Cellulose acetate membranes lifetime

Enzymes have been attached to a nylon matrix (135-13 7), a pig intestine (138), the hydrophobic membrane of a gas-selective sensor (139), and controlled pore glass (140). Recent comparative studies of the coupling agents GA and benzoquinone support the preferential use of benzoquinone for binding GOD to nylon mesh (13 7), or to cellulose acetate membranes (141) with lysine (13 7). Both investigations report robust electrode behaviors with respect to prolonged exposure to glucose, while lifetimes of the membrane electrodes were ca. 3 months. 

With a similar lactose sensor, Pilloton et al. (1987) assayed lactose in milk samples and obtained a good correlation with the reduction method described by Fehling. The enzyme was fixed to a nylon membrane. A cellulose acetate membrane (molecular cutoff 100 Dalton) was included in order to eliminate electrochemical interferences. The lifetime of the sensor was 1 month. 

The first membranes used, based on cellulose acetate, were uot very resistant to microorganisms, shocks, temperature or pH. Second-generation membranes, made from polysulfone or polyacrylonitrile polymers, were much tougher. Cur-reut third-geueration inorganic membranes have good chemical, physical and heat (temperature >100°C) resistance characteristics. They have almost unlimited lifetimes and are easily cleaned and disinfected. The operating parameters are as follows (a) transmembrane differential pressure,... 

The choice of the polymer support for the liquid membrane matrix is function of not only pore size but also of chemicid compatibili fill. For a ILM with a long lifetime, a matrix material which is inert to the liquid phase is required. The cellulose acetate/nitrate supports used in these experiments, which lost their initial structural... 

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