Improvement of Photometric Determination of Trace Amounts of Nitrate and Nitrite in Water

Abstract

An improved rapid method of extraction-photometric determination of trace amounts of nitrate and nitrite in water was developed. Nitrate was quickly reduced to nitrite at pH 3.0 in 5 min with freshly prepared Cd sponge, which was produced in situ by action of Zn powder in dilute solution of CdCl2 in presence of ammonium chloride. At pH 2.0, HNO2 diazotized with p-aminoacetophenone, which was then coupled with N-(1-naphthyl)-ethylenediamine. The azodye formed was extracted into n-butanol at pH 2.0 in the presence of .beta.-naphthyl sulfonic acid and aluminum nitrate. The absorbance was measured at 550 nm. The molar absorptivity of the extract was .apprx. 4.8 .times. 104 l .cntdot. mol-1 .cntdot. cm-1. The ions normally present in water did not interfere when sodium metaphosphate was added as a masking agent. Water from several sources was analyzed and results were satisfactory.