New insights in the slow ligand exchange reaction between Cr(III)-EDTA and Fe(III), and direct analysis of free and complexed EDTA in tannery wastewaters by liquid chromatography - Tandem mass spectrometry

Thionine-mediated electrocatalytic reduction for electrochemical detection of EDTA-Fe(III) in soy sauce

Electrocatalytic reactions based on electron transfer mediators provide a simple and effective route for the development of convenient and sensitive electrochemical assays. Here, we report a novel electrocatalytic assay for detection of EDTA-Fe(III), which is widely used as a supplement in iron-fortified foods to reduce prevalence of iron deficiency. Unlike conventional electrochemical methods to detect Fe(III) ion, signaling mechanism of our electrocatalytic assay relies on the previously unexplored thionine-mediated electrochemical reduction of EDTA-Fe(III). This electrocatalytic detection method is sensitive for EDTA-Fe(III) detection in the linear concentration range from 10 to 750 μM with a detection limit of 2.5 μM. It is also specific enough and applicable to detection of EDTA-Fe(III) in real soy sauce samples with satisfactory recovery. The one-step electrocatalytic reduction for signal generation enables the direct and sensitive electrochemical detection of EDTA-Fe(III). We believe that this electrocatalytic assay can serve as a general platform for quantification of EDTA-Fe(III) in many EDTA-Fe(III)-fortified foods. And because thionine is increasingly used as a signal reporter in electrochemical DNA/aptamer sensors, the engineered electrocatalytic reaction of thionine-mediated electrochemical reduction of EDTA-Fe(III) will also provide a simple signal amplification means for the development of highly sensitive electrochemical biosensors.

Fast Determination of a Novel Iron Chelate Prototype Used as a Fertilizer by Liquid Chromatography Coupled to a Diode Array Detector

The environmental risk of the application of synthetic chelates has favored the implementation of new biodegradable ligands to correct Fe-deficient plants. This study developed and validated an analytical method for determination of a new prototype iron chelate─Fe(III)-benzeneacetate, 2-hydroxy-α-[(2-hydroxyethyl)amino]─(BHH/Fe³⁺) based on liquid chromatography with diode array detection, as a potential sustainable alternative. Chromatographic analysis was performed on a LiChrospher RP-18 in reverse-phase mode, with a mobile phase consisting of a mixture of acetonitrile (solvent A) and sodium borate buffer 0.20 mM at pH = 8 (solvent B) at a flow rate of 1.0 mL/min in isocratic elution mode. This method was fully validated and found to be linear from the limit of quantification (LOQ) to 50 mg/L and precise (standard deviation below 5%). The proposed method was demonstrated to be selective, precise, and robust. The developed methodology indicated that it is suitable for the quantification of iron chelate BHH/Fe³⁺.