Nitrate and ammonium ion-selective electrodes as sensors. I. In bacterial growth curves for isolation of nitrate and nitrite reductases from Escherichia coli

Ammonium and nitrate ion-selective electrodes were applied as sensors in bacterial growth curves for the isolation of nitrate and nitrite reductase. A nitrate ion-selective electrode was used as a successful new technique for the assay of nitrate reductase activity: the decrease in nitrate concentration was followed continuously. Likewise, an ammonium ion-selective electrode was used to follow the increase in ammonium ion concentration. Excellent agreement with spectrophotometric procedures ( < 5%) was obtained.