Gas sensitive field-effect transistors: applications to the monitoring of biotechnological processes Original Research Article

In this paper, new on-line sensors based on pH-sensitive field-effect transitors (pH-FET) are presented for the measurement of ammonia and carbon dioxide during different cultivation processes. Both systems show a linear response between 2.7×10−4 and 2.7×10−2 mol l−1 for ammonia and 2.2×10−4 and 1.5×10−2 mol l−1 for dissolved carbon dioxide. A similar system can be used for the determination of enzyme activities.