Analytical Sciences

Abstract − Analytical Sciences, 32(10), 1123 (2016).

Determination of Inorganic Anions in Seawater Samples by Ion Chromatography with Ultraviolet Detection Using Monolithic Octadecylsilyl Columns Coated with Dodecylammonium Cation
Yuuta HORIOKA,* Ryuki KUSUMOTO,** Kengo YAMANE,* Ryosuke NOMURA,* Takeshi HIROKAWA,*** and Kazuaki ITO*,**
*Cluster of Biotechnology and Chemistry Systems, Graduate School of Systems Engineering, Kindai University, 1 Umenobe, Takaya, Higashi-Hiroshima 739-2116, Japan
**Department of Biotechnology and Chemistry, Faulty of Engineering, Kindai University, 1 Umenobe, Takaya, Higashi-Hiroshima 739-2116, Japan
***Emeritus Professor, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan
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.