The environmental behavior of iron, as well as its uptake by plants, its absorption by human and animals and its storage and transport all depend on its oxidation state, making redox speciation analysis of this element very important.
Iron speciation in soil and other matrices using speciated isotope dilution according to US EPA 6800
An ion chromatography–inductively coupled plasma mass spectrometry (IC-ICP/MS) technique was developed in this analysis to determine Fe (II) and Fe (III) based on in-column complexation by pyridine-2,6-dicarboxylic acid, commonly called dipicolinic acid (DPA). DPA is an established chelator for trivalent and divalent metal ions including those of iron.
A remote signal was used to synchronize the IC and ICP/MS instruments. The Agilent MassHunter software was used to perform data handling and manipulation, while the sample loading and gradient program were controlled by the MagIC Net software. The chromatographic condition achieved baseline separation between Fe (III) and Fe (II) in less than 5 minutes, as indicated in Figure 1.
Figure 1. Chromatogram of a standard solution containing 250.0 ng/g of Fe(II) and Fe(III) (conditions as Figure 1).
Analysis of several beverage samples and aqueous standard solutions was carried out. In the majority of samples, Fe (II) was the most dominant species, as shown in Figure 2. Depending on various environmental conditions, iron is constantly interconverting between the +2 and +3 oxidation states, that is, Fe (II) and Fe (III). This technique enables precise quantitation of each species in soil, water, wastewater, and nutraceuticals.
Figure 2. Calibration curve (0.01–500 ppb). Column: Metrosep A Supp 10 S-Guard/4.0; eluent: 4.0 mmol/L DPA, 20 mmol/L ammonium nitrate (pH 4.3); flow rate: 0.8 mL/min, isocratic; m/z 56
Iron – further applications with IC-ICP/MS
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