Development of a sequential injection system for the determination of nitrite and nitrate in waters with different salinity: Application to estuaries in NW Portugal

In this work, a sequential injection methodology for monitoring nitrite and nitrate in estuarine waters without any previous treatment is described. The developed system was applied to the measurement of nitrite and nitrate in estuarine waters of three rivers in the NW Portugal, allowing an automatic, fast (ca 60 h 1) and precise method (relative standard deviation lower than 2%). The procedure was based on the reaction between nitrite, sulfanilamide and N-(1-naphthyl)-ethylenediamine dihydrochloride (N1NED), whereas the determination of nitrate resulted from its reduction to nitrite, using an in-line cadmium column, followed by the same reaction. The samples were collected in three locations for each river (Douro, C avado and Ave) covering the lower, middle and upper section of the estuaries. Despite the presence of a salinity gradient, this parameter showed no interference in the accuracy of the determinations. The results obtained for the described method for nitrite were statistically comparable to those obtained by the reference procedure. For the determination of nitrate, recovery tests confirmed that the sequential injection methodology provided good quality results.info:eu-repo/semantics/publishedVersio

Sequential injection system exploring the standard addition method for phosphate determination in high salinity samples: interstitial, transitional and coastal waters

Technical NoteA sequential injection system for phosphate determination within a wide concentration range was developed for water samples with high salinity levels. The determination is based on molybdenum blue chemistry using the standard addition quantification method. The detection system included a multireflective flow cell coupled to a light emitting diode, enabling the minimization of the schlieren effect. The developed system gave a LOD of 0.3 mmol P L 1 and LOQ of 1.1 mmol P L 1 with a sample consumption of 125 mL. A determination rate of about 30 h 1 was obtained, and the developed method was effectively applied to interstitial, transitional and coastal waters.info:eu-repo/semantics/publishedVersio

Development of a sequential injection gas diffusion system for the determination of ammonium in transitional and coastal waters

This work describes the development of a sequential injection system for the ammonium determination in transitional and coastal waters with a wide salinity range. Estuarine waters are rather complex matrices as their characteristics change considerably along the salinity gradient, as well as the ammonium levels. The developed system effectively solves these issues by converting ammonium into ammonia and using a gas diffusion unit (GDU) for matrix removal. The ammonium determination in a wide quantification range (0.1–5.0 mg L−1) was obtained with small changes in the protocol sequence and was applied, not only to estuarine samples, but also well water samples (low salinity) and coastal waters (higher salinity). Spectrophotometry was the chosen detection system to measure the absorbance change in the bromothymol blue acid base indicator caused by the diffusion of ammonia through the GDU. Additionally, the developed system used a green chemistry approach, as there was no indicator reagent consumption per determination, still maintaining a good precision (relative standard deviation lower than 2%) and a low detection limit, 27 μg L−1 (1.5 μM).info:eu-repo/semantics/acceptedVersio

Persistent and emerging pollutants assessment on aquaculture oysters (Crassostrea gigas) from NW Portuguese coast (Ria De Aveiro)

The study aim was to determine a range of relevant persistent and emerging pollutants in oysters produced in an aquaculture facility located in an important production area, to assure their safety for human consumption. Pollutants, including 16 PAHs, 3 butyltins (BTs), 29 flame retardants (FRs, including organophosphate and halogenated FRs), 35 pesticides (including 9 pyrethroid insecticides) and 13 personal care products (PCPs, including musks and UV filters), were determined in oysters' tissues collected during one year in four seasonal sampling surveys. The seasonal environmental pollution on the production site was evaluated by water and sediment analysis. Furthermore, oysters' nutritional quality was also assessed and related with the consumption of healthy seafood, showing that oysters are a rich source of protein with low fat content and with a high quality index all year around. Results showed that most analysed pollutants were not detected either in oyster tissues or in environmental matrixes (water and sediments). The few pollutants detected in oyster tissues, including both regulated and non-legislated pollutants, such as a few PAHs (fluorene, phenanthrene, anthracene, fluoranthene, pyrene and indenopyrene), FRs (TPPO, TDCPP, DCP, BDE-47, BDE-209 and Dec 602) and PCPs (galaxolide, galaxolidone, homosalate and octocrylene), were present at low levels (in the ng/g dw range) and did not represent a significant health risk to humans. The observed seasonal variations related to human activities (e.g. tourism in summer) highlights the need for environmental protection and sustainable resource exploration for safe seafood production. © 2019 Elsevier B.V.This work was supported by the Structured R&D&I Project INNOVMAR – “Innovation and Sustainability in the Management and Exploitation of Marine Resources” (ref. NORTE-01-0145-FEDER-000035) within the research line “INSEAFOOD - Innovation and valorization of seafood products: meeting local challenges and opportunities”, founded by the Northern Regional Operational Programme (NORTE2020) through the European Regional Development Fund (ERDF). This study was also supported by the SEA-on-a-CHIP project, funded from European Union Seventh Framework Programme (FP7-OCEAN-2013) under grant agreement No. 614168. This work has been also financially supported by the Generalitat de Catalunya (Consolidated Research Group 2017 SGR 01404 – Water and Soil Quality Unit). Biotage is acknowledged for providing SPE cartridges. Authors acknowledge Carlos R. Gomes for helping on multivariated analysis.Peer reviewe