The simultaneous determination of inorganic nitrogen species (nitrite, nitrate, and ammonium ions) in lake and river-water samples was examined by ion chromatography. Nitrite and nitrate ions were separated on a monolith type of ODS columns equilibrated with DDAB (dilauryldimethylammonium bromide) using 0.5 M sodium chloride + 5 mM phosphate buffer (pH = 5.0) as the eluent and they were detected by UV at 225 nm. Whereas ammonium ion was detected at 710 nm as an indophenol blue derivative after the post-column reaction of ammonium in the presence of dichloroisocyanurate and 1-naphthol. Calibration curves of all ions showed good linearity (more than
R2 = 0.998) in the range of 0∼10 mg/L. The concentration and pH of reagents, the length of reaction coil, and the flow rate of eluent were optimized. The detection limits (
S/N = 3) of nitrite, nitrate, and ammonium ions were 0.2, 0.7, and 2.7 μg/L, respectively. Also, the repeatability (0.1 mg/L,
n = 5) was below 0.15% (retention time), 1.13% (peak area), and 0.88% (peak height). The present method was applied to the simultaneous determination of inorganic nitrogen species in lake and river-water samples. The recovery by analysis of spiked samples was in the rage of 94∼108%.
View full abstract