Separation of iodate, bromide, nitrite, nitrate, and iodide in seawater by ion chromatography using 1-aminoundecyl group chemically bonded silica columns

The separation and detection of six common inorganic anions (iodate (IO₃⁻), bromate (BrO₃⁻), bromide (Br⁻), nitrite (NO₂⁻), nitrate (NO₃⁻), and iodide (I⁻)) in pure water and 35 ‰ artificial seawater were examined by ion chromatography (IC). As packing materials of separation columns, 1-aminoundecyl group chemically bonded silica (AUS) gels were prepared. Separation of the anions in pure water was achieved using separation columns (150 mm × 4.6 mm i.d.) packed with the AUS gels, 0.1 M NaCl + 5 mM phosphate buffer (pH 4.5) as eluent, and a UV detector (wavelength 225 nm). The anions in artificial seawater were separated and detected with a 300 mm-long column without interferences by matrix anions such as chloride (Cl⁻) and sulfate (SO₄²⁻). The stationary phases have high-capacity anion-exchange/hydrophilic/hydrophobic interaction mixed-modes. The IC system was applied to five inorganic anions, IO₃⁻, Br⁻, NO₂⁻, NO₃⁻, and I⁻ in seawater of the Seto-Inland Sea, Japan. The detection limits (DLs, S/N = 3) were 11 µg L⁻¹ (IO₃⁻), 93 (Br⁻), 1.3 (NO₂⁻), 1.4 (NO₃⁻), and 1.1 (I⁻) for a 100-µL sample injection.