Buffer capacity worked example

The pH electrode is another suitable transducer for the construction of a urea biosensor. The classical glass electrode is sensitive to H ions and urease is attached in a gel of either polyacrylamide [107] or methacrylamide-aoylamide cqxdymer [108]. me metallic electrodes are also sensitive to H ions (for example, the antimony electrode) and can also be used in conjunction with a urease membrane [109]. The enzyme pH electrode detects a very weak variation in proton concentration arising from an enzymatic reaction, and the signal amplitude is determined by the buffering capacity of the solution. Both the nature of the buffer solution and the working pH value of the biosensor can reduce its practical use. A differential measurement at different pH values can be used to correct for any variation. 

The models were mainly used to size shared resources (e.g., chromatography columns, utilities, and media/buffer preparation tanks) and evaluate various capacity scenarios. The impact of different shift patterns on equipment demand for buffer preparation was also evaluated. Using such tools makes it easier to quantify the trade-off between labor cost and capital investment. The model was able to generate different options based on different work organizations. For example, two options were explored ... 

Figure lb displays examples of pH oscillations observed in Cell II, with glucose level and pH fixed in Cell I. Oscillations persist for about one week, and period increases steadily with time. This drift, along with the ultimate cessation of oscillations, is believed to follow from the slow buildup of gluconate ion in Cell II (see below), which acts as a buffering species (77,72). In the present work, we shall ignore these aspects, which are not relevant to the capacity of the system to initiate oscillations. A more comprehensive analysis of the system is needed to account for these phenomena. 

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