Unique retention properties of metal chelates with 1-(2-pyridylazo)- and 1-(2-thiazolylazo)-2-naphthol-7-sulfonic acids in RP-IP-HPLC

摘要

The reversed-phase ion-pair HPLC behavior of iron(II), cobalt(III), nickel(II) and copper(II) chelates with monosulfonated l-(2-pyridylazo)-2-naphthols (β-PAN-xS) and 1 -(24hiazolylazo)-2-naphthols (β-TAN-xS), in which a sulfonic acid group was involved at the 6- or 7-position of each naphthol ring, were investigated. The effects of the sulfonic acid group position in the naphthol ring, the bulkiness of the tetraalkylammonium counter cation and the characteristics of a nixed solvent as a mobile phase on the retention time of the metal chelates and derivatizing reagent were examined. A remarkable difference in the retention time of each chelate between β-PAN-6S and β-PAN-7S was detected in the system using methanol-water solvent as the mobile phase. Moreover, in only the β-PAN-7S and β-TAN-7S systems, the retention time of the iron(II) and nickel(II) chelates was observed to be shorter than that of the cobalt(III) chelates with the decreasing chain length of the alkyl group of the counter cation. The position of the sulfonic acid group on the naphthol ring has been found to strongly affect the retention time for a metal chelate even at the 6- and 7-positions apart from the coordination site.