Abstract
A simple and rapid on-line separation system for micro amounts of calcium and magnesium in salt was developed. The 8-quinolinol (OX)-loaded active carbon (AC) column selectively separated calcium and magnesium which were presented in salt from sodium chloride as the matrix. The pH of the sample solution was adjusted to 9.5 because calcium and magnesium were retained as OX-complex on the OX-loaded AC column in the pH 9 to 11 region. The OX-loaded AC column could not easily release OX, no matter what type of 2M acids were introduced to the column. The column is so excellent in durability that it can be used at least 1,000 times. The composition of the mobile phase for ion chromatography was 2.5mM of EDTA in 10% methanol. The detection limit was 0.60 ppm for calcium and 1.00 ppm for magnesium in solid salt sample, respectively. The time period required for simultaneous determination of calcium and magnesium was about 20 min. The procedure was successfully applied to the determination of calcium and magnesium ion in several commercially available salts. The proposed preconcentration and separation method for calcium and magnesium based on the OX-loaded AC column is slightly influenced by contamination because it is a closed system and has a good reproducibility.
