Sorption of magnesium–picolinate complexes on a macroporous styrene–divinylbenzene copolymer containing immobilized 8-hydroxyquinoline and on the copolymer itself

Abstract

GOCOOL PERSAUD and FREDERICK F. CANTWELL. Can. J. Chem. 70, 926 (1992).The sorbent XAD-OXINE was prepared by covalently binding 8-hydroxyquinoline onto the surface of the macroporous copolymer Amberlite XAD-2 to give about 20% surface coverage. Sorption, onto both XAD-2 and XAD-OXINE, of the magnesium-containing species that are present in solutions of magnesium ion and picolinic acid was studied by the column equilibration/atomic absorption technique at solution pH of 6.00 and 7.50 and ionic strength of 0.25. By using solutions containing various amounts of added magnesium and picolinic acid, in which the ratio of the two metalligand complex species, MgP'IMgP,, varied greatly (P-is the ligand picolinate), it was shown that neither the species Mg2' nor the species MgP+ sorb to an appreciable extent onto the parent polymer XAD-2, but the neutral s ecies MgP, 6' +sorbs strongly and exhibits a linear isotherm. Then, by measuring the sorption isotherm of the species Mg-on XAD-OXINE in the absence of picolinic acid, by measuring the overall sorption of magnesium-containing species on XAD-OXINE in the presence of picolinic acid, and by assuming that the sorption of the species MgPz onto XAD-OXINE was about the same as it was on XAD-2, it was possible to show that the species MgP+ sorbs strongly onto XAD-OXINE, and exhibits linear sorption isotherms. Thus, XAD-OXINE sorbs all three species Mgz+, MgP+, and MgP,.Key words: Amberlite XAD-2, immobilized oxine, magnesium ion. Chem. 70, 926 (1992).On a prepark I'adsorbant XAD-OXINE en liant d'une fagon covalente de la 8-hydroxyquinoleine sur la surface du copolyrnere rnacroporeux Arnberlite XAD-2 de manibre a couvrir environ 20% de la surface. Macroporous copolymers of styrene and divinylbenzene (DVB) find many uses in analytical chemistry. They are routinely used to concentrate trace components from both biological and environmental samples (1, 2). They have been used as packings for moderate efficiency liquid chromatography columns (3, 4) and, in the form of microparticles, as reverse-phase packings for high-efficiency liquid chromatography columns (5-7). These polymers are essentially nonionic and tend to strongly adsorb hydrophobic, nonionic sample molecules from aqueous solution. However, they also sorb ionic sample species (8). They have been used as HPLC packings for "dynamic ion exchange" chromatography of lanthanide ions (9). In this latter type of application a large surfactant ion is reversibly sorbed onto the surface of all of the packing in the column and lanthanide sample ions are chromatographed on this reversibly modified packing.Macroporous styrene-DVB copolymers have also been derivatized by covalently attaching various groups to the polymer surface. Low-capacity cation and anion exchangers have been prepared by attaching sulfonate or quaternary 'Author to whom correspondence may be addressed. ammonium groups. They have been used as liquid chromatographic column packings for separating both organic and inorganic ions (10,11). A physico-chemical model has be...