BACTERIAL-MEMBRANE ELECTRODE FOR THE DETERMINATION OF NITRATE

A novel potentiometric sensor has been devised for nitrate by coupling the bacterium Azotobacter vinelartdii with an ammonia gas-sensing electrode. Nitrate is reduced to ammonia by a two-step process involving the enzymes nitrate and nitrite reductases contained in the bacterial cells. The response of the bacterial sensor is linear over the concentration range of 1 × 10-5 to 8 × 10-4 M with a slope between 45 to 50 mV/decade. The electrode is useable for a period up to two weeks. Nitrate-containing samples were analyzed with an accuracy and precision between 3 to 4%. The advantages of using intact bacterial cells instead of isolated enzymes to carry out the muitistep reduction are discussed. © 1979, American Chemical Society. All rights reserved.