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Iron speciation in natural waters by sequential injection analysis with a hexadentate 3-hydroxy-4-pyridinone chelator as chromogenic agent

Publication . Miranda, Joana; Mesquita, Raquel; Ana, Nunes; Rangel, Maria; Rangel, António O. S. S.

A sequential injection method for iron speciation in various types of natural waters was developed using a synthesised hexadentate 3-hydroxy-4-pyridinone chelator (CP256). The denticity of the ligand that allow formation of the corresponding iron (III) complex in a 1:1 stoichiometry proved to be highly advantageous, in comparison with parent bidentate, hydroxy-4-piridinone chelators, with a two fold increase of reaction sensitivity and over 65% decrease of the LOD. A solid phase extraction approach was employed to attain matrix elimination, facilitating iron (III) determination and application to high salinity waters. The combination with the total iron determination obtained by the direct reaction of the ligand resulted in iron speciation. Two detection spectrophotometric cells were tested, a conventional flow cell (CFC) and a liquid waveguide capillary cell (LWCC). The dynamic concentration ranges were 0.1–2 mg/L with the CFC detection and 0.005–0.1mg/L with the LWCC, with limit of detection of 30 mg/L and 6 mg/L, respectively. The developed method was successfully applied to a variety of natural waters.

2016Journal article

Open access

Synthesis and characterization of a 3-hydroxy-4-pyridinone chelator functionalized with a polyethylene glycol (PEG) chain aimed at sequential injection determination of iron in natural waters

Publication . Mesquita, Raquel; Moniz, Tânia; Miranda, Joana L. A.; Gomes, Vânia; Silva, André M. N.; Rodriguez-Borges, J. E.; Rangel, António O. S. S.; Rangel, Maria

The synthesis of a highly water soluble 3-hydroxy-4-pyridinone ligand, functionalized with a hydrophilic ethylene glycol chain (PEG-HPO), was successfully achieved and is reported together with that of its iron (III) complex. The improved hydrophilicity of both the PEGylated 3,4-HPO ligand and its iron(III) complex were fully investigated in an analytical application and, the new chelator is proposed for the spectrophotometric sequential injection determination of iron in waters. The new ligand provided better sensitivity and a lower LOD for iron determination than that obtained for N-alkyl-3-hydroxy-4-pyridinone ligands. The developed sequential injection method presents a dynamic working range of 0.10-1.00 mg Fell. with a LOD of 48 mu g/L. Due to the use of a sequential injection system, the overall effluent production was <2 mL corresponding to the consumption of 44 mu g of PEG-HPO, 0.71 mg of NaHCO3, 0.92 mg of HNO3 and 500 mu L of sample. Two reference samples were assessed for accuracy studies and a relative deviation <5% was obtained; eight waters samples were analyzed and the results compared with the reference procedure, and no statistical difference was observed for the two sets of results.

2015Journal article

Restricted access

Iron speciation by microsequential injection solid phase spectrometry using 3-hydroxy-1(H)-2-methyl-4-pyridinone as chromogenic reagent

Publication . Suárez, Ruth; Mesquita, Raquel B. R.; Rangel, Maria; Cerdà, Víctor; Rangel, António O.S.S.

The speciation of iron using the newly synthesized 3-hydroxy-1(H)-2-methyl-4-pyridinone by solid phase spectrophotometry in a microsequential injection lab-on-valve (µSI-LOV-SPS) methodology is described. Iron was retained in a reusable column, Nitrilotriacetic Acid Superflow (NTA) resin, and the ligand was used as both chromogenic and eluting reagent. This approach, analyte retention and matrix removal, enabled the assessment of iron (III) and total iron content in fresh waters and high salinity coastal waters with direct sample introduction, in the range of 20.0–100 µg/L. with a LOD of 9 µg/L. The overall effluent production was 2 mL, corresponding to the consumption of 0.48 µg of 2-metil-3-hydroxy-4-pyridinone, 0.34 mg of NaHCO3, 16 mg of HNO3, 4.4 µg H2O2 and 400 µL of sample. Four reference samples were analyzed and a relative deviation<10% was obtained; furthermore, several bathing waters (♯13) were analyzed using the developed method and the results were comparable to those obtained by atomic absorption spectrophotometry (relative deviations<6%).

2015Journal article

Open access

Flow analysis approaches to handle saline samples

Publication . Rangel, António O. S. S.

2014Conference object

Open access

Contributions to separation processes for sample treatment in flow analysis

Publication . Rangel, António O. S. S.

2014Conference object

Open access