311-75 Nitrate Mono ION Selective ElectrodeION selective electrode for testing food, water, plants etc About Nitrate Mono ION Selective Electrode. This electrode requires a separate reference electrode. For applications where greater accuracy is required (especially when ION levels are low). Applications Drinking water Sewage effluent Plants Fertiliser Meat Baby Food Potatoes Specifications Concentration Range: 1M 5 x 10 8M Lower Limits (ppm): 0. 08 Ref. Electrode: R2 Temp Range : 0 50 Main