Fluorescence determination of closed-shell rare earth metal ions by reversed-phase HPLC with precolumn derivatization using 8-amino-2-[(2-amino-5-methylphenoxy)methyl]-6-methoxyquinoline-N,N,N ',N '-tetraacetate

A sensitive and selective determination of closed-shell rare earth metal io ns (La3+, Lu3+, and Y3+) has been demonstrated using a pre-column chelating reagent {8-amino-2-[(2-amino-5-methylphenoxy) methyl]-6-methoxvquinoline-N ,N,N',N'-tetraacetatic acid (Quin2)}, in reversed-phase HPLC. Although the resolution is still unsatisfactory in this HPLC system, rare- earth metal c helates with this octadentate aromatic polyaminocarboxylate can be detected . This result suggests that these chelates are unexpectedly inert for the d issociation process during elution. The order of elution is quite different from that of the conventional ion-exchange mode separation. Middle-lanthan ide ion-Quin2 chelates were most rapidly eluted, followed by the heavy ones ; the light ones were the most strongly retained. Since ligand-centered flu orescence was observed for only La3+, Lu3+, Y3+, and Gd3+-Quin2 chelates, a nd other fare earth metal ion chelates were sufficiently quenched through a paramagnetic deactivation process, these four metal ions were selectively detected by fluorimetric detection (lambda (ex) = 335 nm, lambda (em) = 500 nm). The detection limits of La3+, Lu3+, and Y3+ were 2.2, 4.0, and 1.9 pp b, respectively, on a 3 sigma basis No interference from each 10-fold exces s of other rare-earth metal ions was observed. The success of this HPLC sys tem for rare-earth ions is derived from the combined properties of the Quin 2 chelates in terms of inertness, chromatographic retention and fluorescenc e detection.