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.

Determination of Inorganic Anions in Seawater Samples by Ion Chromatography with Ultraviolet Detection Using Monolithic Octadecylsilyl Columns Coated with Dodecylammonium Cation.

A fast and sensitive ion chromatographic method for the simultaneous determinations of six inorganic anions [iodate (IO3-), bromate (BrO3-), bromide (Br-), nitrite (NO2-), nitrate (NO3-), and iodide (I-)] in seawater is described using dodecylammonium (DA+)-coated monolithic octadecylsilyl (ODS) columns, a concentrated aqueous NaCl mobile phase containing dodecylammonium chloride (DAC), and a UV detector. The DA+-coated monolithic ODS columns show greater retention for iodate and weaker retention for iodide, compared to dilauryldimethylammonium (DDA+)-coated monolithic ODS columns. Six anions were determined within 12 min with baseline separation without interferences by matrix ions, such as Cl- and SO42-, in seawater, compared to a DA+-coated particulate ODS column (it took 25 min per sample) obtained previously. The detection limits (DLs) were comparable to the DA+-coated particulate ODS column: IO3- (7.7 µg L-1), BrO3- (20), Br- (88), NO2- (0.9), NO3- (1.9), and I- (0.9) with a 100-µL sample injection. A larger sample volume injection lowered the DLs of IO3-, BrO3-, and I-. The good performance was maintained for ca. 2 years examined. The robust IC system developed in the present work was successfully applied to real seawater samples without sample dilution in the recovery rates of 93 - 104% for all ions.