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- 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.
- 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.
- Sequential injection system exploring the standard addition method for phosphate determination in high salinity samples: interstitial, transitional and coastal watersPublication . Mesquita, Raquel Beatriz Ribeiro; Santos, Inês Carvalho; Bordalo, Adriano Agostinho; Rangel, António Osmaro Santos SilvaA 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.
- Flow injection system using a liquid waveguide capillary cell for the determination of bromated in mineral watersPublication . Santos, Inês C.; Mesquita, Raquel; Páscoa, Ricardo N .M. J.; Tóth, Ildikó V.; Rangel, António O. S. S.
- Corrigendum to "Use of solid phase extraction for the sequential injection determination of alkaline phosphatase activity in dynamic water systems"Publication . Santos, Inês C.; Mesquita, Raquel; Bordalo, Adriano A.; Rangel, António O.S.S.
- Use of Solid Phase Extraction in a Sequential Injection System for the Determination of Alkaline Phosphatase Activity in Plant RootsPublication . Santos, Inês C.; Mesquita, Raquel; Bordalo, Adriano A.; Rangel, António O. S. S.
- Evaluation of some of the main inorganic ions in brine solutions used for sea salt production by flow injection analysis and fourier-mid infrared spectroscopyPublication . Galvis-Sánchez, Andrea C.; Santos, Inês C.; Mesquita, Raquel B. R.; Lopes, João A.; Delgadillo, Ivonne; Rangel, António O. S. S.
- Sistemas de fluxo para a monitorização de nutrientes em águas de transição e costeirasPublication . Mesquita, Raquel; Santos, Inês C.; Bordalo, Adriano A.; Rangel, António O. S. S.
- Paired-ion electrospray ionization – triple quadrupole tandem mass spectrometry for quantification of anionic surfactants in watersPublication . Santos, Inês C.; Guo, Hongyue; Mesquita, Raquel B. R.; Rangel, António O. S. S.; Armstrong, Daniel; Schug, KevinA new paired ion electrospray ionization tandem mass spectrometry method for determination ofanionic surfactants in water samples was developed. In this method, dicationic ion-pairing reagents were complexed with monoanionic analytes to facilitate analyte detection in positive mode electrospray ionization – mass spectrometry. Single ion monitoring and selected reaction monitoring on a triple quadrupole instrument were performed and compared. Four dicationic reagents were tested for the determination of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS),sodium dodecylsul-fate (SDS), dodecylbenzene sulfonic acid (DBS), and stearic acid (SA), among other common anions. The obtained limits of detection were compared with those from previous literature. Solid phase extraction using a C18 cartridge was performed in order to eliminate matrix interferences. A literature review was compiled for the methods published between 2010 and 2015 for determination of anionic surfactants. The otimized method was more sensitive than previously developed methods with LOD values of 2.35, 35.4, 37.0, 1.68, and 0.675 pg for SDS, SA, DBS, PFOS, and PFOA, respectively. The developed method was effectively applied for the determination of anionic surfactants in different water samples such as bottled drinking water, cooking water, tap water, and wastewater.
- Seasonal monitoring of inland bathing waters using a sequential injection method as a fast and effective tool for nutrient quantification (N : P)Publication . Mesquita, Raquel B. R.; Machado, Ana; Santos, Inês C.; Bordalo, Adriano A.; Rangel, António O. S. S.In this work, an expedite flow method for the combined determination of major nutrients, nitrogen base ions (nitrate, nitrite and ammonium) and phosphate, is described for seasonal monitoring of inland bathing waters. Individual determinations were adapted and comprised within the same manifold to attain a comprehensive assessment of the environmental status of natural waters. The multiparametric determination was performed to explore the features of a sequential injection analysis technique yielding a real-time assessment of various parameters and effective in-line sample handling. The sequential injection multiparametric method enabled the determination within the ranges: 15.0-150 mu M nitrate; 0.15-5.00 mu M nitrite; 1.00-60 mu M ammonium; and 0.2-30 mu M phosphate. The determination rates provided a full nutrient analysis within 7 minutes, an overwhelming improvement in relation to the individual determination of each parameter. The described method was successfully applied to seasonal monitoring of six inland bathing waters dealing in-line with sample variability.