ISFET (Ion-Sensitive Field-Effect Transistor) pH electrodes have been available for quite some time. Nelson-Jameson customers engaged in Food Processing need to be aware that a bias associated with ISFET and food samples is commonly observed. In many cases, they do not generate the same results as traditional electrodes that incorporate glass for pH sensing.
At Nelson-Jameson, we have found that ISFET electrodes appear to compare quite well with traditional electrodes when used in virtually clear liquids; the bias becomes much greater in opaque and other solutions with greater amounts of solids. Customers that insist on ISFET style electrodes should take into consideration the potential for bias in their pH analysis for food processing applications.
Several manufacturers offer ISFET electrodes that may perform well in specific applications, and these are available through Nelson-Jameson.