Extraction-liquid chromatography with electrochemical and spectrophotometric detection for the determination of copper and iron in biological and river water samples

Advances in the determination of trace amounts of iron cations through electrochemical methods: A comprehensive review of principles and their limits of detection

Quantification of trace amounts of iron is of great importance in various fields. In the industrial sector, it is crucial to monitor the release of iron out of corrosion, pickling treatment, and steel manufacturing to address potential environmental and economic challenges. In biological systems, despite its indispensability, it is essential to maintain iron concentration below a specific threshold. Electrochemical (EC) methods provide significant analytical capabilities due to their simplicity, ease of use, and cost-effectiveness. This review focuses on the fundamental principles of EC methods for iron detection, including potentiometry, amperometry, coulometry, voltammetry, and electrochemical impedance spectroscopy (EIS). It further explains the process of obtaining calibration curves, and subsequently, determining the concentration of unknown ions. Additionally, technical notes are presented on selecting the initial signal value, reducing the duration of tests, excluding non-faradaic signals, and extending the linear region with the lowest detection limit. These notes are supported by key findings from relevant case studies.

Trace determination of iron in water at the microgram/l level by on-line coupling of capillary isotachophoresis and capillary zone electrophoresis with UV detection of the EDTA-Fe (III) complex

The determination of iron in water at the trace level by on-line coupled capillary isotachophoresis and capillary zone electrophoresis (CITP-CZE) with a commercial column coupling device is described. Iron is determined as the negatively charged complex with EDTA which is highly UV-absorbing and thus enables photometric detection at 254 nm. The analyses are performed using 10 mmol/l HCl + 20 mmol/l L-histidine + 0.1% hydroxypropylmethyl cellulose (pH 6.0), 5 mmol/l MES, and 25 mmol/l MES + 10 mmol/l bis-tris-propane (pH 6.6) which served as leading, terminating and background electrolyte, respectively. Samples are acidified with HNO3, diluted and EDTA added (to a final concentration of 10(-4) mol/l) prior to CITP-CZE analysis. The detection limit of Fe(III) is 10 micrograms/l, and is given by the chemical noise due to the impurities of the chemicals used enriched by the ITP preconcentration step. The precision of the CE measurement, expressed by the relative standard deviation, is about 3% (at the 400 micrograms/l level); the recovery is between 80 and 115% depending on the iron concentration level (40-400 micrograms/l).