Simultaneous automated determination of chloride, nitrite, nitrate, and ammonia in water and wastewater

Abstract

An automated system capable of simultaneous determination of chloride, nitrite, nitrate, and ammonia in about 2 ml of fresh water or wastewater is described. The four compounds are determined using modifications of established colorimetric procedures. Results can be reported at a true rate of five samples per hour with a relative standard deviation at optimum concentrations of less than 2%. Detection limits are 1 ppm Cl for chloride and 1, 5, and 5 ppb N for nitrite, nitrate, and ammonia, respectively. Sample pH adjustment is not required from 0.0002 N H2SO4 (pH 3.7) to 0.005 N NaOH (pH 11.2). Fresh water and wastewater samples were analyzed for nitrite and ammonia by the proposed procedure and by the manual sulfanilic-naphthylamine and nesslerization method. Analysis by the student t-test showed no significant difference between the paired sets of data (P > 0.5). When potable and wastewater samples were spiked with sodium chloride, potassium nitrate, sodium nitrite, and ammonium chloride and analyzed, average recoveries were 99 to 103%.