Anhydride-derived carboxyl-functionalized silica stationary phase for chromatographic separation of rare earth ions

The key to chromatographic separation of rare earth elements is the column stationary phase. In this work, a new anhydride-derived carboxyl-functionalized silica stationary phase has been successfully prepared through the carboxylation of the aminated silica with 1,2,4-benzenetricarboxylic anhydride (TMA). The carboxyl-functionalized silica (Sil-TMA) is chemically firmly established and does not significantly affect the morphology or structure of the silica gel. Sil-TMA exhibits excellent chromatographic separations of rare earth elements. The feasibility of using Sil-TMA for the chromatographic separation of rare earth elements has been investigated for isocratic and gradient elution, mobile phase concentrations, pH of mobile phase, sample injection volumes and column temperatures. A good separation of rare earth ions (16 REEs except Pm) can be achieved in 55 min using a gradient elution from 40 to 340 mM with α-HIBA. The stability performance of the functionalized column has been verified with a standard deviation between 0.08 and 0.78 % after 10 consecutive repeated injections.