Speciation of metal–EDTA complexes by flow injection analysis with electrospray ionization mass spectrometry and ion chromatography with inductively coupled plasma mass spectrometry

Abstract

Original PaperSpeciation of metal-EDTA complexes by flow injection analysis with electrospray ionization mass spectrometry and ion chromatography with inductively coupled plasma mass spectrometry Flow injection analysis (FIA) with ESI-MS and ion chromatography (IC) with inductively coupled plasma-MS (ICP-MS) and their MS spectral showed that these metal -EDTA complexes were present in solution. Based on the ESI-MS, ion chromatographic separation and ICP-MS detection of these complexes are possible because IC-ICP-MS requires stable metal -EDTA complex during the chromatographic separation. The separation of these metal -EDTA complexes was achieved on an anion-exchange column with a mobile phase containing 30 mM NH 4 (HPO 4 ) 2 at pH 7.5 within 7 min with ICP-MS providing element specific detection. The ICP-MS LODs for the metal -EDTA were in the range of 0.1 -0.5 lg/L with the exception of Fe (15 lg/L). The proposed method was a simple procedure for sample processing, using direct injection of sample without removal of sample matrix and was successfully applied to the determination of metal -EDTA complexes in real samples. IntroductionEDTA is a chelating agent which has the potential to perturb the natural speciation of metals, to influence metal bioavailability [1], and to remobilize metals from sediments and aquifers [2]. Chelating agents occur in natural waters predominantly as metal complexes. There are many studies emphasizing the importance of chelation on metal bioavailability, plant uptake, toxicity, transport, adsorption, distribution, and fate [3]. However, the identification and detection of these metal complexes in environmental sample is still a significant analytical challenge because of their structural similarities and presence at low concentrations in environmental matrices [4]. Separation of these complexes is therefore an important step in the development of an analytical method suitable for the detection of metal -EDTA complexes in environmental samples.CE and ion chromatography (IC) are the main separation methods used for the determination of metal -aminopolycarboxylic complexes. Using the CE approach, metal complexes with nitrilotriacetic acid (NTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), EDTA, and diethylenetriaminepentaacetic acid (DTPA) were all successfully separated using either CZE [5 -7] or MEKC [8] with UV detection. LODs of 2 -500 lM were obtained using these CE methods, which are usually not sensitive enough for the analysis of trace levels of these complexes in environmental samples. As an alternative to CE, IC is often used to determine metal -EDTA complexes, based on the precolumn complexation of the chelating agents with metals. The separation of these complexes by ionpairing [9 -12] and ion-exchange chromatography [13 -15] has been accomplished with conductivity or UV/Visible detection, but these detectors are nonselective and it is therefore often impossible to identify all metal -EDTA complexes in complex matrices. To address these problems, the separation...

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). …”

“…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.…”

Detection of trace levels of lead in aqueous liquids using extractive electrospray ionization tandem mass spectrometry

“…2 showed the amplified view of the MS spectral region between m/z 490 and 500. The intensity ratio of peaks at m/z 497, 496, and 495 was 1:0.49:0.60, which approximately agreed with the lead natural isotopic ratio (1:0.42:0.46) although our experimental values were higher than the theoretical estimate [61]. In addition, we found that the peak at m/z 493 was not very stable especially when analyzing complex samples, and an example of a high peak collected in our experiments was shown in Fig.…”

“…Although further studies are necessary, one of the possible reasons for the isotopic ratio difference is that EESI has a different ionization mechanism than that of ESI. The isotopic ratio in this study was measured in the liquid phase by EESI where solvent-dependent extractive process plays an important role [59], while the previous study was conducted by ESI in the gas phase [61]. The peak at m/z 497 was tentatively assigned to [EDTAþ 208 Pb-3H] À .…”