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Automated solid-phase spectrophotometric system for optosensing of bromate in drinking waters

Publication . Oliveira, Sara M.; Oliveira, Hugo M.; Segundo, Marcela A.; Rangel, António O. S. S.; Lima, José L. F. C.; Cerdà, Vıctor

An automated method based on an optosensor included in a multisyringe flow injection system was developed for the determination of bromate in waters for human consumption. The optosensor was based on the formation of a colored radical cation after oxidation of chlorpromazine by bromate and its selective uptake in a mixed-mode cation exchanger sorbent (Discovery DSC-MCAX), placed on a flow-through spectrophotometric cell. In-line regeneration was attained by methanol + 5% (v/v) ammonia, fostering the application of the same sorbent portion up to 180 determinations. Parameters affecting the reaction development and uptake of the colored compound were studied and optimized, while in-line addition of sulfite ($0.100 g L 1) prevented interference from hypochlorite. The proposed methodology allowed the determination of bromate up to 50.0 mg L 1, with 0.9 mg L 1 as the limit of detection, meeting the requirements of current EU and USA legislation. Application to real drinking water samples was successful, with a mean recovery of 100.2 2.8% for spiked levels of 5.0, 10.0 and 25.0 mg L 1. Repeatability was good (RSD < 3.6%, n ¼ 10) with a determination throughput of 8 h 1, fostering the application to on-line control of water disinfection processes.

2012Journal article

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Simultaneous determination of tartaric acid and potassium in wines using a multicommuted flow system with dialysis

Publication . Oliveira, Sara M.; Lopes, Teresa I.M.S.; Tóth, Ildikó V.; Rangel, António O.S S.

A multicommuted flow system with the propulsion device placed before detection is proposed for the determination of tartaric acid and free potassium in table and Port wines. A dialysis unit was introduced to increase sample dilution and minimize matrix interferences. The determination of tartaric acid was based on the spectrophotometric monitorization of the complex formed by the dialyzed analyte with vanadate. Potentiometric measurement of potassium was carried out through an ion selective tubular electrode. Dynamic linear ranges of 0.500–5.00 g L−1 and 390–2000mgL−1 were achieved for tartaric acid and potassium determinations, respectively. Detection and quantification limits of 0.1 and 0.4 g L−1 of tartaric acid were obtained, respectively. For the potentiometric determination, a detection limit of 1×10−4 mol L−1 was achieved. The accuracy of the method was assessed by analysis of 30 wine samples by the proposed methodology and manual procedures. There were no statistical differences between the 2 sets of results, in both determinations. Relative standard deviations lower than 2.1 and 2.4% were attained by the spectrophotometric and potentiometric measurements, respectively. A determination rate of 52 h−1 was achieved.

2010Journal article

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