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- Assessment of the impact synthetic Fe(III)-chelates amendment in soil microbial community dynamicsPublication . Machado, Ana; Mesquita, Letícia S.; Rangel, Maria; Mesquita, Raquel B. R.; Rangel, António O. S. S.; Bordalo, Adriano A.
- Raoultella ornithinolytica: an opportunistic pathogen in the oral cavity of chronic kidney disease patientsPublication . Costa, Carolina F. F. A.; Campos, Carla; Merino, Ana; Silva, Nádia; Mesquita, Raquel B. R.; Rangel, António O. S. S.; Sampaio-Maia, Benedita
- 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.
- Development of a sequential injection gas diffusion system for the determination of ammonium in transitional and coastal watersPublication . Segundo, Ricardo Alves; Mesquita, Raquel B. R.; Ferreira, Maria Teresa Soares Oliveira Barbosa; Teixeira, Catarina Fernanda Carvalho Pinheiro; Bordalo, Adriano Agostinho; Rangel, António O. S. S.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).
- Development of a low pressure chromatographic flow system for monitoring the biodegradation of ofloxacin and ciprofloxacinPublication . Santos, Inês C.; Mesquita, Raquel B. R.; Amorim, Catarina L.; Castro, Paula M. L.; Rangel, António O. S. S.In this work, we propose a simple low pressure chromatography method with a high throughput for monitoring the biodegradation of fluoroquinolones. Fluoroquinolones are a class of antibiotics that have been accumulating in the environment as a consequence of their release from different sources, namely hospital waste. It has been found that wastewater treatment plants are not able to completely remove this type of micro-pollutants and so, alternative solutions are necessary. Some biodegradation studies have been done but the HPLC-based methodologies used to monitor the degradation process usually require high cost instrumentation such as analytical columns and detectors. For this reason, a 1 cm monolithic column was coupled to a flow injection system and used for the simultaneous quantification of ofloxacin and ciprofloxacin with UV detection at 295 and 275 nm, respectively. LODs of 0.5 and 0.29 mg L-1 for ofloxacin and ciprofloxacin were obtained, respectively, with repeatability within the range of 2–10%. The developed method was successfully applied to monitor the biodegradation of ofloxacin and ciprofloxacin by the strain Labrys portucalensis F11. The results proved that the low pressure chromatography method is a simpler, cheaper, and faster alternative to monitor biodegradation studies.
- Sequential injection application of an expressly designed 3-hydroxy-4-pyridinone funcionalized with a polyethylene glycol chain for the spectrophotometric determination of ironPublication . Rangel, António O. S. S.; Miranda, J. L. A.; Mesquita, Raquel; Rangel, M.
- Development of a flow method for the determination of phosphate in estuarine and freshwaters - Comparison of flow cells in spectrophotometric sequential injection analysisPublication . Mesquita, Raquel B. R.; Ferreira, M. Teresa S. O. B.; Tóth, Ildikó V.; Bordalo, Adriano A.; McKelvied, Ian D.; Rangel, António O. S. S.A sequential injection system with dual analytical line was developed and applied in the comparison of two different detection systems viz; a conventional spectrophotometer with a commercial flow cell, and a multi-reflective flow cell coupled with a photometric detector under the same experimental conditions. The study was based on the spectrophotometric determination of phosphate using the molybdenum-blue chemistry. The two alternative flow cells were compared in terms of their response to variation of sample salinity, susceptibility to interferences and to refractive index changes. The developed method was applied to the determination of phosphate in natural waters (estuarine, river, well and ground waters). The achieved detection limit (0.007 mu M PO43-) is consistent with the requirement of the target water samples, and a wide quantification range (0.024-9.5 mu M) was achieved using both detection systems.
- Development of a Turbidimetric Sequential Injection System to Monitor the Codfish Desalting ProcessPublication . Santos, Inês C.; Mesquita, Raquel B. R.; Galvis-Sánchez, Andrea C.; Delgadillo, Ivonne; Rangel, António Osmaro S. S.Salt-cured codfish represents an ancient process of preservation but requires the rehydration of the codfish with the correspondent salt removal. This work describes the development of a sequential injection system for the online turbidimetric determination of chloride during a simulated desalting process. The samples are directly aspirated to the manifold with no need for previous offline treatments; this was possible due to the use on an inline dialysis process; a quantification range from 50.0 mg/L to 20.0 g/L was established using the same manifold configuration. For monitoring the entire process, involving several chloride determinations (ca. 10), less than 3 mL of the desalting water was needed. Furthermore, the overall reagent consumption was quite low: 0.211 mg of AgNO3, 30.6 mg of HNO3, and 31.1 μg of PVA per determination. The accuracy of the system was evaluated by comparison with a potentiometric reference method. The determination rate was 28 and 31 h−1 according to the chloride concentration range. Several simulated desalting processes, under different conditions, were effectively monitored with the developed method.
- Exploring 3-hydroxy-4-pyridinone chelators synthetic versatility to attain tailor made low toxicity chromogenic reagents for iron speciation in water samplesPublication . Rangel, António O. S. S.; Mesquita, Raquel; Rangel, M.
- Developing integrated flow analysis tools to monitor the soil-water interface: Application to laboratory scale soil columns (LSSC)Publication . Mesquita, Raquel B. R.; Costa, Carolina F. F. A.; Mesquita, Letícia S.; Rangel, António O. S. S.