Loading...
3 results
Search Results
Now showing 1 - 3 of 3
- Iodine speciation in coastal and inland bathing waters and seaweeds extracts using a sequential injection standard addition flow-batch methodPublication . Santos, Inês C.; Mesquita, Raquel B. R.; Bordalo, Adriano A.; Rangel, António O. S. S.The present work describes the development of a sequential injection standard addition method for iodine speciation in bathing waters and seaweeds extracts without prior sample treatment. Iodine speciation was obtained by assessing the iodide and iodate content, the two inorganic forms of iodine in waters. For the determination of iodide, an iodide ion selective electrode (ISE) was used. The indirect determination of iodate was based on the spectrophotometric determination of nitrite (Griess reaction). For the iodate measurement, a mixing chamber was employed (flow batch approach) to explore the inherent efficient mixing, essential for the indirect determination of iodate. The application of the standard addition method enabled detection limits of 0.14 µM for iodide and 0.02 µM for iodate, together with the direct introduction of the target water samples, coastal and inland bathing waters. The results obtained were in agreement with those obtained by ICP-MS and a colorimetric reference procedure. Recovery tests also confirmed the accuracy of the developed method which was effectively applied to bathing waters and seaweed extracts.
- Use of solid phase extraction for the sequential injection determination of alkaline phosphatase activity in dynamic water systemsPublication . Santos, Inês C.; Mesquita, Raquel B.R.; Bordalo, Adriano A.; Rangel, António O.S.S.In this work, a solid phase extraction sequential injection methodology for the determination of alkaline phosphatase activity in dynamic water systems was developed. The determination of the enzymatic activity was based on the spectrophotometric detection of a coloured product, p-nitrophenol, at 405 nm. The p-nitrophenol is the product of the catalytic decomposition of p-nitrophenyl phosphate, a noncoloured substrate. Considering the low levels expected in natural waters and exploiting the fact of alkaline phosphatase being a metalloprotein, the enzyme was pre-concentrated in-line using a NTA Superflow resin charged with Zn2þ ions. The developed sequential injection method enabled a quantification range of 0.044–0.441 unit mL 1 of enzyme activity with a detection limit of 0.0082 unit mL 1 enzyme activity (1.9 mmol L 1 of pNP) and a determination rate of 17 h 1. Recovery tests confirmed the accuracy of the developed sequential injection method and it was effectively applied to different natural waters and to plant root extracts.
- Screening of cadmium and lead in potentially contaminated waters using a spectrophotometric sequential injection lab-on-valve methodologyPublication . Santos, Inês C.; Mesquita, Raquel B. R.; Rangel, António O. S. S.The present work describes the development of a µSI-LOV method for the simultaneous screening of cadmium and lead in potentially contaminated water samples. To attain the biparametric determination, dithizone was chosen as the spectrophotometric reagent as it forms a colored complex with both metal ions, at different pH conditions. The cadmium determination was attained in strong alkaline conditions (pH≈12); the lead determination was calculated by the difference with the determination of both metals in mild alkaline conditions (pH≈8). The colored complex was measured at 550 nm and the method presented a LOD of 34 μg L−1 for cadmium and 56 μg L−1 for lead, with a sample consumption of 20 µL per assay and a determination rate of 55 h−1. The results obtained were in agreement with those obtained by FAAS. The developed method was efficiently applied to the screening of cadmium and lead in marine port waters.