Toyohide Takeuchi

Direct coupling of micro high-performance liquid chromatography with fast atom bombardment mass spectrometry

Abstract An interface for direct coupling of micro high-performance liquid chromatography with fast atom bombardment mass spectrometry has been developed. The interface was made of fused-silica capillary tubing, the end of which was attached to a stainles-steel frit. The mobile phase contained glycerol, which functioned as the matrix, and the solvent was immediately vaporized on the surface of the frit. The argon beam stroke the surface of the frit and its position was adjusted so that the solute could be effectively ionized. The performance of the interface was examined using bile acids as the test solutes.

High-performance micro packed flexible columns in liquid chromatography

Abstract Columns of flexible fused-silica tubing packed with commercially available materials have been prepared. The performance of these columns was examined with acetonitrile-water as the mobile phase and polynuclear aromatic hydrocarbons as the solutes. A 10 cm × 0.25 mm I.D. column yielded about 7000 plates (plate height 14 μm), a performance comparable to that of conventional high-performance liquid chromatography. The effects of column length and injection volume on the column efficiency are discussed.

Micro-high-performance liquid chromatography with long micro-packed flexible fused-silica columns

Abstract Coupling of several 20 cm × 0.25–0.35 mm I.D. micro packed flexible fused silica columns in series is a simple technique for attaining high efficiencies in micro high-performance liquid chromatography. Reversed-phase and gel permeation chromatography using 40–140-cm columns are demonstrated. A 140-cm column packed with G 1000H (5 μm) attained ca. 100,000 plates in gel permeation chromatography. These columns were employed to resolve complex polychlorinated biphenyl mixtures or the constituents of water.

Direct coupling of micro high-performance liquid chromatography with fast atom bombardment mass spectrometry. II. Application to gradient elution of bile acids.

A new system without a moving belt has been developed for direct coupling of micro high-performance liquid chromatography with fast atom (xenon or argon) bombardment mass spectrometry. The structure of the interface was basically the same as used previously, but the mass spectrometer was modified by adding both a liquid nitrogen trap between the ion source housing and the diffusion pump, and a position adjuster for the interface. Stable ionization of the solute in a glycerol matrix is achieved at flow-rates below 2 microliter/min. The system was applied to the analysis of bile acids by gradient elution chromatography. Steady baselines were observed in the mass chromatograms.

Speciation of mercury compounds in waste water by microcolumn liquid chromatography using a preconcentration column with cold-vapour atomic absorption spectrometric detection

Abstract A microcolumn liquid chromatographic method with cold-vapour atomic absorption spectrometric detection was developed for the speciation of mercury compounds in waste water. The sample solution containing mercury at the 4-ng level was injected onto a preconcentration column (27 mn × 0.51 mm i.d.) packed with Develosil-ODS (30 μm) and eluted with cysteine-acetic acid through a separation column (125 mm × 0.5 mm i.d.) packed with STR-ODS-H (5 μm). After oxidation, tin(II) chloride in sodium hydroxide solution was used to reduce mercury compounds to mercury. The generated mercury vapour was swept from a gas-liquid separator by argon into the detector cell and monitored at 253.7 nm. Mercury(II) chloride, methylmercury chloride and ethylmercury chloride, were well resolved and the determination was completed in less than 16 min. The method was successfully applied to the speciation of mercury compounds in waste water.

Continuous gradient elution in micro high-performance liquid chromatography

Abstract A continuous gradient elution method for micro high-performance liquid chromatography was developed. Gradient eluent was supplied from a mixing vessel into which another solution was continuously fed by a micro syringe-type pump. The gradient profiles observed agreed with calculated plots. Some typical continuous gradient separations are described.

Enantiomeric resolution of dansyl amino acids by micro high-performance liquid chromatography with β-cyclodextrin inclusion complexes

Abstract Enantiomeric resolution of dansyl amino acids by micro high-performance liquid chromatography with β-cyclodextrin inclusion complexes was investigated. Chromatographic parameters which affect enantiomeric resolution were examined. Twelve pairs of dansyl amino acids were separated in a single chromatographic run.

Application of ultra-micro high-performance liquid chromatography to trace analysis

Abstract A pre-column concentration technique in ultra-micro high-performance liquid chromatography has been developed and applied to trace analysis. The micro pre-columns are composed of PTFE tubing (3–12 × 0.1–0.2 mm I.D.) packed with commercially available materials. Components in water or samples are collected in a micro pre-column and then separated on ultra-micro packed columns ( ca. 10 cm × 0.12 mm I.D.). Polynuclear aromatic hydrocarbons, phthalates and corticosteroids can be separated on these columns, in spite of the small dimensions. Phthalates in water and corticosteroids in serum have been determined by this technique.

Studies of open-tubular microcapillary liquid chromatography : III. β,β′-oxydipropionitrile and ethylene glycol stationary phases

Abstract Capillary columns coated with β,β′-oxydipropionitrile and ethylene glycols have been applied successfully in open-tubular microcapillary column liquid chromatography. These stationary phases were spread out well on a soda-lime glass surface treated with alkaline solution. The capillary columns obtained have efficiencies of about 1500 theoretical plates per metre. Xylenol isomers, aromatic amines and phthalates were separated in a normal-phase system.

High-performance liquid chromatography using flexible fused-silica micro-packed columns

Abstract High-resolution flexible fused-silica micro packed columns were prepared by coupling 50-cm columns in series. These columns produced large numbers of theoretical plates (more than 100,000) and were successfully applied to the separations of epoxy oligomers and polychlorobiphenyl mixtures in gel permeation chromatography and reversed-phase liquid chromatography, respectively.