Genkichi Nakagawa

Open-tubular microcapillary liquid chromatography with electro-osmosis flow using a UV detector

Abstract The linear velocity of electro-osmosis in a capillary tube 30–90 cm x 30–200 μm I.D. was measured. The physical and geometrical parameters of electro-osmosis and its use are discussed. The H value for an unretained solute in disodium hydrogen orthophosphate—water is about one thirtieth of that obtained under laminar flow conditions. Chromatographic separations of aromatics using an octadecylsilane capillary column of I.D. 30 μm are demonstrated.

Separation of organic and metal ions by high-voltage capillary electrophoresis

Abstract Electro-osmotic flows were measured in Pyrex glass capillary, fused-silica capillary and poly(fluoroethyl—propylene) tubings. The electro-osmotic flow exhibited a good linear relationship with electric current density. The factors which influence electro-osmosis and separations are discussed. Good separations of pyridinium salts, sulphonic acids and metal ions were demonstrated, eluting towards the negative or positive terminal at up to 16 kV in aqueous solution. Theoretical plate numbers for pyridinium salts were around 1.5 · 105–2 · 105.

Sample dispersion with chemical reaction in a flow-injection system

Abstract Computer simulations of signals based on a dispersion equation involving diffusion, convection and chemical reaction terms are reported for systems with and without chemica reaction. 2-(2-Thiazolylazo)-4-methyl-5-(sulfomethylamino)benzoic acid (TAMSMB) is used as the reagent because it reacts very quickly with copper(II) and much more slowly with nickel(II). Comparison of experimental signal profiles with the simulated ones enables sample dispersion from the reaction rates to be elucidated. Concetration profiles of the reaction product in a straight, narrow tube were also stimulated; they explain satisfactorily the signal profiles obtained experimentally.

Open-tubular microcapillary liquid chromatography with 30–40 μm I.D. columns

Abstract The effect of external column volume on apparent column efficiency is disscussed using the peak width expressed in volume units. Although the effect is very large for non-retained solutes, it decreases sharply for retained solutes. Columns with a high k′ value and a high theoretical plate number (e.g., 160,000), were demonstrated. Split sample introduction and the method of calculating the thickness of the stationary phase layer are also discussed.

Determination of twelve elements in botanical samples with inductively coupled plasma atomic emission spectrometry after leaching with tetramethylammonium hydroxide and ethylenediaminetetraacetic acid

Abstract The combined use of tetramethylammonium hydroxide (TMAH) and ethylenediaminetetraacetic acid (EDTA) was effective for leaching inorganic constituents from botanical samples for their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). A powdered sample of 50 mg and 1 ml each of 25% TMAH and 200 mM EDTA were heated for 4 h in a drying oven of 120°C using a doubly sealed PTFE vessel with a metal jacket. To the suspended solution in a small vessel 2 ml of water were added, the pH was adjusted to 8 and the suspension was centrifuged. The supernatant was used for sequential measurements of major and minor constituents by ICP-AES. The results obtained for some standard reference samples of botanical origin agreed well with the certified or reported values, except for slightly low recoveries of aluminium and iron.

Open-tubular liquid chromatography with 5–10-μm I.D. Columns☆

Abstract The use of micro-bore capillary columns of I.D. 5–10 μm in liquid chromatography is discussed. Separations using 6–11-μm I.D. columns are described, and their h-v relationships are discussed in relation to theoretical values. An apparatus for in-column injection is described.

General considerations in compleximetric titrations

Abstract Some general theoretical expressions are proposed for various titration curves involved in compleximetric titrations. The effects of some critical factors, such as pH, auxiliary complexing agents and presence of a second metal, are all taken into account in these expressions. The sharpness and errors of potentiometric, amperometric and photometric (visual) indication of end-points are also theoretically discussed.

Preparation and examination of calcium ion-selective electrodes for flow analysis

Abstract The preparation of calcium ion-selective electrodes based on known alkylphenylphosphate exchangers or on the ETH 1001 ionophore, and their use in a flow-through cell in a flow-injection system for the determination of calcium are described. The response and lifetime of the electrodes and the effects of magnesium and sodium ions on the determination of 10−3−10−5 M calcium are examined in detail. The ionophore electrode is shown to be most satisfactory.

Packed microcapillary liquid chromatography with reduced I.D. columns

Abstract Packed microcapillary columns with internal diameters and particle size (silica gel) 30–40 μm and 10 μm, respectively, were prepared with the aim of reducing analysis time. The h–v relation for this microcapillary is similar to that of the microcapillary of 75 μm I.D. and particle size 30 μm, which has hitherto been thought to be the optimum. Initial results show that analysis time would be reduced to one-fifth. Applications for aromatic compounds were demonstrated. Combined loop and split injection was used. The reproducibility is good, and the operation simple.

The performance of a cadmium ion-selective electrode in metal buffer solutions and the determination of the stability constants of cadmium complexes

Abstract The potential response of a cadmium ion-selective electrode was examined in twelve metal buffer solutions. In the absence of ligands, Nernstian response down to 10−6 mol dm−3 was obtained between pH 4 and 8. in metal buffer solutions much lower concentrations could be measured, depending on the ligand and pH. The stability constants were determined successfully for cadmium complexes with various ligands: acetic acid, ammonia, glycine, iminodiacetic acid, ethylenediamine-N,N′-diacetic acid, nitrilotriacetic acid, N-hydroxyethylethylenediamine-N,N′,N′-triacetic acid (H3HEDTA), ethyleneglycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid (H4EGTA), 1,3-diaminopropan-2-ol-N,N,N′,N′-tetraacetic acid (H4DPTA), 2,2′-bipyridine, and 1,10-phenanthroline. In the cases of H3HEDTA, H4EGTA, H4DTPA, and H4EDTA(ethylenediamine-N,N,N′,N′-tetraacetic acid), the ion-selective electrode behaved abnormally under certain conditions. Critical conditions for the normal response of the ion-selective electrode are discussed.