Hideaki Kiniwa

Optical resolution of amino acids, peptides and hydroxycarboxylic acids using a new chiral column for ligand-exchange chromatography

Abstract The enantiometric resolution of amino acids, amino acid derivatives, peptides and hydroxycarboxylic acids was investigated using a chiral column of the ligand- exchange type. It was found that this column separated all of these compounds satisfactorily. Columns containing either a d - or l -ligand gave almost identical chromatograms, except that the retention order for a pair of chiral isomers was reversed. These columns could be applied to resolve simultaneously ten different types of dL - amino acids. Optically active impurities present in d and l -amino acids could be determined at concentrations down to about 100 ppm.

General evaluation and application to trace analysis of a chiral column for ligand-exchange chromatography

Abstract The direct optical resolution of more than twenty amino acids, including the separation of four isomers of allo- dl - and dl -isoleucine, can be achieved on a novel ligand-exchange column, MCI GEL CRS10W. The stationary phase, N,N-dioctyl- l -alanine-coated octadecylsilica, shows a stronger affinity for hydrophobic amino acids than for hydrophilic amino acids. General evaluation of the column clarified the effects of the column temperature and CuII concentration in the eluent on the chiral separation. The determination of trace enantiomers in some commercially available d - and l -amino acids was performed, revealing the presence of 0.03–0.5% of the trace enantiomer. The efficient resolution of strongly retained hydrophobic amino acids and hydroxycarboxylic acids was also achieved on a shortened column.

Transport of organic and inorganic solutes through charged mosaic composite membranes

Abstract A template pattern with alternating poly(4-vinylpyridine) (P4VP)/poly(vinyl alcohol) (PVA) lamellae was fabricated upon a microporous poly(vinyl chloride) (PVC) membrane by casting of poly[4-vinylpyridine(4VP)-g-vinyl alcohol (VA)] graft copolymer. After a treatment of both binding of microporous membrane with graft copolymer and domain fixing of the PVA matrix, a dilute solution of poly[acrylic acid (AA)-benzyl N,N -dimethyldithiocarbamate (DMTC)]/P4VP or poly[sodium p -styrenesulfonate (SSS)-DMTC]/P4VP binary blend was cast on this template surface. Two types of weak acid/strong base or strong acid/strong base microdomains formed by phase growth were oriented perpendicularly to the membrane surface. After the chemical treatments: introduction of the charge and domain fixing of ion exchange regions, two types of such mosaic microdomains could be constructed on a microporous membrane. We studied the transport behaviors of organic and inorganic solutes through charged mosaic composite membranes. The permeability of inorganic electrolyte, such as KCl was about 20-fold compared to those of organic nonelectrolytes, such as glucose and sucrose. l -Phenylalanine exhibits a low value of permeability at the pH of its isoelectric point.