalon; George W Luther

doi:10.1016/j.talanta.2019.02.069

Mn speciation at nanomolar concentrations with a porphyrin competitive ligand and UV-vis measurements

Talanta. 2019 Aug 1:200:15-21. doi: 10.1016/j.talanta.2019.02.069. Epub 2019 Feb 25.

Authors

Aubin Thibault de Chanvalon¹, George W Luther²

Affiliations

¹ University of Delaware, School of Marine Science and Policy, 700 Pilottown Road, Lewes, DE 19958, USA. Electronic address: thibault@subatech.in2p3.fr.
² University of Delaware, School of Marine Science and Policy, 700 Pilottown Road, Lewes, DE 19958, USA.

PMID: 31036167
DOI: 10.1016/j.talanta.2019.02.069

Abstract

We describe the modification of the porphyrin method for low-level determination of the speciation of dissolved Mn in seawater. First, an investigation of sensitivity of the method versus the salinity, the reagent composition and the type of ligands present is described for a few micromolar of dissolved Mn. Then, using certified seawater reference standards, we demonstrate the accuracy of the method for total concentrations of manganese between 1 and 10 nM. To this aim, we report the reactivity of solutions made of Mn(II) and Mn(III) bound to Tiron and DFOB with our optimized porphyrin reagent which includes adding excess Cd²⁺, and compare these results with data from representative natural seawater samples. This work describes an improved method that gives the opportunity for future work to investigate Mn speciation at nanomolar concentration in the open ocean.

Keywords: Humic acide; LWCC; Manganese; Speciation; Trace metal.