Two Schiff-base ligands derived from salicylaldehyde and two 2-pyridylhydrazones were examined for the ultratrace determination of metal ions by reversed-phase high-performance liquid chromatography (HPLC). Although these ligands have been thought to be rather unattractive in inorganic analysis, their renewal in the HPLC methodology was demonstrated in this work. In these ligand systems, certain hard metal ions such as Al(III), Ga(III), V(V), Fe(III), and Co(III) ions, were effectively separated on octadecyl- or cyanopropyl-bonded silica packing materials. A highly sensitive fluorimetric detection of Al(III) ion was achievable with N-salicylidene-2-hydroxyaniline having an O,N,O donor set; although the contamination problem actually limited the detection capability, the calculated detection limit for Al(III) ion was down to 0.1 nM (3 ppt) on a 3 σ blank basis. The chromatography of chelates with 4-N,N-diethylaminosalicylaldehyde-2-pyridylhydrazone seems to be attractive for actual analysis; Al(III), Ga(III), V(V), Fe(III), and Co(III) ions at the sub-ppb to ppb levels have been photometrically detected with a relative standard deviation of less than 5%. The fluorimetric detection using 4-hydroxysalicylaldehyde-2-pyridylhydrazone was very effective to access trace levels of Al and Ga ions, giving detection limits of 3.0 nM and 1.3 nM, respectively (M = mol dm-3).
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