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- 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 watersPublication . Mesquita, Raquel; Moniz, Tânia; Miranda, Joana L. A.; Gomes, Vânia; Silva, André M. N.; Rodriguez-Borges, J. E.; Rangel, António O. S. S.; Rangel, MariaThe 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.
- Effect of tris(3-hydroxy-4-pyridinonate) iron(III) complexes on iron uptake and storage in soybean (Glycine max L.)Publication . Santos, Carla S.; Carvalho, Susana M.P.; Leite, Andreia; Moniz, Tânia; Roriz, Mariana; Rangel, António O. S. S.; Rangel, Maria; Vasconcelos, Marta W.Iron deficiency chlorosis (IDC) is a serious environmental problem affecting the growth of several crops in the world. The application of synthetic Fe(III) chelates is still one of the most common measures to correct IDC and the search for more effective Fe chelates remains an important issue. Herein, we propose a tris(3-hydroxy-4-pyridinonate) iron(III) complex, Fe(mpp)3, as an IDC corrector. Different morphological, biochemical and molecular parameters were assessed as a first step towards understanding its mode of action, compared with that of the commercial fertilizer FeEDDHA. Plants treated with the pyridinone iron(III) complexes were significantly greener and had increased biomass. The total Fe content was measured using ICP-OES and plants treated with pyridinone complexes accumulated about 50% more Fe than those treated with the commercial chelate. In particular, plants supplied with compound Fe(mpp)3 were able to translocate iron from the roots to the shoots and did not elicit the expression of the Fe-stress related genes FRO2 and IRT1. These results suggest that 3,4-HPO iron(III) chelates could be a potential new class of plant fertilizing agents.
- Microsequential injection lab-on-valve system for the spectrophotometric bi-parametric determination of iron and copper in natural watersPublication . González, Alba; Mesquita, Raquel B. R.; Avivar, Jessica; Moniz, Tânia; Rangel, Maria; Cerdà, Víctor; Rangel, António O. S. S.The determination of iron and copper exploiting a microsequential injection lab-on-valve system with online spectrophotometric detection is described. A new, environmental friendly 3-hydroxy-4-pyridinone chelator, functionalized with a polyethylene glycol chain (MRB12) to improve water solubility, was used for iron determination. For copper determination, 1-(2-pyridylazo)-2-naphthol (PAN) was used. Different parameters affecting the formation of the complexes were studied, namely sample volume, reagent concentration, and buffer composition and concentration. The optimized conditions, 150 mu L of sample volume and 250 mg L-1 of MRB12 for iron determination, and 200 mu L of sample and 120 mg L-1 of PAN for copper determination, enabled an LOD of 15 and 18 mu g L-1 for iron and copper, respectively. The robustness of the developed procedure was assessed by the calculation of the relative standard deviation (RSD), 5% for iron determination and 2% for copper determination. The accuracy of the method was assessed comparing the results with two certified samples (RD < 7.5%) and calculating recovery percentages with five river water samples (average < 107%).