Tsuneji Umeda

Enantiomeric separations of primary amino compounds by nonaqueous capillary zone electrophoresis with a chiral crown ether

Abstract The enantiomeric separation by capillary electrophoresis (CE) in non-aqueous media was examined. The enantiomeric separations of eight primary amino compounds including aromatic amines, amino acids and amino alcohols were achieved by CE in formamide containing a chiral crown ether, (+)-18-crown-6 tetracarboxylic acid. The addition of tetra- n -butylammonium perchlorate as a supporting electrolyte to the electrophoretic solution improved the separation efficiency and gave the baseline enantiomeric separation of dl -1-phenylethylamine which has not been separated by any other separation mode of CE yet.

A sensitive and selective method for the determination of mevalonic acid in dog plasma by gas chromatography/negative ion chemical ionization-mass spectrometry

A sensitive and selective method has been developed for the determination of mevalonic acid (MVA), a cholesterol biosynthetic precursor, in dog plasma using solid-phase extraction in combination with gas chromatography/negative ion chemical ionization-mass spectrometry (GC/NICI-MS). MVA extracted from plasma with a phenylboronic acid-bonded phase cartridge was converted to its pentafluorobenzyl (PFB) ester-cyclic boronate derivative to produce a carboxyltate anion [M-PFB]- in the NlCl mode. PFB ester boronate derivatives of MVA and its internal standard, d3-mevalonolactone, were monitored in the selected ion mode at m/z 213 and 216, respectively. The precision and accuracy of within-run and between-run assays were within 8%. This method was used to follow the diurnal variation of MVA levels in plasma of fasted and fed dogs. The diurnal variations of plasma MVA levels observed between the two groups were similar to those reported previously for human and rat plasma.

Analytical Studies on Isoxazoles. II. A New Fluorimetric Determination of 5-Phenyl-3-isoxazolecarboxylic Acid and Its Application to the Determination of Perisoxal in Plasma

A novel fluorimetric method is described for the determination of 5-phenyl-3-isoxazolecarboxylic acid (PIA) by using 2-hydroxy-1-naphthalenecarbaldehyde (HNA) ; this method was utilized to provide a specific and sensitive assay procedure for perisoxal in plasma. The developed fluorophore was 3-benzoyl-5, 6-benzocoumarin (BBC), obtained by Knoevenagel condensation of benzoylacetonitrile with HNA, followed by cyclization. Linear relationships between fluorescence intensity and concentration existed over the concentration range of 35-350 ng/ml of PIA and 70-700 ng/ml of perisoxal in plasma. This method is 70 times more sensitive than the colorimetric method reported previously.

Analytical Studies on Isoxazoles. I. A New Colorimetric Determination of 5-Substituted 3-Isoxazolecarboxylic Acids and Their Derivatives

A new colorimetric method for the determination of 5-methyl-3-isoxazolecarboxylic acid (MIA) and 5-phenyl-3-isoxazolecarboxylic acid (PIA) was established. This method is based on the decomposition of 5-substituted 3-isoxazolecarboxylic acids to the corresponding β-ketonitriles, followed by condensation with p-dimethylaminobenzaldehyde (DABA). The 5-carboxylic isomers caused no interference in the determination of MIA and PIA. Further applications of this method to perisoxal (II), N-[(dimethylamino) carbonyl]-5-methyl-3-isoxazolecarboxamide (III), and 3-(2-oxazolin-2-yl)-5-methylisoxazole (IV), by decomposition to the corresponding 5-substituted 3-isoxazolecarboxylic acids, followed by the color reaction with DABA, are described.