DETERMINATION OF THE TOTAL INORGANIC AND AMMONIACAL NITROGENS IN WATER BY GAS-PHASE MOLECULAR-ABSORPTION SPECTROMETRY

Based on a vapor-liquid equiribrium of ammonia, a simplified and rapid technique was developed for the determination of the total inorganic and ammoniacal nitrogens in aqueous solution. Ammonium ion was convert ed into gaseous ammonia by adding a sodium hydroxide solution to a sam ple solution. The generated ammonia was directly introduced into a qua rtz cell in order to measure the molecular absorption. As for the dete rmination of the total inorganic nitrogen, the sample solution was pre treated with titanium(III) chloride solution in order to reduce nitrat e and nitrite ions to ammonium ion. The ammonia was then evolved and d etermined in the same manner as mentioned above. The detection limit ( 3 S/N) of 0.01 mu g cm(-3) for both ammonia and the total inorganic ni trogen was obtained. The calibration graph was linear up to 0.8 mu gN cm(-3) for each nitrogen species. The relative standard deviations for five replicate measurements were 3.9, 4.5 and 4.7% for 0.40 mu g cm(- 3) of nitrogen present in the form of ammonium, nitrate and nitrite io ns, respectively. The analytical results for some environmental and in dustrial water samples are presented.