In 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.
- Iodine
- Iron
- Flow based systems
- 3,4–hydroxypyridinone ligands
- Food and biological samples
- Doutoramento em Biotecnologia
Flow-based methods for iodine and iron quantification in food-related, water, and blood serum samples
Miranda, J. L. A. (Student). 6 Jun 2022
Student thesis: Doctoral Thesis