Hiromasa Katoh

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.

Optical resolution of 2-hydroxy acids by high-performance ligand exchange chromatography

SummaryUsing an MCl GEL CRS10W column, which was packed with octadecyl silica (ODS) coated with N,N-dioctyl-L-alanine, optical resolution of 2-hydroxy acids was performed. The optical resolution of mandelic acid derivatives and C2 to C5 2-hydroxy acids was carried without any pretreatment. The MCl GEL CRS10W column could resolve amino acids and 2-hydroxy acids. For their selective detection, a post-column method was employed in which the specific color reaction of 2-hydroxy acids with iron(III) ion was utilized. For the analysis of foodstuffs, in which amino acids and 2-hydroxy acids often coexist, the present method was found to be effective in distinguishing between these enantiomers.

Karl Fischer coulometric titration using a diaphragmless cell.

The authors investigated Karl Fischer coulometric titration using a diaphragmless cell. Many samples, such as hydrocarbons, alcohols and polymers, were analyzed by the present method and the conventional method using a cell with a diaphragm. The relationship between both methods showed good agreement (relation coefficient, r =0.99996). Compounds containing a nitro group showed higher analytical values, because the products electrolyzed at the cathode reacted with the iodine produced at the anode. Present method is suitable for the coulometric titration/the moisture vaporization method in which the moisture in samples is introduced into the electrolyzing cell by heating and purging.

Determination of moisture in polymers by heating vaporization-Karl Fischer coulometric titration method.

ポリマー中の水分の定量について,溶解-カールフィッシャー(KF)容量滴定法と加熱気化-KF電量滴定法との比較を行った.前者に比べ,後者は分析操作が非常に簡単で,分析時間も10～30分と短く,定量下限も約10ppmと低い.又,再現性も5%以内と良好なため,加熱気化-KF電量滴定法は十分公定法として使用することが可能である.