The chromatographic behavior of tris(2-methyl-8-quinolinolato)gallium and other tris(methyl-substituted 8-quinolinolato)galliums was studied with a methanol-water mixture (80 : 20 v/v) containing 5X10-4 mol dm-3 of the corresponding methyl-substituted 8-quinolinol and 2X10 -3 mol dm-3 of a hexamethylenetetramine buffer (pH 6.0). The chromatographic behavior of tris(2-methyl-8-quinolinolato)gallium and tris(2,5-dimethyl-8-quinolinolato)gallium changed when the column was varied. The other tris(methyl-substituted 8-quinolinolato)galliums did not change. Tris(2-methyl-8-quinolinolato)gallium and tris(2,5-dimethyl-8-quinolinolato)gallium were dissociated by EDTA among all of the tris(methyl-substituted 8-quinolinolato)galliums studied. It was suggested that the chromatographic behavior of tris(2-methyl-8-quinolinolato)gallium was influenced by the chelate forming the interaction of the silanol group on the stationary phase.
KeywordsTris(2-methyl-8-quinolinolato)gallium, silanol group, chelate-forming interaction, high-performance liquid chromatographyThe separation and determination of metal chelates with high-performance liquid chromatography (HPLC) is one of the attractive methods for the determination of metal ions.l-4 A precolumn derivatization technique has been popularly used in separation studies of metal chelates with HPLC because of its high reproducibility and sensitivity. Generally, the chelating agents were added to the eluents in order to suppress any dissociation of the chelates for a simultaneous determination with the precolumn derivatization technique. However, every chelate injected into the HPLC column was not separated under the conditions in which the dissociation was suppressed. The chromatographic behavior of the noneluting chelate has not been given much attention.The second effect of the silanol group on the stationary phase influenced the chromatographic behavior of the metal chelates. Although the ion-exchange interaction of the silanol group toward cation chelates has been extensively investigated5'6, studies concerning the chelate-forming interaction of the silanol group have been only qualitative.''8 Suitable metal chelates for studying chelate-forming interactions have not yet been found. This paper describes the silanol effect on the chromatographic behavior of tris(2-methyl-8-quinolinolato)gallium and other tris(methyl-substituted 8-quinolinolato)galliums.
Experimental ApparatusThe HPLC system comprised of a Shimadzu LC-6A pump (Kyoto, Japan), a Japan Spectroscopic 870-UV spectrophotometer (Tokyo, Japan), a Shimadzu RF-535 fluorometric detector, a Rheodyne 7125 loop injector equipped with a 20 µl sample loop, and a Shimadzu R-1231 recorder.Ten commercially available columns were used. A Cosmosil 5C18 column (150 mmX4.6 mm i.d.), a Cosmosil 5TMS column (150 mmX4.6 mm i.d.), and a Cosmosil 5SL column (150 mmX4.6 mm i.d.) were obtained from Nacarai Tesque (Kyoto, Japan). A TSKgeI ODS 80TM column (150 mmX4.6 mm i.d.) and a TSKgeI octadecyl-4PW column (150 mmX4.6 mm i.d.) were obtained fr...
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