Determinación de Zinc en muestras de agua de ríos y red de la provincia de San Luis y aguas envasadas / Zinc determination in river and tap water samples of San Luis province and bottled waters

Resumen Introducción. El Zinc (Zn) es un oligoelemento esencial con gran importancia nutricional e indispensable para el crecimiento normal y la reproducción. Su deficiencia produce anormalidades fisiológicas y estructurales. Así mismo, ingerido en altas concentraciones produce efectos tóxicos, de allí la importancia de su determinación. El agua puede contribuir significativamente a la ingesta diaria de elementos trazas, entre ellos Zn. En el presente estudio se analizó el aporte de Zn en muestras de aguas de ríos y de red (de suministro público) de la provincia de San Luis y en agua mineral natural envasada, por medio de fluorescencia en fase sólida (FFS). Materiales y método.La determinación cuantitativa de Zn en muestras de agua y estándares se basó en la complejación del Zn utilizando una mezcla de o-fenantrolina y eosina a pH 7,5. Luego, una microzona de papel de filtro Blue Ribbon se impregna con la mezcla durante 1 minuto (n=6). Posteriormente, los papeles de filtro se secaron a temperatura ambiente y se colocan en una celda de cuarzo convencional adaptada para FFS. Los resultados obtenidos fueron comparados con la técnica de espectrometría de masas con plasma acoplado inductivamente. Resultados. Las muestras de agua de río analizadas presentaron valores por debajo del límite máximo de Zn recomendado por la Ley Nacional 24051, para la protección de la vida acuática. Las concentraciones de Zn en las muestras de agua de consumo analizadas (de red y envasadas) también estuvieron por debajo de los límites máximos permitidos por el Código Alimentario Argentino y la OMS. Por otro lado, se obtuvo buena concordancia entre las metodologías utilizadas. Conclusiones. El contenido de Zn de las muestras analizadas se encuentra por debajo de los valores máximos permitidos por los distintos organismos de regulación. Las muestras de agua analizadas no contribuyen a satisfacer la ingesta diaria recomendada y presentan valores considerablemente menores a los encontrados en otras regiones. Finalmente, el método aplicado mostró ser una alternativa rápida y sensible para la determinación de Zn en muestras de agua.

Abstract Introduction. Zinc (Zn) is an essential trace element with great nutritional importance and indispensable for normal growth and reproduction. Its deficiency produces physiological and structural abnormalities. Also, if ingested in high concentrations, it produces toxic effects; this is why its determination is very important. Water can contribute significantly to the daily intake of trace elements, including Zn. In this work, Zn concentration was analyzed in river and tap water samples of the province of San Luis and in bottled natural mineral water, by means of solid phase fluorescence (SPF). Materials and method. The quantitative determination of Zn in water samples and standards was based on the complexation of Zn using a mixture of o-phenanthroline and eosin at pH 7.5. Then, a microzone of Blue Ribbon filter paper was impregnated with the mixture for 1 minute (n=6). After this, the filter papers were dried at room temperature and placed in a conventional quartz cell adapted for SPF. The results obtained were compared with the Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) technique. Results. The river water samples analyzed were found below the maximum limit of Zn recommended by National Law 24051 for the protection of aquatic life. The Zn concentrations in the analyzed drinking water samples (tap and bottled water) were also below the maximum limits allowed by the CAA and WHO. Furthermore, a good agreement was obtained between the methodologies used. Conclusions. The Zn content in analyzed samples was below the maximum values allowed by different regulatory organizations. The water samples analyzed do not contribute to satisfying the recommended daily intake and have considerably lower values than those found in other regions. Finally, the method applied proved to be a fast and sensitive alternative for the determination of Zn in water samples.

Determination of progesterone (P4) from bovine serum samples using a microfluidic immunosensor system.

Progesterone (P4) is a steroidal hormone with a vital role in the maintenance of human and animal health. This paper describes the development of an immunosensor coupled to glassy carbon (GC) electrode and integrated to a microfluidic system to quantify P4 from bovine serum samples in a fast and sensitive way. The serum samples spiked with a given P4 concentration and a given P4 concentration bound to horseradish peroxide (HPR) were simultaneously added and, therefore, they competed immunologically with sheep monoclonal anti-P4 antibodies that were immobilized at a rotating disk. HRP in the presence of hydrogen peroxide (H(2)O(2)) catalyzes the chatecol (H(2)Q) oxidation to benzoquinone (Q). Its reverse electrochemical reduction to H(2)Q can be detected at a GC electrode surface at -0.15 V by chronoamperometric measurements. These current responses are proportional to the enzyme activity and inversely proportional to the P4 amount present in bovine serum samples. This P4 immunosensor showed a linear working range from 0.5 to 12.5 ng mL(-1). The detection (DL) and quantification (QL) limits were 0.2 and 0.5 ng mL(-1), respectively. The electrochemical immunosensor had a higher sensitivity than the ELISA method using conventional spectrophotometric detections. However, both methods allowed us to obtain similar detection limits. The immunosensor allowed us to make up to 100 determinations on different samples without any previous pre-treatment. This behavior proved to be suitable to detect P4 in routine veterinary, clinical, biological, physiological, and analytical assays.