Chromium interaction with O-donor humic-like ligands using electrospray-ionization mass spectrometry

The study of the interaction of chromium with O-donor humic-like ligands is performed by electrospray-ionization mass spectrometry (ESI-MS) and ultraviolet/visible (UV/VIS) spectrophotometry. Heterogeneity of functional groups justifies the use of model compounds of humic substances. For studying the interaction of chromium with humic substances as model substances were used benzoic, salicylic, phthalic and citric acid, which include O-donor atoms, also present in heterogenous and polydispersed ligands, such humic and fulvic acids are. The intensity of the interaction is correlated with the acid-base and electron-donor properties, geometric and steric characteristics, and the number and the positions of O-donor atoms in the investigated ligands. UV/Vis data describing chromium interaction with humic-like ligands is placed in correlation with the ESI-MS data of the complexes, both in quantitative and in qualitative terms. UV/VIS spectroscopy and ESI-MS quantification showed a large difference in the informativeness of describing the interaction of chromium(III)-ligand, in favor of ESI-MS technique. ESI-MS technique can be used for quantitative analysis of the system Cr(III)-ligand. ESI-MS ion current chromatograms of 20 μL loop injections of systems Cr(III)-ligand, indicate a stabile peak and signal integrity.