Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- 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.
- Flow-based methods for iodine and iron quantification in food-related, water, and blood serum samplesPublication . Miranda, Joana Lopes Abreu; Rangel, António Osmaro Santos Silva; Mesquita, Raquel Beatriz Ribeiro deIn this thesis, the use of different flow systems was exploited for developing new methodologies for miniaturization of the analysis of complex matrix samples (food-related, water and biological samples). The main purpose was to devise methodologies able to perform in-line the necessary sample treatment operations, reducing the operator influence and reagents manipulation, and tentatively using greener processes. Under this program, a flow-based spectrofluorimetric chip manifold method for the iodine determination in food-related samples, was developed. The use of a multi-syringe enabled the automation of the Sandell-Kolthoff reaction, leading to a lower operator influence and reagents consumption and manipulation. An in-line oxidation process was implemented to analyse samples with organo-iodine containing compounds; this implied to eliminate interferences and decomposition of organo-iodine compounds in supplement pills and seaweed samples (Chapter 3). The developed method was effectively applied to the iodine determination in salt, food supplements (algae), seaweed and pharmaceutical samples, which are examples of intake forms of iodine. The proposed manifold, combined with the fluorometric reaction, made this method more sensitive than the classic approach of the Sandell-Kolthoff reaction and presents some advantageous over previously described flow methods, namely in terms of a wider dynamic concentration range. The method allowed to determine iodine within a range of 0.20 – 4.0 µmol/L, with or without the in-line UV digestion, with a limit of detection of 0.028 µmol/L and 0.025 µmol/L, respectively. In Chapter 4, an hexadentate 3-hydroxy-4-pyridinone (3,4–HPO) ligand was used as a chromogenic reagent for the spectrophotometric quantification of iron(III) in fresh and sea waters. A method based on a micro sequential injection lab-on-valve (µSI-LOV) system in a solid phase spectrometry (SPS) mode, is described. To implement SPS, a packed column of nitrilotriacetic acid superflow resin (NTA) in the flow cell, was used, consequently eliminating the sample matrix. Furthermore, the possibility to perform of an analytical curve resorting to just one standard was demonstrated. The consumption of the hexadentate 3,4–HPO ligand was about 30 µg per determination and the effluent production lower than 2.5 mL. The dynamic concentration range was 0.45 – 9.0 µmol/L, with a limit of detection of 0.13 µmol/L and limit of quantification 0.43 µmol/L. The proposed µSI-LOV-SPS methodology was successfully applied to river, ground, estuarine, tap, and sea waters. The evaluation of the analytical performance of different 3,4–HPO bidentate chelators, as chromogenic reagents in the determination of iron(III), using a µSI system, in aqueous samples, was described in Chapter 5. In Chapter 6, a bidentate 3-hydroxy-4-pyridinone ligand was anchored to sepharose beads and used as chromogenic reagent for the spectrophotometric quantification of non-transferrin-bound iron (NTBI). By employing a micro sequential injection lab-on-valve (µSI-LOV) system with a SPS technique, it was possible to eliminate the interference of the sample matrix and quantify iron(III) directly on the beads surface. The dynamic concentration range was 1.62 – 7.16 µmol/L, with a limit of detection of 0.49 µmol/L and limit of quantification 1.62 µmol/L. The proposed µSI-LOV-SPS method, in Chapter 6, was a contribution to the development of an automated method for the quantification of the NTBI in serum samples.
- New hydrophilic 3-hydroxy-4-pyridinone chelators with ether-derived substituents: synthesis and evaluation of analytical performance in the determination of iron in watersPublication . Moniz, Tânia; Cunha-Silva, Luís; Mesquita, Raquel B.R.; Miranda, Joana L.A.; Silva, André M.N.; Silva, Ana M.G.; Rangel, António O.S.S.; Castro, Baltazar de; Rangel, MariaThree new hydrophilic 3-hydroxy-4-pyridinone chelators containing ether-derived substituents were prepared by a more sustainable synthetic protocol that involves the use of microwave heating and commercially available amines, allowing the successful production of highly water soluble chelators with improved reaction yields and reaction times. Compared with parent 3-hydroxy-4-pyridinone ligands, the new compounds were obtained faster and in higher amounts, facilitating the scale up of the synthesis, which is crucial to produce these ligands and their respective iron(III) complexes for many biological, analytical and agricultural applications. Ligands were fully characterized by 1H and 13C Nuclear Magnetic Resonance, High Resolution Mass Spectrometry and Single Crystal X-Ray Diffraction and their performance in the analytical determination of iron(III) in water samples was evaluated by sequential injection methods. The results obtained are scientifically relevant, pointing out the potential of the new and straightforwardly synthesized ligands as analytical reagents for determination of iron(III).
- Iron speciation in natural waters by sequential injection analysis with a hexadentate 3-hydroxy-4-pyridinone chelator as chromogenic agentPublication . 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.
- Development of a sequential injection methodology for iron speciation in waters using an hexadentate 3,4 – hydroxypiridinone chelatorPublication . Miranda, Joana L. A.; Mesquita, Raquel B. R.; Rangel, Maria; Rangel, António O. S. S.