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- Iron specification in bathing waters using sequential labe-on-valve (si-Lov) solid-phase spectrophotometryPublication . Suárez, Ruth; Rangel, Maria; Bordalo, Adriano A.; Cerdà, Víctor; Rangel, António O. S. S.; Mesquita, Raquel B. R.
- Spectrofluorimetric determination of iodide in urine samples without pretreatment using a miniaturized analyzer chip in a multi-syringe flow systemPublication . Miranda, Joana L. A.; Mesquita, Raquel B. R.; Estrela, José M.; Cerdà, Victor M.; Palacio, Edwin; Rangel, António O. S. S.
- 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%).
- Sequential injection system with in-line solid phase extraction and soil minicolumn for determination of zinc and copper in soil leachatesPublication . Paluch, Justyna; Mesquita, Raquel B. R.; Cerdà, Victor; Kozak, Joanna; Wieczorek, Marcin; Rangel, António O. S. S.A sequential injection (SI) system equipped with in-line solid phase extraction column and in-line soil minicolumn is proposed for determination of zinc and copper in soil leachates. The spectrophotometric determination (560 nm) is based on the reaction of both analytes with 1-(2-Pyridylazo)-2-naphthol (PAN). Zinc is determined after retaining copper on a cationic resin (Chelex100) whereas copper is determined from the difference of the absorbance measured for both analytes, introduced into the system with the use of a different channel, and zinc absorbance. The influence of several potential interferences was studied. Using the developed method, zinc and copper were determined within the concentration ranges of 0.005–0.300 and 0.011–0.200 mg L−1, and with a relative standard deviation lower than 6.0% and 5.1%, respectively. The detection limits are 1.4 and 3.0 μg/L for determination of zinc and copper, respectively. The developed SI method was verified by the determination of both analytes in synthetic and certified reference materials of water samples, and applied to the determination of the analytes in rain water and soil leachates from laboratory scale soil core column and in-line soil mini-column.
- Exploiting the use of 3,4-HP Oligands as non toxic reagents for the determination of iron in natural waters with a sequential injection approachPublication . Mesquita, Raquel B. R.; Suárez, Ruth; Cerdà, Víctor; Rangel, Maria; Rangel, António O.S.S.In this paper, the use of 3-hydroxy-4-pyridinone (3,4-HPO) chelators as nontoxic chromogenic reagents for iron determination is proposed. The potential application of these compounds was studied in a sequential injection system. The 3,4-HPO ligands used in this work were specially designed to complex iron(III) at physiologic pH for clinical applications. The developed sequential injection method enabled to study the reaction conditions, such as buffering and interferences. Then, to further improve the low consumption levels, a microsequential injection method was developed and effectively applied to iron determination in bathing waters using 3,4-HPO ligands. The formed iron complex has a maximum absorbance at 460 nm. The advantage of using minimal consumption values associated with sequential injection, together with the lack of toxicity of 3,4-HPO ligands, enabled to present a greener chemistry approach for iron determination in environmental samples within the range 0.10-2.00 mg Fe/L with a LOD of 7 mu g/L. The overall effluent production was 350 mu L corresponding to the consumption of 0.48 mg of 3,4-HPO ligand, 0.11 mg of NaHCO3, 0.16 mg of HNO3 and 50 mu L. of sample. Three reference samples were assessed for accuracy studies and a relative deviation < 5% was obtained. The results obtained for the assessment of iron in inland bathing waters were statistically comparable to those obtained by the reference procedure.
- Iron speciation by microsequential injection solid phase spectrometry using 3-hydroxy-1(H)-2-methyl-4-pyridinone as chromogenic reagentPublication . 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%).
- Green analytical automatic method for iron speciation in bathing water samplesPublication . Suárez, Ruth; Mesquita, Raquel B. R.; Rangel, M.; Bordalo, Adriano A.; Cerdà, Victor; Rangel, António O. S. S.
- A miniaturized chip in a multi-syringe flow system for spectrofluorimetric determination of iodide in urine samplesPublication . Miranda, Joana L. A.; Palacio, Edwin; Mesquita, Raquel B. R.; Estela, José M.; Cerdà, Víctor; Rangel, António O. S. S.
- Micro-SI system for the spectrophotometric bi-parametric determination of iron and copper in soil leachatesPublication . González, Alba; Mesquita, Raquel B. R.; Avivar, Jessica; Moniz, Tânia; Rangel, Maria; Cerdà, Victor; Rangel, António O. S. S.