Field evaluation of a novel nitrate sensitive electrode in drainage waters from agricultural grassland

Continuous daily determinations of nitrate were made during a 6 week period with a novel nitrate sensitive electrode deployed in V-notch weirs draining grassland lysimeter plots. The sensor molecule, triallyldecylammonium nitrate was covalently bound to an acrylonitrile–butadiene co-polymer to obtain a robust, rubbery membrane that was incorporated into a commercially obtainable electrode body. A nitrate determination assembly was constructed by interfacing the electrode with a double-junction reference electrode and a temperature probe, through a pre-amplifier to a hand-held digital readout and battery pack. One assembly was positioned in each of two V-notch weirs, receiving drainage water with different nominal ranges of nitrate concentration; set 1, 3–20 ppm and set 2, 0.7–5.1 ppm nitrate-N. Despite conditions conducive to rapid chemical and microbiological degradation, all electrodes remained physically intact, maintained nitrate sensitivity without drift and followed the trends in nitrate concentration well. The electrode performance was compared with laboratory automated chemical determinations made on contemporaneous samples of drainage water.