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Percorrer por autor "Nunes, O. C."

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  • Molinate quantification in environmental water by a glutathione-S-transferase based biosensor
    Publication . Oliveira, Túlio I. S.; Oliveira, Marcela; Viswanathan, Subramanian; Barroso, M. Fátima; Barreiros, Luísa; Nunes, O. C.; Rodrigues, José A.; Lima-Neto, Pedro de; Mazzetto, Selma E.; Morais, Simone; Delerue-Matos, Cristina
    A glutathione-S-transferase (GST)based biosensor was developed to quantify the thiocarbamate herbicide molinate in environmental water.The biosensor construction was based on GST immobilization onto a glassy carbon electrode via aminosilane–glutaraldehyde covalent attachment. The principle supporting the use of this biosensor consists of the GST inhibition process promoted by molinate. Differential pulse voltammetry was used to obtain a calibration curve for molinate concentration, ranging from 0.19 to 7.9 mgL -1 and presenting a detection limit of 0.064 mgL- 1. The developed biosensor is stable,and reusable during 15 days.The GST-based biosensor was successfully applied to quantify molinate in rice paddy field floodwater samples. The results achieved with the developed biosensor were in accordance with those obtained by high performance liquid chromatography. The proposed device is suitable for screening environmental water analysis and, since no sample preparation is required, it can be used in situ and in real-time measurements.
    2013Artigo científico Acesso aberto Ver mais
  • Square-wave voltametric method for determination of molinate concentration in a biological process using a hanging mercury drop electrode
    Publication . Barroso, M. Fátima; Nunes, O. C.; Vaz, M. Carmo V. F.; Delerue-Matos, Cristina
    A square-wave voltammetric (SWV) method using a hanging mercury drop electrode (HMDE) has been developed for determination of the herbicide molinate in a biodegradation process. The method is based on controlled adsorptive accumulation of molinate for 10 s at a potential of -0.8 V versus AgCl/Ag. An anodic peak, due to oxidation of the adsorbed pesticide, was observed in the cyclic voltammogram at ca. -0.320 V versus AgCl/Ag; a very small cathodic peak was also detected. The SWV calibration plot was established to be linear in the range 5.0x10-6 to 9.0x10-6 mol L-1; this corresponded to a detection limit of 3.5x10-8 mol L-1. This electroanalytical method was used to monitor the decrease of molinate concentration in river waters along a biodegradation process using a bacterial mixed culture. The results achieved with this voltammetric method were compared with those obtained by use of a chromatographic method (HPLC–UV) and no significant statistical differences were observed.
    2005Artigo científico Acesso aberto Ver mais