Adsorption FET

It has been suggested that adsorption of dipolar gas molecules at the surface of the insulator of a field-effect transistor can be used as a principle for detection of gases. It would work in only one type of FET discussed in this book. 

Does your answer change if there is a thin layer of gold deposited on the insulator and the gas adsorbs on the outside Au surface  

A glass electrode is connected to the pH meter with copper wire and calibrated with a standard buffer solution. After this calibration, the connecting lead is changed from copper to zinc. Considering the different contact potentials of the Cu and Zn wires, is the calibration still valid or should the electrode be recalibrated  

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