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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
- Sequential injection system for the spectrophotometric determination of ammonium in Portuguese estuarine watersPublication . Segundo, Ricardo L. A.; Mesquita, Raquel B. R.; Ferreira, M. Teresa S. O. B.; Teixeira, Catarina F. C. P.; Bordalo, Adriano A.; Rangel, António O. S. S.
- 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).
- Determinação de diversos parâmetros em águas por análise por injecção sequencialPublication . Mesquita, Raquel B. R.; Rangel, António O. S. S.
- 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.
- Use of tetramethylbenzidine for the spectrophotometric sequential injection determination of free chlorine in watersPublication . Mesquita, Raquel B. R.; Noronha, M. Lúcia F.O. B.; Pereira, Ana I. L.; Santos, Arménia C. F.; Torres, André F.; Víctor, Cerdà; Rangel, António O. S. S.A sequential injection (SI) method was developed for the spectrophotometric determination of chlorine based on the reaction between tetramethylbenzidine (TMB) and free chlorine. The advantages resulting from the use of TMB are considerable: TMB is highly selective for chlorine, it enables a fairly low quantification limit and represents a less toxic alternative to reagents such as tolidine. The use of this reaction in SI adds other advantages as it enhances the degree of automation, minimisation of reagent consumption (6.8 g TMB/assay) and low effluent production (2.5 mL/determination). The developed method allowed a quantification limit of 90 g/L with a working range of 0.09–1.30 mg OCl−/L and a determination rate of 60 det./h. Based on these features, the system was applied to tap-water and surface water samples with no previous treatment required. The results obtained with the developed system were compared to the reference method, diethyl-p-phenylelediamine (DPD) colorimetric method, and proved not to be statistically different.
- Turbidimetric determination of chloride in different types of water using a single sequential injection analysis systemPublication . Mesquita, Raquel B. R.; Fernandes, Sílvia M. V.; Rangel, António O. S. S.A sequential injection analysis system for the turbidimetric determination of chloride in different types of water is proposed. The determination is based on the reaction of chloride with silver ions and the subsequent measurement of the turbidity caused by silver chloride precipitation. In this method, the use of toxic reagents, such as mercury thiocyanate, commonly employed in most spectrophotometric techniques for chloride determination, is avoided. The main feature of the developed system is the use of a single configuration to carry out the determination over a wide concentration range (2–400 mg L21) by changing only the aspirated sample volume. This characteristic allows the determination of chloride in ground, surface and wastewaters using the same manifold. In addition, a considerable saving of precipitating reagent is achieved due to noncontinuous consumption. The results obtained with the developed system were statistically indistinguishable from those of the potentiometric titration reference method. Relative standard deviations for ten consecutive injections were lower than 3.7%, with a sampling frequency of between 55 and 57 determinations per hour.