A new N-hydroxyethyliminodiacetic acid modified core-shell silica phase for chelation ion chromatography of alkaline earth, transition and rare earth elements

Bare core-shell silica (1.7 um) has been modified with iminodiacetic acid functional groups via standardsilane chemistry, forming a new N-hydroxyethyliminodiacetic acid (HEIDA) functionalised core-shellstationary phase. The column was applied in high-performance chelation ion chromatography and eval-uated for the retention of alkaline earth, transition and heavy metal cations. The influence of nitric acideluent concentration, addition of complexing agent dipicolinic acid, eluent pH and column temperatureon the column performance was investigated. The efficiencies obtained for transition and heavy metalcations (and resultant separations) were comparable or better than those previously obtained for alter-native fully porous silica based chelation stationary phases, and a similarly modified monolithic silicacolumn, ranging from ~15 to 56 um HETP. Increasing the ionic strength of the eluent with the additionof KNO₃(0.75 M) and increasing the column temperature (70 Celsius degree) facilitated the isocratic separation of amixture of 14 lanthanides and yttrium in under 12 min, with HETP averaging 18um (7um for Ce(III))