A study of chromium interaction with N-donor ligands using electrospray-ionization mass spectrometry

Abstract

A study of the interaction of chromium(III) with 2'2-bypiridine and two pesticides, atrazine and acetamiprid, as N-donor ligands was performed using electrospray-ionization mass spectrometry (ESI-MS) and ultraviolet/visible (UV/Vis) spectrophoto¬metry. Atrazine and acetamiprid, both widely used pesticides, were chosen for their approved toxic environmental effect, while 2,2'-bipyridine was selected for comparison, because of its powerful metal complexing ability. Chromium(III) is the toxic heavy metal ion that forms numerous stable complex compounds. The heterogeneity and complexity of natural matrices justify the usage of model systems such these, with the aim of evaluation of complex processes in the environment. 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 N-donor atoms in the investigated ligands. UV/Vis data describing chromium interaction with ligands is placed in correlation with ESI-MS data on the complexes. UV/Vis spectroscopy and ESI-MS quantification showed a large difference in the information they give in describing the interaction of chromium(III) with the ligands, the ESI-MS technique being superior. 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.