Abstract
Trace levels of nitrite in river water were successfully determined with a method involving a two-step reaction to form an azo dye, followed by hexanol extraction and spectrophotometric measurement at 610 nm. The two-step reaction consists of: (1) reaction of the nitrite with 4-nitroaniline in the presence of 0.1 M HCl to form 4-nitrophenyldiazonium chloride, and (2) reaction of the diazonium ion with naphth-l-ol to form a purple azo dye. This dye is extracted with hexanol, which is more suitable than butanol, pentanol, isopentanol, or octanol. Absorbance is constant from 15 to 40 C and does not change more than + or - 2% up to 30 hours. The practical range for determination of nitrite by this method is 0.035-0.123 ppm. The 12 river water samples, all diluted from 4 ml to 50 ml prior to analysis, contained 0.36 to 0.83 ppm nitrite, which agreed well with results from the conventional sulfonamide-N-(l-naphthyl)-ethylenediamine dihydrochloride method. Ethylenediaminetetraacetic acid or tartrate masking agents prevented interference from a variety of ions, including Fe, Bi, and Cu. A complete table of tolerances is presented. (Cassar-FRC)