Evaluation of electrospray ionisation mass spectrometry as a technique for the investigation of competitive interactions: A case study of the ternary Th‐Mn‐EDTA system

Abstract

This study showed the complexity of quantifying a ternary system involving different co-existing species. Nonetheless, the step-wise protocol developed provided quantitative data on the displacement of Mn from its EDTA complex by Th.

Fe- and Cu-Complex Formation with Artificial Ligands Investigated by Ultra-High Resolution Fourier-Transform ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS): Implications for Natural Metal-Organic Complex Studies

“…Overall, our findings agreed well with those from other studies and the predictions from the speciation models: Most EDTA-compounds described by previous reports including uncomplexed EDTA and metal-EDTA were detected in this study as well as predicted by the PHREEQC calculations ( Table 3, Chen et al, 2008;Reinoso-Maset et al, 2012). In addition, mostly monomers, and only two dimers were detected, indicating that metal-EDTA equilibrium studies are likely to be comparable amongst different experimental and instrumental setups.…”

“…Both Cu(I) and Cu(II) were involved in the 1:1 complex formation with SA, while Fe was bound as Fe(III) ( Table 5). Chen et al (2008) and # described by Reinoso-Maset et al (2012). …”

“…The additional input of sodium to the citrate and EDTA setups for pH adjustment did not enhance the ionization of sodiated species further, but had an opposite effect, with speciation changing drastically (Tables 2, 3, Figure 4) together with an overall sharp decrease in relative signal intensities of all (free and complexed) target compounds (Figure 1). Reinoso-Maset et al (2012) demonstrated in their ESI-MS study on Mn-EDTA and Th-EDTA complexes, that ion suppression of EDTA occurred in negative mode as soon as metals salts were added, both through the salt additives Cl − or NO − 3 , as well as the metal ions themselves, and that signal intensities of target metal-ligand complexes could decrease up FIGURE 3 | Relationship between molecular weight and signal intensity for samples prepared with a methanol:water matrix. Each point in the correlation plot is the calculated average m/z and average signal intensity of a compound group at a specific setting (e.g., all free citrate ligands in samples with aq.…”

“…All of the above mentioned issues have been known for a while (Di Marco and Bombi, 2006), but only in recent years, systematic, and compound-specific investigations have been increasingly used to evaluate ESI-MS as a quantitative tool in metal-ligand equilibrium studies (Gledhill, 2001;Rellán-Álvarez et al, 2008;Keith-Roach, 2010;Reinoso-Maset et al, 2012). In this study, we aim to address the above mentioned analytical challenges, and report the applicability of ultra-high resolution ESI-FT-ICR-MS for the qualitative and quantitative investigation of metal-ligand equilibria.…”

“…EDTA, an artificial ligand produced for industrial and pharmaceutical applications, has gained recent interest due to its accumulation in the aquatic environment, where it impacts trace metal mobility (Nowack, 2002). It is a hexadentate ligand with two amine and four carboxylate functional groups and forms strong 1:1 or 1:2 complexes with transition metals and other cations (Chen et al, 2008;Reinoso-Maset et al, 2012). 1-nitroso-2-naphthol (hereafter referred to as NN) is a hydrophobic metal chelator with a nitroso-and a hydroxyl group.…”