The Utilization of Triacontyl-Bonded Silica Coated with Imidazolium Ions for Capillary Ion Chromatographic Determination of Inorganic Anions

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This paper describes the separation and detection of five inorganic anions (I ^- , BrO₃ ^- , NO₂ ^- , Br ^- , and NO₃ ^-) by capillary ion chromatography using 1-alkyl-3-methylimidazolium-coated columns and UV detection at 210 nm. The salts of imidazolium (IM) ions (C2-, C4-, C6-, C8-, C10-, and C18-IMs) are a family of ionic liquids and were newly examined as permanent coating reagents on a triacontyl (C30) -bonded silica reversed phase column. When 40 mM NaCl aqueous solution was used as an eluent, the elution time of these anions was increased with the length of alkyl chain between C2- and C10-IMs, but turned to decrease with C18-IM. Good and faster separations were attained using a C18-IM-coated column with 150 mM NaCl in 25%(v/v) acetonitrile-75%(v/v) water. The method was successfully applied to the determination of nitrite, bromide, and nitrate in seawater and river water.