Selectively Enhanced Retention of Neutral Iron(II) Complex in RP-LC with o-Hydroxy Pyrimidylazo Compounds as Precolumn Derivatizing Reagent

Abstract

The diazo component of o-hydroxy heterocyclic azo compounds showed a remarkable effect on the retention of their neutral complexes of iron and nickel as a precolumn derivatizing reagent in the separation of metal ions by RP-HPLC using an octadecyl-bonded silica gel column. High resolutions of iron and nickel complexes were obtained with pyrimidyl derivatives. Acetonitrile-water or acetone-water was more suitable as a mobile phase than alcohol-water with regard to the separation of these metal ions. Thermodynamic study showed that the difference in transfer enthalpies of iron and nickel complexes from the mobile phase to the stationary phase dominated the resolution of two complexes with pyrimidyl compounds. High resolutions obtained by use of pyrimidyl compounds were ascribed to selectively enhanced retention of the iron complexes from the comparison with the retentions of the zinc complexes.