High performance centrifugal partition chromatographic separation of alkaline earth metal ions with bis‐2‐ethylhexylphosphinic acid

The mutual separation of Ca(II), Mg(II), Sr(II), and Ba(II) was studied by high performance centrifugal partition chromatography using 0.16 M bis‐2‐ethylhexylphosphinic acid in heptane as a stationary phase. Two‐step elution of the four metal ions loaded was accomplished with aqueous chloroacetic acid mobile phases (pH 6.50 and 5.30). Ethanol (5%) was added to the pH 6.50 mobile phase for the separation of Sr(II) and Ba(II). The chromatographic conditions were 2,136 partition channels, 800 rpm rotational speed, and 1.5 cm 3 /min flow rate. The elution curve was obtained by monitoring the absorbance of each metal complex post‐labeled with a chromogenetic agent.