Loading...
2 results
Search Results
Now showing 1 - 2 of 2
- Membrane-based separation in flow analysis for environmental and food applicationsPublication . Santos, Inês C.; Mesquita, Raquel B. R.; Rangel, António O. S. S.Membrane-based separation techniques have been used as an efficient process for analyte separation or enrichment and matrix removal. By coupling these techniques to flow-based analysis, sample preparation and analyte detection can be automated and miniaturized. Different membrane separation techniques are available but the most used in flow analysis are gas diffusion, dialysis, supported liquid membranes and polymer inclusion membranes. The current state of the art of membrane-based separations hyphenated with flow techniques is presented along with a discussion of the applications to environmental and food analysis. Moreover, a brief description of gas diffusion, dialysis and membrane extraction techniques is also included.
- Application of mid- and near-infrared spectroscopy for the control and chemical evaluation of brine solutions and traditional sea saltsPublication . Galvis-Sánchez, Andrea C.; Santos, Inês C.; Mesquita, Raquel B. R.; Lopes, João A.; Rangel, António O. S. S.; Delgadillo, IvonneMid- and near-infrared spectroscopy methodologies were explored for the analysis of brine solutions and traditional sea salt samples. Brine solutions from different salt pans, corresponding to different stages of sodium chloride crystallisation, were collected. A total of 61 dried and non-dried traditional sea salts were also analysed. Partial least squares regression with leave-one-out cross-validation strategy was applied for the calibration of inorganic constituents Ca2+, Mg2+ and K+, alkalinity as HCO (3) (-) , SO (4) (2-) , NO (2) (-) and NO (3) (-) and phosphate in brine solutions. Promising results were obtained with the near-infrared (NIR) methodology for brine solutions with coefficients of determination R (2) > 0.90 for Mg+2, K+, HCO (3) (-) and SO (4) (2-) . Using mid-infrared, the calibration for H2PO (4) (-) was R (2) = 0.85. In relation to the sea salt samples, the strategy adopted was the re-sampling based cross-validation using different spectral pre-processing treatments. In this case, the calibrations using the two IR methodologies fell bellow acceptable levels for the techniques; however, by comparing the R (2) coefficient, the results were slightly better when using the NIR spectra of dried sea samples. In general, these results open a new possibility for the IR applications and also bring an opportunity for continuing with the NIR characterization for dried sea salt samples.