With the objective of the browning controlling enzymatic in fruits, a sequence of experiments of enzymatic inhibition has been developed based on the system enzyme-sustrato-inhibitor (tyrosinase-pyrocatechol-inhibitor).The enzymatic activity of the tyrosinase has been substantially affected by the chelating inhibitors (EDTA), polymeric (chitosane) and enzymatic (papain). The inhibitory effectiveness of the papain has been attributed to its hydrolitic action on the active places 176G and 182E of the tyrosinase. An approach for the constant of Michaelis (Km at 25°C) has given the value of 2,0.

The objective of this study is to propose a method of pre-concentration aqueous samples directly Zn (II) with a commercial cation exchange resin of the type PS-DVB-SO3H strongly acidic Ionac ® C-249. It should be noted that the analysis of Zn atomic absorption flame detector (EAAF) is limited in the sub-ppm levels or ultratrace. For this purpose, we used solutions of Zn (II) to 0.01 ppm (pH = 6.20) were added to which fixed amounts exchanger on a volume of each solution. In exchange, defined residence times, speed of agitation and pH variation with time. Once reached the maximum time, samples were taken for the analysis solution and exchanger EAAF was treated with acid to elute the Zn exchanged and further analysis. The results showed that elution with 6N HCl, gave recoveries between 93 to 96% and pH monitoring function of time possible to monitor the endpoint exchange even with highly ...

With the objective of the browning controlling enzymatic in fruits, a sequence of experiments of enzymatic inhibition has been developed based on the system enzyme-sustrato-inhibitor (tyrosinase-pyrocatechol-inhibitor).The enzymatic activity of the tyrosinase has been substantially affected by the chelating inhibitors (EDTA), polymeric (chitosane) and enzymatic (papain). The inhibitory effectiveness of the papain has been attributed to its hydrolitic action on the active places 176G and 182E of the tyrosinase. An approach for the constant of Michaelis (Km at 25°C) has given the value of 2,0.

The objective of this study is to propose a method of pre-concentration aqueous samples directly Zn (II) with a commercial cation exchange resin of the type PS-DVB-SO3H strongly acidic Ionac ® C-249. It should be noted that the analysis of Zn atomic absorption flame detector (EAAF) is limited in the sub-ppm levels or ultratrace. For this purpose, we used solutions of Zn (II) to 0.01 ppm (pH = 6.20) were added to which fixed amounts exchanger on a volume of each solution. In exchange, defined residence times, speed of agitation and pH variation with time. Once reached the maximum time, samples were taken for the analysis solution and exchanger EAAF was treated with acid to elute the Zn exchanged and further analysis. The results showed that elution with 6N HCl, gave recoveries between 93 to 96% and pH monitoring function of time possible to monitor the endpoint exchange even with highly ...

Residual commercial polystyrene samples (PScr) have been undergone to thermal decomposition processes between 433 hand 673 K (160 at 400 °C). The analyses of the distilled have confirmed that PS has been transformed into styrene with a yield from 45 to 60%. The monomer obtained has been polymerized in suspension using benzoyl peroxide like initiator and divinylbenzene (DVB) in proportions of 2, 6 and 10%. The obtained microspheres of copolymer (PS-DVB) have been sulfonated. After characterization, the results showed that 6% of DVB, presents similar characteristic than the commercial strongly acid cationic exchange resin Sybron Chemicals Inc. Ionac ® C-249.

Muestras de poliestireno comercial residual (PScr) se han sometido a procesos de descomposición térmica entre 433 a 673 K (160 a 400 °C). Los análisis del destilado han confirmado que el PS ha sido transformado a estireno con un rendimiento entre el 45 al 60%. El monómero obtenido se ha polimerizado en suspensión usando peróxido de benzoilo como iniciador y divinilbenceno (DVB) en proporciones de 2, 6 y 10%. Las microesferas obtenidas del copolímero (PS-DVB) han sido sulfonadas. El resultado, después de la caracterización, fue aquel del 6% de DVB presenta características similares a las de la resina comercial de intercambio catiónico fuertemente ácida Sybron Chemicals Inc. Ionac ® C-249.