New chelating reagents for the complexation of metal ions in aqueous samples, have been developed. The reagents synthesized and tested were 2,6-diacetylpyridine bis(N-methylenepyridiniohydrazone) dichloride (abbreviated H[subscript]2dapmp), 2,6-diacetylpyridine bis(N-methylene-N,N,N-trimethylammonio-hydrazone) dichloride (abbreviated H[subscript]2dapmta), and 2-acetylpyridine-4-ethyl-3-thiosemicarbazone (abbreviated Hapet). All three chelating reagents proved to be useful for the separation and determination of metal ions by reverse-phase high performance liquid chromatography. Both H[subscript]2dapmp and H[subscript]2dapmta formed kinetically stable metal complexes that did not dissociate on the chromatographic column;H[subscript]2dapmp and H[subscript]2dapmta were prepared and characterized. Both complexing reagents contained quaternary ammonium groups which greatly enhanced the water solubility of the reagents and their metal-ion complexes. When the solid H[subscript]2dapmp was dissolved in water, an equilibrium was attained in which three geometric forms co-exist. A rate constant was determined for the equilibrium of the E,E isomer, into the E,Z and Z,Z geometrical isomers. Several metal ions, including Ti(IV), Fe(III), V(V), and U(VI), were determined quantitatively and selectively by complexation with one of the bis hydrazones and chromatographic separation of the metal ion complexes at pH 3.3;At a pH of 7 it was possible to extend the technique and separate and determine 8 metal complexes, in a single run, under gradient conditions on a polystyrene-divinylbenzene polymer based column. Possible separation of rare earth complexes and ion-pairing behavior were also investigated. Linear calibration curve ranges and detection limits are presented for the metal complexes of Sn(II), Ti(IV), Mn(II), Co(II), Cd(II), Sb(III), Cu(II), Ni(II), Pr(III) and U(VI) under neutral conditions. Interferences due to the presence of other metal ions in solution were also investigated at both pH values;Hapet was prepared and extensively characterized. Hapet complexes of In(III), Ga(III), Fe(III), Co(II), Zn(II), Cd(II), Bi(III), and Pd(II) were separated chromatographically using reverse-phase HPLC. Many of these metal ions were also tested for linear calibration ranges, and the effect of foreign ions in the sample solution. The effects of varying chromatographic conditions on metal complex retention are also described.