This application is designed to measure low-levels of nitrite in drinking and wastewater samples. Use this method for samples with nitrite concentrations between 0.5 ppm to 0.02 ppm as N. The Orion 9346 Nitrite Electrode measures nitrite in aqueous solution simply, accurately, and economically. Nitrite Interference Suppressor Solution (NISS) is added to all solutions to ensure that samples and standards have similar ionic strength, proper pH, and to reduce the effect of interfering ions. In Table 1, the Orion 920A ISE meter was used to calculate the slope and determine the sample concentration.