Vol. 51 No. 10
October, 2002
Tomokazu Tajiri and Yutaka Itabashi*
*Laboratory of Bioresouces Chemistry, Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1, Minato-cho, Hakodate-shi, Hokkaido 041-8611
(Received 7 May 2002, Accepted 9 July 2002)A simple and sensitive method for the determination of molecular species of phosphatidylcholine (1,2-diacyl-sn-glycero-3-phosphocholine, PC) was develoved. Intact PC, which was isolated from soybean and salmon roe, was followed by reversed-phase high-performance liquid chromatography (HPLC) on a highly efficient ODS column (25 cm×4 mm i.d., 4 µm particle size) using methanol-acetonitrile-triethylamine (90:10:0.1, v/v/v) as the mobile phase, which gave a clear resolution of individual molecular species containing polyunsaturated fatty acids. Reversed-phase HPLC in conjunction with positive electrospray ionization mass spectrometry (ESI-MS) gave a weak [M-RCO+2Na]+ ion in addition to prominent pseudomolecular [M+H]+ and [M+Na]+ ions, by which individual molecular species could be identified.
Keywords : phosphatidylcholine; molecular species; soybean; salmon roe; reversed-phase HPLC; electrospray ionization mass spectrometry.
Ryo Horiguchi*, Isoshi Nukatsuka*, Yutaka Shimizu*, Shinya Sekikawa*, and Kunio Ohzeki*
*Department of Material Science and Technology, Faculty of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki-shi, Aomori 036-8561
(Received 30 April 2002, Accepted 8 July 2002)A cellulose nitrate resin (CNR) suspension was prepared by pouring a mixture solvent of dichloromethane and tetrahydrofuran (2:1) containing cellulose nitrate into an aqueous solution of benzalkonium chloride under vigorous stirring, volatilizing dichloromethane and tetrahydrofuran at about 98°C, and concentrating the suspension with by centrifugation. The resulting suspension was used for the solid-phase extraction (SPE) of thallium(III) in water. The surface of CNR was supposed to be positively charged because of a remaining benzalkonium ion. It was found that thallium(III) was extracted from dilute hydrochloric acid (pH 1.6) to CNR added as a resin suspension to a sample solution, presumably as its chloride complex. The presence of ammonium pyrrolidinedithiocarbamate improved the extraction yield. Thallium(I) was not extracted without the addition of bromine water. After SPE, CNR was collected on a membrane filter by filtration under suction, was suspended again in 1.0 ml of 10 mM HNO3 with ultrasonication, and then was injected directly into an electrothermal atomic absorption spectrometer. A linear calibration graph was obtained in the range 0~30 ng Tl(III) using 50 ml of a sample solution. The detection limit, based on three times the standard deviation of the blank, was 0.9 ng (18 pg ml-1). The repeatability was examined using 50 ml of a sample solution containing 30 ng of Tl(III). The relative standard deviation was 2.5% (n=5). The recovery of 30 ng of Tl(III) from 50 ml of a river water sample was 95±3% (n=3).
Keywords : thallium; electrothermal atomic absorption spectrometry; solid-phase extraction; cellulose nitrate; water.
Masakazu Minagawa, Takashi Hayashita, Qing Dai*, Richard A. Bartsch** and Norio Teramae*
*Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578
**Department of Chemistry and Biochemistry, Texas Tech University, Lubbok, Texas 79409 U.S.A.
(Received 2 May 2002, Accepted 14 June 2002)For selective PbII ion recognition, a novel podand fluoroionophore (PD-18C6) possessing a pseudo-18-crown-6 structure as a binding site and proton-ionizable N-dansyl acetamide as a photosignal transduction moiety has been designed. Examinations of the UV-Vis absorption, fluorescence, and excitation spectra in 70% 1,4-dioxane-30% water (v/v) by varying the solution pHs reveal that proton dissociation of the acetamide moiety induces an enhancement of the fluorescence emission with blue shifts of UV-Vis and fluorescence spectra. It is found that the proton dissociation of PD-18C6 is efficiently promoted by PbII binding, resulting in an emission response for PbII over the pH region from 4.0 to 5.0. 1H-NMR and IR analyses of PD-18C6/PbII complex support that PbII is incorporated inside the pseudo-18-crown-6 cavity of PD-18C6 by ion-exchange binding with the dansyl acetamide protons. To elucidate the metal ion selectivity, the fluorescence responses of PD-18C6 in 70% 1,4-dioxane-30% water (v/v) at pH 4.3 were examined in the presence of PbII, ZnII, CdII, and KI. The selective fluorescence emission response of PD-18C6 was only observed for PbII. These results demonstrate that PD-18C6 fluoroionophore has a potential to recognize PbII ion in aqueous sample solutions.
Keywords : podand structure; fluorescence response; lead ion; proton-ionizable polyethers; dansyl fluorophore.
Takeshi Shimada, Tokuo Shimizu and Nobuo Uehara*
*Department of Applied Chemistry, Faculty of Engineering, Utsunomiya University, 7-1-2, Yoto, Utsunomiya-shi, Tochigi 321-8585
(Received 15 May 2002, Accepted 3 July 2002)Thermo-sensitive copolymers of poly(N-isopropylacrylamide) having polyamino groups and carboxyl groups were synthesized. The aggregation properties of the thermo-sensitive copolymers were investigated in terms of the solution parameters, such as pH and the concentration of heavy metal ion. The distribution of biomolecules between the aqueous phase and the polymer phase mediated by phase transition was also considered. The lower critical solution temperatures (LCST) of the thermo-sensitive copolymers increased with an increase of pH of the solution. The responses of the synthesized thermo-sensitive copolymers were superior to that of poly(N-isopropylacrylamide) having only pH-responsible carboxyl groups. The addition of heavy metal ions into a polymer solution increased the LCST of the solution. Although the thermo-sensitive copolymers reacted with Cu2+ ion to form a blue complex, they released Cu2+ ions from aggregates by a phase transition. Anionic compounds tended to be distributed to the polymer aggregates, in contrast with cationic compounds which were not distributed to the polymer phase.
Keywords : poly(N-isopropylacrylamide); thermo-sensitive; pH-sensitive; distribution of biomolecules; polyamino; carboxyl.
Kazunari Mitsuhashi, Ryozo Yoshizaki*, Takeshi Ohara and Hitoshi Wada**
*Graduate School of Pure and Applied Sciences, The University of Tsukuba, 1-1-1, Tennodai, Tsukuba-shi, Ibaraki 305-8573
**National Institute for Materials Science, 3-13, Sakura, Tsukuba-shi, Ibaraki 305-0003
(Received 30 April 2002, Accepted 5 July 2002)The control of the retention and separability of samples in high performance liquid chromatography (HPLC) systems is difficult, and usually requires exchanging the mobile phase and/or the column. To develop a separation system that does not require regularly exchanging them, we developed a magnetic chromatography (MC) system that uses a continuous-flow system to separate multiple ionic species with different magnetic properties. To experimentally demonstrate the feasibility of such an MC system, we measured the retention of ions in the MC system for aqueous solutions of either pure I-, CuII, NiII, CrIII or CoII ions. We used two trial magnetic columns in which thin ferro-magnetic alloy ribbons were arranged parallel or vertical to the flow on the upper and bottom walls, and thereby high-gradient magnetic fields were generated in the columns. We coined parallel and vertical types for these columns. External magnetic fields were applied and varied from 0 to 3 T to an aqueous solution of transition element cations and anions flowing in an MC system. We demonstrated that the retention time was delayed about by 20 or 40 minutes, and that for the CoII ion the chromatogram broadened with increasing the applied magnetic field intensity (H). Furthermore, our results suggest that for ionized transition elements with a larger Bohr magneton number, the retention time becomes longer. We experimentally derived a retention factor (k), that can be simply expressed in terms of an MC parameter (pMCH), which is the product of the Bohr magneton number, the concentration of ions, and H. When we used the parallel type column, the MC parameter could be used to correlate all of the experimental data in terms of k, as k = 0.0014, pMCH1.47. Hence, k is proportional to about the 3/2 power of the MC parameter. When we used the vertical type column, the k deviated from this curve under four experimental conditions out of ten, but k = 0.002, pMCH1.52 was obtained. From these experiments we confirmed that there is a significant effect of high-intensity, high-gradient magnetic fields on the behavior of paramagnetic cations in water.
Keywords : magnetic chromatography; high-intensity and high-gradient magnetic field; superconducting magnet; Bohr magneton number; transition element ion.
Yuji Miyaguchi, Akira Kotani and Fumiyo Kusu*
*School of Pharmacy, Tokyo University of Pharmacy and Life Science, 1432-1, Horinouchi, Hachioji-shi, Tokyo 192-0392
(Received 27 April 2002, Accepted 26 July 2002)High-performance liquid chromatography with electrochemical detection (HPLC-ECD) based on the reduction reaction of quinone was used to determine lactic acid in human blood. The peak area of the current signal (charge) was proportional to the amount of lactic acid, ranging from 0.1 nmol to 40 nmol (r>0.999). Standard lactic acid at 10 nmol was determined ten times with a relative standard deviation (RSD) of 1.18%. The detection limit (S/N=3) was 0.04 nmol. The concentration of lactic acid in plasma collected from a volunteer after 14 hours of fasting and 1 hour after eating a meal obtained by the present method were 1.26 mM and 2.32 mM, respectively. The RSD (n=5) was 3.6% or less and the recovery was 94% or more. The concentrations were identical with those obtained by a commercial lactic acid determination kit (F-kit, DL-lactic acid), which a required ten-times larger sample volume than that for the present method. The present method is useful for analyzing of the lactic acid for studying the circulatory system and a metabolism system.
Keywords : HPLC-ECD; quinone; determination; lactic acid in human plasma.
Mikako Nakashima, Masao Kosaka and Hideki Monma*
*Kogakuin University, 2665-1, Nakano-cho, Hachioji, Tokyo 192-0015
(Received 30 April 2002, Accepted 2 August 2002)We had developed the method for measurement of surface roughness using X-ray diffractometer. This method uses the X-ray diffraction (XRD) profiles from the ""surface-replicated film"" instead of that from the sample itself, which is vaccum-metallized thin metal film on the surface of a sample to replicate surface roughness. Several peaks separated from this profile are calculated exactly to obtain diffraction angle 2q, intensity I, integrated intensity S, full width at half maximum intensity w (F.W.H.M.), and some other parameters. Decentering distance x as the height of convexity (x>0) or as the deepness of concavity (x<0) is calculated by the deviation of diffraction angle Δ2θ, and area of "rough" surface is calculated by the integrated intensity. Analytical result of the distance and area is described by these analyzed parameters like an irregular stairway. We studied for measurement to fix particularly appropriate conditions. Consequently, we designated these conditions to measrue surface roughness as follows: surface-replicated film is Au (gold), target is Cu (copper), divergence slit and scattering slit are 1° (X-ray exposed area: 16.2 mm×10.0 mm), receiving slit is 0.3 mm. Then, we measured of electrodeposited hydroxyapatite samples using these compiled conditions. Analytical result of these samples was lead statistically and we were able to find rough surface of electrodeposited cathodes, particle size of deposited hydroxyapatite crystal on the cathodes, and convex area of electrodeposited samples by these data. Though the SEM micrograph gives figures and sizes of samples, it transcribes a fraction of the sample in a vacuum showed narrow than our X-ray diffraction method in air. If you know the surface of samples by SEM as wide as by our method, you will spend over twenty hours for only one or a few of sample. But we can need only 60~120 minutes for measurement of one sample.
Keywords : X-ray diffraction method; surface roughness; peak-separation; surface-replicated film; SEM.
Shinpei Tsusima, Izuru Matsubayashi and Yuko Hasegawa*
*Department of Chemistry, Faculty of Science, Science University of Tokyo, 1-3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601
(Received 2 May 2002, Accepted 8 July 2002)In order to study the effect of the Lewis acidity of solvents on extractability, the hydration number of the extracted species and the interaction between the solvents and phen were examined in the extraction of europium(III) with pivaloyltrifluoroacetone (PTA, HA) and/or 1,10-phenanthroline (phen, B) into dichloromethane, chloroform and pentachloroethane. In organic solvents, the water molecules coordinated to EuA3 are replaced with phen to form phen complexes: EuA3·n0H2O(o)+B(o) ⇔ EuA3·B(o)+n0H2O(o). The equilibrium constants are similar among organic solvents where the solvent-solute interaction is not significant. However, the value of K decreased in the sequence CH2Cl2>CHCl3>C2HCl5. The IR spectra in carbontetrachloride containing the respective solvents showed a peak at 2987 cm-1 for C2HCl5, at 3019 cm-1 for CHCl3, at 3049 cm-1 and 2984 cm-1 for CH2Cl2, while in the presence of phen the peak shifted at 2919 cm-1 for C2HCl5 and 2967 cm-1 for CHCl3, and no change in CH2Cl2. The difference of the K values among the three solvents used in the present study is explained in terms of the different Lewis acidity, which was indicated by the download shift: CH2Cl2<CHCl3<C2HCl5.
Keywords : europium(III) chelate; 1,10-phenanthroline; adduct formation constants; water in organic solvents; solvent-solute interaction.
Junichi Iwata, Masayuki Itagaki and Kunihiro Watanabe*
*Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641, Yamazaki, Noda-shi, Chiba 278-8510
(Received 14 May 2002, Accepted 31 July 2002)The indium-2,2'-bipyridine complex excited by UV ray fluoresces in an aqueous solution. The fluorescence intensity of the complex has been weak. However, the fluorescence intensity of 2,2'-bipyridine as a detection reagent was remarkably lower compared with that of the In-bpy complex. Assuming the fluorescence intensity of the reagent blank to be lower than that of the analyte, the reagent is useful for determining the complex by enhancing the sensitivity of the fluorometer. Therefore, the conditions for determining indium has been examined in detail by fluorometry in an aqueous solution. As a result, indium could be determined over the range from 15 to 500 ng ml-1 by measuring the fluorescence intensity of a complex obtained at pH 6.0, bipyridine 6.4×10-5 M, and a standing time of 15 min. The excitation and fluorescence wavelength for measuring the complex were 303 nm and 330 nm, respectively. 3D-spectra were measured in order to examine the component ratio of the complex obtained under various conditions. The 1:2 complex (metal:ligand) was not confirmed by the 3D-spectra and continuous variation method. Indium reacted instantly with 2,2'-bipyridine to form an unstable 1:1 complex in an aqueous solution. Therefore, the determination of indium was studied based on a flow injection analysis (FIA), rather than a batch method. The detection limit of indium was improved to 2.6 ng ml-1 by FIA at sample solution flow rate of 0.8 ml/min; that of bipyridine was 1.4 ml/min. Further, 120 samples were determined per one hour by FIA. The sample volume used by FIA was 80 µl. The fluorescence quantum yield of the In-bipyridine complex was 0.17 (that of bipyridine, 0.018). Ga, Al, Zn, Cd and Tl interfered with the determination of indium, owing to their fluorescence of the complexes formed with 2,2'-bipyridine.
Keywords : 2,2'-bipyridine; indium; fluorometry; flow injection analysis; 3D-spectrum.
Yuko Gorai, Koichi Oguma* and Yu Komatsu**
*Department of Materials Technology, Faculty of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba-shi, Chiba 263-8522
**Department of Environmental System Engineering, Faculty of Engineering, Kanazawa Institute of Technology, 7-1, Ogigaoka, Nonoichi-cho, Ishikawa 921-8501
(Received 30 April 2002, Accepted 9 July 2002)Eporous AS-4 (Miyoshi Oil & Fat Co.) is the trade name given to an arsenic-selective chelating resin of an iminodiacetate polystyrene-divinly benzene copolymer type, which has been modified by successively treating with iron(III) and sodium hydroxide solutions. Iron(III) hydroxide in Eporous AS-4 was removed by washing with 3 mol/l hydrochloric acid to prepare plain Eporous AS-4. The distribution coefficients for CaII, CdII, CoII, CuII, FeIII, MgII, NiII,and ZnII on plain Eporous AS-4 were measured by a batch method as a function of the hydrochloric acid concentration, and compared with those on other commercially available chelating resins, i.e., Chelex 100 (Bio-Rad Laboratories) and Diaion CR11 (Mitsubishi Chemicals Co.). The distribution coefficients for CuII on plain Eporous AS-4 are higher than those on Chelex 100 and Diaion CR11 by a factor of ca.100 in hydrochloric acid media of less than 0.1 M. The selective adsorption of CuII and FeIII on plain Eporous AS-4 has been successfully applied to the separation of copper and iron in high-purity zinc certified reference materials prior to their measurements by flame atomic absorption spectrometry.
Keywords : chelating resin; copper; iron; high-purity zinc; separation.
Kazuhisa Sugiyama, Takaya Takei, Kayo Tachibana and Yoshinori Sugitani*
*Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya 2946, Hiratsuka-shi, Kanagawa 259-1293
(Received 23 April 2002, Accepted 29 July 2002)Saccharides have many hydroxyl groups in their molecular formulas and show mutarotation in aqueous solutions. Because of this, during the α,β isomerization of a D-glucose solution, a rearrangement of hydration occurs around the D-glucose molecules based on a stereochemical change of OH(1). High-frequency spectroscopy is an analytical method which is sensitive to the solution structures and/or a change of state of association between molecules. We applied the high-frequency method to the study of the α,β isomerization of D-glucose. The absorption intensity around 1800 MHz of high-frequency spectra was found to decrease with the progress of the isomerization reaction of D-glucose. The decrease of the intensity showed a linear relation with the reaction time. These results were found to agree with the rate of the reaction obtained from a rotation-angle measurement.
Keywords : D-glucose; high-frequency spectroscopy; isomerization; rearrangement of hydration; optical rotation measurement.
Tomohiro Kageyama and Masataka Hiraide*
*Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603
(Received 27 March 2002, Accepted 6 July 2002)A chelating agent-impregnated w/o emulsion was prepared by dissolving 50 mg of 8-quinolinol and 0.15 ml of Span-80 (nonionic surfactant) in 5 ml of toluene and then mixing with 1.5 ml of 1 mol/l hydrochloric acid by ultrasonic irradiation (20 kHz) for 15 s. The resulting emulsion was added to 25 ml of a sample and dispersed by stirring for 5 min as numerous small globules (0.1~0.5 mm in diam.). Copper(II) ions in the sample were quantitatively diffused through the toluene layer into small droplets of hydrochloric acid at pH 3~7. The emulsion was separated and heated at 80~90°C to segregate the aqueous (hydrochloric acid) and organic (toluene) phases. The copper in the aqueous phase was determined by graphite-furnace atomic absorption spectrometry. The recovery of copper(II) in the presence of iron(III) was successfully achieved with a yield of greater than 95% at pH 3~3.5, where the iron(III) existed as colloidal hydroxide particles and did not penetrate into the emulsion. This discrimination may be attributed to the surfactant layer at the oil-water interfaces. At higher pH's, however, the iron(III) colloids coagulated to form bulky hydroxide precipitates, on which most of the copper(II) ions were coprecipitated. The proposed emulsion method has been applied to the determination of copper at low mg/g levels in high-purity iron metals.
Keywords : emulsion; 8-quinolinol; copper; high purity iron; preconcentration.
Kazuyoshi Higuchi, Tohru Saitoh and Masataka Hiraide*
*Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603
(Received 30 April 2002, Accepted 4 July 2002)Unilamellar vesicles (i.e., liposomes) having 0.4 µm diameters were prepared by an extrusion technique. The liposomes were composed of phosphatidylcholine, phosphatidylglycerol, cholesterol, and chelating agents. When liposomes containing 8-hydroxyquinoline (HQ) were added to a water sample, copper(II) ions were collected with a recovery of 76±3%. The recovery, however, was decreased to 44 or 30% when the sample contained 1 or 5 µg/ml of humic acid, respectively. This was probably due to the exclusion of the copper-humin complex from the surface of liposome. A selective uptake of free copper(II) ion was not achieved by other chelating agents (e.g., 1,10-phenanthroline and N-benzoyl-N-phenylhydroxylamine). The inclusion of (N-ditiocarboxy)sarcosine in the inner water pool of the liposome significantly enhanced the copper uptake, while maintaining the selectivity.
Keywords : copper(II); selective uptake; humic acid; liposome; 8-hydroxyquinoline.
Masakazu Hasegawa*, Noriaki Furukawa*, Tetsuyoshi Naito** and Hiromichi Yamada*
*Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya-shi, Aichi 466-8555
**Fuji Chemical Co., Ltd., Nakagaito, Nasubigawa, Nakatsugawa-shi, Gifu 509-9132
(Received 30 April 2002, Accepted 23 July 2002)Chlorinated hydrocarbons represented by chloroform and aromatic solvents, such as benzene and toluene, should be voluntarily refrained from use as much as possible, while taking account of the preserving the natural environment and carcinogenic activity. From these points of view, in order to develop a less toxic solvent which can be a useful substitute solvent for chloroform, benzene, toluene, etc., we took notice of mixed solvents consisting a solvating solvent, alcohols and a non-solvating solvent, alkanes, as a less toxic solvent. The ion-pair extraction of the 8-quinolinol-5-sulfonate anion with a tetrabutylammonium cation was carried out using 1-nonanol/octane mixed solvents with a variety of mixing ratios. The formation, partition and extraction constants of the ion-pair of the 8-quinolinol-5-sulfonate anion with a tetrabutylammonium cation were estimated by a slope analysis and a curve-fitting method. The ion-pair formation constant in the aqueous phase was found to be dependent on the mixing ratio of the solvents. The sulfonate group can be expected to be solvated by three 1-nonanol molecules in the aqueous phase. The present results suggest that the 1-nonanol/octane mixed solvents are also useful not only for ion-pair extraction, but for analyzing the mechanism of ion-pair extraction.
Keywords : ion-pair extraction; 1-nonanol/octane mixed solvent; solvation; 8-quinolinol-5-sulfonic acid; tetrabutylammonium cation.
Ikuhiro Matsuoka*, Tetsuyoshi Naito** and Hiromichi Yamada*
*Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya-shi, Aichi 466-8555
**Fuji Chemical Co., Ltd., Nakagaito, Nasubigawa, Nakatsugawa-shi, Gifu 509-9132
(Received 30 April 2002, Accepted 24 July 2002)The ET values, which show the acceptability of solvents for a number of solvents saturated with water, were estimated and the solubility of water in these solvents were coulometrically measured using the Karl-Fischer method. The solvents were seven kinds of alkanes, three kinds of aromatic solvents, three kinds of chlorinated hydrocarbons, four kinds of esters, six kinds of ketones, and five kinds of alcohols. The ET values were found to correlate closely with the solubility of water in those solvents, expect for 1,2-dichloroethane. The solubility of water in some of these solvents was significantly interrelated with the various equilibrium constants in the extraction of copper (II) with decanoic acid using these solvents. It was suggested that the extraction is influenced by hydration. The solubility of water in the present solvents ranged widely from 2.36×10-3 to 4.74 mol dm-3 compared with the short range of the ET values. It is expected to be useful for investigating of solvent effects on the solvent extraction as a sensitive property for an organic solvent.
Keywords : solubility of water in organic phase; ET value; hydration; Karl-Fischer; solvent extraction.
Ikuhiro Ikeda*, Satoshi Tsukahara*, Hideaki Monjushiro* and Hitoshi Watarai*
*Department of Chemistry, Graduate School of Science, Osaka University, 1-1, Machikaneyama-machi, Toyonaka-shi, Osaka 560-0043
(Received 30 April 2002, Accepted 3 July 2002)We have studied a laser ablation method for the fabrication of planar quadrupole and octapole microelectrodes which can be used in the dielectrophoresis (DEP) of micro particles. A gold layer 225 nm in thickness was formed on a glass plate by vapor deposition in vacuo. Pulsed laser light (355 nm, 14 µJ/pulse) was focused on the plate as a spot of 1 µm×1 µm with an objective (50×) to remove the gold on the plate by laser ablation. The plate was placed on an xy stage, whose motion was controlled by 1 µm steps with a personal computer to fabricate patterns of quadrupole and octapole electrodes. The working area of the electrodes was 50 µm in radius for both fabricated electrodes. Polystyrene particles (0.53 µm in radius) in water were employed as a test sample. “Positive DEP”, the migration to an area of stronger electric field, and “negative DEP”, the opposite migration were observed at the lower (1~100 kHz) and higher (1~10 MHz) frequencies, respectively, regardless of the shape of the electrode. They migrated in the radial direction in the working area. The DEP velocity of the particles depended on their position; their migration became faster as they approached the electrode, and vice versa. The DEP migration of the particles in the octapole electrode was faster than that in the quadrupole one at the same position, as expected from a calculation of the electric field strength. A theoretical equation was derived based on the concept that a dielectrophoretic force on the particles was equalized to a frictional force on it in water. The DEP trajectory of the microparticles agreed well with the theoretical equation. Thus, the planar multipole microelectrodes fabricated by the present method was confirmed to work effectively as electrodes in dielectrophoresis.
Keywords : dielectrophresis; octapole microelectrode; quadrupole microelectrode; laser ablation; vapor deposition of gold.
Minori Tamagawa, Hideaki Monjushiro and Hitoshi Watarai*
*Department of Chemistry, Graduate School of Science, Osaka University, 1-1, Machikaneyama-machi, Toyonaka-shi, Osaka 560-0043
(Received 30 April 2002, Accepted 6 July 2002)Laser-photophoresis is a new technique which can be used to characterize and separate microparticles in a liquid or gas. We developed an experimental apparatus to measure the photophoretic velocity of microparticles in a liquid under a microgravity condition. The apparatus was composed of a cw Nd: YAG laser (532 nm), a microscope, a CCD system, and a remote controlled sample stage and was set in a capsule which was used for a free-fall experiment. All of the experimental operations were made externally using a personal computer. The photophoretic behavior of micrometer-sized carbon particles dispersed in water were observed by using the apparatus under microgravity. A precise determination of the photophoretic velocity was achieved under a microgravity experiment because both the density difference between the carbon and water and the natural convection due to heat generation on the laser irradiation disturb a measurement of the photophoretic velocity. The photophoretic efficiency of the carbon microparticle was derived from the observed velocity and compared to those for transparent microparticles. It has been elucidated that the photophoretic efficiency of the carbon microparticle is much greater than those of transparent microparticles, such as polystyrene spheres. Also, the photophoretic behavior of the carbon microparticles under normal gravity was examined and compared to that observed under microgravity. The effect of natural convection on the photophoretic velocity under the normal gravity condition was revealed.
Keywords : radiation pressure; microgravity; photophoresis; continuous wave laser; spherical particle.
Masato Ueda, Akiyo Komai, Keiichi Fujimori, Takayo Moriuchi-Kawakami and Yasuhiko Shibutani*
*Department of Applied Chemistry, Faculty of Engineering, Osaka Institute of Technology, 5-16-1, Omiya, Asahi-ku, Osaka 535-8585
(Received 26 April 2002, Accepted 24 July 2002)A poly(vinyl chloride)(PVC) membrane electrode based on N,N'-bis(2'-hydroxyimino-1'-phenylpropylidene)-1,3-propane-diamine, PHO3 (previously reported), showed excellent performance as a silver(I) ion sensor. The lifetime of this electrode was about 20 days. Therefore, to improve the lifetime for a dioxime-type Schiff based PVC membrane electrode, three kinds of PHO3 derivatives (PHEtO3, PHPrO3, and PHBuO3) that converted the PHO3 methyl group with ethyl, propyl or butyl group were synthesized, respectively. These Schiff bases (PHEtO3 and PHPrO3) gave good performance with a near-Nernstian response, 45~51 mV decade-1, in the Ag+ activity range from 5.0×10-7 to 7.9×10-2 M. The Ag+ selectivity values with respect to K+, -log KpotAg,K were 4.35 and 4.30 (fixed interference method). Among the these tested Schiff bases, a N,N'-bis(2'-hydroxyimino-1'-phenylbuthylidene)-1,3-propane-diamine(PHEtO3) based NPOE(plasticizer) -KTpClPB (anion excluder) system electrode showed superior performance during an observation period of more than 2 months, though the Ag+ selectivity coefficient with respect to K+,-log KpotAg,K was reduced from 4.35 to 2.95 due to the hydrolysis of Schiff bases.
Keywords : dioxime type Schiff base; silver ion selective electrode; lifetime of PVC membrane electrode; selectivity coefficient.
Kazuhiro Nomura, Mitsuko Oshima, Toshio Takayanagi and Shoji Motomizu*
*Department of Chemistry, Faculty of Science, Okayama University, 3-1-1, Tsushimanaka, Okayama 700-8530
(Received 2 May 2002, Accepted 29 July 2002)Water-soluble fluorescent reagents, 1,8-di-(toluene-4-sulfonylamino)-naphthalene-3,6-disulfonic acid (BTND) and 1,8-di-(trifluoromethanesulfonylamino)-naphthalene-3,6-disulfonic acid (BTFND), were newly synthesized. The reactivities of these fluorescent reagents to Cu2+, Ni2+, Co2+, Cd2+, Pb2+, VV, Ag+, Fe3+, and Mg2+ were examined. BTFND was reacted with 8 metal ions, except for Pb2+, to show fluorescence quenching. BTND was selective to Cu2+, and the fluorescence was quenched quantitatively at pH 7 in an aqueous solution (λex=360 nm and λem=405 nm). The calibration graph for Cu2+ with BTND was rectilinear over the concentration range from 0 to 10-5 M and the detection limit was 2.0×10-7 M. BTND has many advantages, such as selectivity for Cu2+, high sensitivity, and a simple procedure.
Keywords : determination of copper ion; 1,8-di-(toluene-4-sulfonylamino)-naphthalene-3,6-disulfonic acid; 1,8-di-(trifluoromethane-4-sulfonylamino)-naphthalene-3,6-disulfonic acid; fluorescence detection.
Takuji Kagawa, Toshio Takayanagi, Mitsuko Oshima and Shoji Motomizu*
*Department of Chemistry, Faculty of Science, Okayama University, 3-1-1, Tsushimanaka, Okayama-shi, Okayama 700-8530
(Received 2 May 2002, Accepted 30 July 2002)2-(5-Nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino) phenol (Nitro-PAPS) was used for a quantitative determination of ultratrace-level metal ions in commercially available metal salts by capillary zone electrophoresis. At pH 7, Nitro-PAPS reacts with various metal ions to form chelate compounds having large molar absorptivities. Although chelate formation is useful for the highly sensitive detection of metal ions, the resolution of the metal complexes is poor at pH 7. Cetyltrimethylammonium bromide was added to suppress any electroosmotic flow. The hydration of nitro groups of a chelating agent and chelates was controlled by the addition of urea. Sodium sulfate was also utilized to sharpen the signals of metal chelates by a field-enhanced stacking effect. As a result, the resolution was improved and the determination of 10-7 M level metal ions was possible. The proposed method was applied to the analysis of metal impurity at ultratrace levels in commercially available nickel and iron salts.
Keywords : capillary zone electrophoresis; metal ions; 2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol; nickel and iron salt; impurity analysis.
Hironobu Takahashi*, Yasuro Niidome and Sunao Yamada**
*Department of Materials Physics and Chemistry, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581
**Department of Applied Chemistry, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581
(Received 7 May 2002, Accepted 6 July 2002)Gold particles were deposited on a cover glass by pulsed-laser irradiation of thiol-capped gold nanoparticles in cyclohexane. Dodecanethiol (DT) was used as the capping agent to stabilize colloidal dispersion of the gold nanoparticles in cyclohexane (DT-capped gold nanoparticles: DTAu). The DT molecules adsorbed on the DTAu were partially replaced with 1,6-hexanedithiol (HD) to obtain photoreactive gold nanoparticles (HDAu). A hydrophilic cover glass was immersed into the cyclohexane solution of HDAu or DTAu, and irradiated by the pulsed 532 nm light (10 Hz, 33 mJ/pulse) of a Nd : YAG laser, resulting the deposition of gold nanoparticles on the cover glass. The degree of deposition was traced by absorption spectroscopy. The amount of deposited gold particles was evaluated from ICP-MS after dissolving them into aqua regia. More than 2 min of irradiation was necessary for the deposition of DTAu, while only 1 min of irradiation resulted in the deposition (~3 µg) of HDAu. It was found that partial replacement of DT with HD accelerated the laser-induced deposition of the gold nanoparticels as well as their size growth.
Keywords : gold nanoparticles; laser-induced deposition; scanning electron micrograph; ICP-MS.
Kenji Koyanagi and Masaaki Tabata*
*Department of Chemistry, Faculty of Science and Engineering, Saga University, 1 Honjo-machi, Saga-shi, Saga 840-8502
(Received 5 June, 2002, Accepted 24 July, 2002)2,3,7,8,12,13,17,18-Octafluoro-5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (F28 tetraphenylporphyrin; OFTPFPP) was synthesized by the condensation of 3,4-difluoropyrrole and pentafluorobenzaldehayde. 3,4-Difluoropyrrole was prepared from 2,2,3,3-tetrafluorosuccinic acid as the starting material through 5-step reaction processes. The acid-dissociation constants of OFTPFPP were determined by a solvent-extraction method in the presence of tetrabutylammonium chloride (0.1 mol dm-3). The 28 fluoro atoms decreased the basicity of the porphyrin and made two protons of imidazoles release at pH 4 and 7 ((H2)o+Na+ ⇔ [(HP-) (Na+)]o, pKa3 4.2; [(HP-)(Na+)]o+Na+ ⇔ [(P2-)(Na+)2]o, pKa4 8.0). The protons of the tetrephenylporpyrin unsubstituted by fluorine atom did not dissociate at a pH lower than 14. OFTPFPP reacted with lithium ion in the neutral pH range, and gave a new absorption spectrum with a maximum wavelength of 416 nm in chloroform.
Keywords : synthesis of fluoroporphyrin; lithium ion; separation; spectrophotometry; detection.
Hiroaki Sakamoto and Hiroshi Nakamura*
*Faculty of Pharmaceutical Sciences, Science University of Tokyo, 12, Ichigaya-funagawara-machi, Shinjuku-ku, Tokyo 162-0826
(Received 7 May 2002, Accepted 30 July 2002)The purpose of this study is to develop a simple method for detection of genetically modified soybean(GMS), Roundup Ready®(Monsanto company), a herbicide-tolerant soybean, in which 5-enolpyruvylshikimate-3- phosphate synthase(EPSPS) gene has been replaced by herbicide-tolerant gene(CP4EPSPS). DNAs extracted from soybean samples were amplified by polymerase chain reaction and analyzed by agarose gel electrophoresis. As the result, the CP4EPSPS gene was successfully detected as SYBR Gold®-stained fluorescent band whose concentration was almost proportional to the concentration of GMS in the sample. By applying this method to processed foods of soybeans, the temperature and the time of heating process were proved to influence on the detectability of the CP4EPSPS gene, probably by shortening the DNA molecule.
Keywords : genetically modified soybean(GMS); polymerase chain reaction(PCR); agarose gel electrophoresis; herbicide-tolerant soybean; 5-enolpyruvylshikimate-3- phosphate synthase(EPSPS); EPSPS synthase from Agrobacterium strain CP4(CP4EPSPS).
Mikio Koyama* and Tatsuhiko Tanaka*
*Faculty of Engineering, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601
(Received 30 April 2002, Accepted 16 July 2002)A simple electrolytic preconcentration technique is described for the simultaneous determination of trace amounts of zinc, copper, lead and bismuth in high-purity aluminum by inductively coupled plasma-mass spectrometry (ICP-MS). The technique is based on the electrochemical deposition and dissolution of trace elements. The optimized operating conditions were as follows: the desired trace metal ions in 1 ml of a diluted hydrochloric acid solution (pH=2.3) were deposited in a mercury-plated glassy-carbon electrode (surface area of about 2 cm2) as metals at -1.30 V vs. SCE for 90 min; the resulting deposits were then anodically dissolved in another solution (1 ml of 0.1 M nitric acid) at 0.10 V vs. SCE for 1 min. After electrolytic separation, the concentrations of the desired elements were determined by ICP-MS. Deposition yields greater than 97% were generally obtained in the presence of 2 mg ml-1 aluminum(III). The calibration graphs of the desired elements were linear with relative standard deviations (n=5) of less than 5.7% at the 2 ng ml-1 level for each of the elements. The possible interferences have been evaluated. The minimum limits of determinations (10σ) of zinc, copper, lead and bismuth in aluminum, calculated from repeated measurements (n=10) of a blank solution, were approximately 0.35, 0.18, 0.05 and 0.03 µg g-1, respectively. The proposed method was successfully applied to the determinations of zinc, copper, lead and bismuth at the µg g-1 level or lower in two high-purity aluminum samples. The time required for an analysis was within 3 h.
Keywords : zinc, copper, lead and bismuth determination; aluminum analysis; electrochemical deposition and dissolution of trace elements; electrolytic preconcentration technique; ICP-MS.
Hiroyuki Kurogouchi, Hideo Hayashi, Tomokazu Tanaka and Masataka Hiraide*
*Department of Molecular Design and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi, Aichi 464-8603
(Received 26 April 2002, Accepted 13 July 2002)ICP-MS combined with electrothermal vaporization (ETV) has excellent absolute detection limits, and hence allows the determination of trace elements in very minute amounts of samples. In the present work, ETV/ICP-MS was applied to the analysis of human hair for As and Se. A 0.50-mg weight of a sample was decomposed with 10 µl of 14 mol l-1 HNO3 and 2 ml of 30% H2O2 in a PTFE high-pressure decomposition vessel. The resulting solution was mixed with 25 µl of a 1 µmol l-1 KMnO4 solution and evaporated to dryness. The residue was dissolved in 500 µl of 1 mol l-1 HNO3, and a 5-ml aliquot of the solution was placed on a tungsten filament. After drying the sample electrically, the filament was rapidly heated to ca. 2500°C by discharging a high-capacity condenser (0.54 F). The sample plume generated from the filament was transported to the plasma with a stream of argon and the signal intensities of 75As+ and 82Se+ were measured by MS. The addition of KMnO4 to the sample was essential for preventing serious losses (30~50%) of analytes during evaporation. The accuracy of the proposed method was evaluated by analyzing a certified reference material (As 0.31±0.02 µg g-1, Se 2.0±0.08 µg g-1). The results (n=4) were in good agreement with the certified values: 0.30±0.01 µg g-1 for As and 2.0±0.2 µg g-1 for Se.
Keywords : ICP-MS; electrothermal vaporization; human hair; arsenic; selenium.
Hiroki Koga* and Michiko Ogata**
*Fukuoka Industrial Technology Center, Mechanics & Electronics Research Institute, 3-6-1, Norimatsu, Yahatanishi-ku, Kitakyushu-shi, Fukuoka, 807-0831
**Fukuoka Industry, Science & Technology Foundation, Acros Fukuoka Nishi Office 9F, 1-1-1, Tenjin, Chuo-ku, Fukuoka-shi, Fukuoka, 810-0001
(Received 14 May 2002, Accepted 12 July 2002)An new calibrating technique "Quartz Cell Method" was developed to determine trace amounts of carbon in steels by a high-frequency combustion-infrared absorption method. Sucrose was used as a primary standard. The Quartz Cell Method was free from contamination by carbon, and the obtained calibration curve showed good linearity, which passed through the origin. On the other hand, the pretreatment technique for the steel analysis was examined in order to remove of the contamination in the crucibles, accelerators and samples. Accordingly, the calibration curve obtained by steel CRMs with the pretreatment technique using pre-heating agreed well with that obtained by the present method. It was clarified that Quartz Cell Method can be applied as a calibrating technique for trace carbon determination in steels.
Keywords : determination of trace amounts of carbon; calibration method; infrared absorption method after combustion; chemical standard; sucrose; pretreatment method for trace carbon.
Takashi Kurasawa*,****, Takao Yotsuyanagi*,*****, Emiko Kaneko, Shingo Saito**, Suwaru Hoshi and Kunihiko Akatsuka***
* Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Sendai 980-8579
**,*** Department of Applied and Environmental Chemistry, Kitami Institute of Technology, Kitami-shi, Hokkaido 090-8507
**** Current address: The Nomura Securities Co. Ltd., 2-2-2, Otemachi, Chiyoda-ku, Tokyo 100-8130
***** Current address: Miyagi National College of Technology, Natori-shi, Miyagi 981-1239
(Received 12 April 2002, Accepted 2 July 2002)The retention behavior of cationic aluminium chelate with o,o'-dihydroxyazobenzene (DHAB or H2L), [AlL]+, in high-performance liquid chromatography (HPLC) was investigated using the C18-bonded silica stationary phase. In this study, it was found that when the pH of the mobile phase was 5.5, a significant tailing of the alminium chelate was observed, whereas when the pH was 2, a marked improvement of the elution was attained. These results were interpreted in terms of a silanol masking effect: when an acidic mobile phase is employed, protonation of the silanol groups on the surface is maintained, while eliminating the strong interaction between the cationic chelate and the stationary phase. The addition of sodium chloride in the eluent can also be used to eliminate peak tailing of the cationic chelate. Based on these results, the underlying immobilization mechanism of the aluminium chelate on the C18-bonded silica thin layer is explained by an electrostatic interaction between the cationic aluminium chelate and deprotonated silanol groups on the solid surface. The example in this study should provide valuable information to improve the separation quality of cationic solutes in HPLC.
Keywords : aluminium chelate; o,o'-dihydroxyazobenzene; HPLC; C18-bonded silica; silanol effect.
Shingo Arasaka, Emiko Kaneko, Shingo Saito, Suwaru Hoshi and Kunihiko Akatsuka*
*Department of Applied and Environmental Chemistry, Kitami Institute of Technology, Kitami-shi, Hokkaido 090-8507
(Received 30 April 2002, Accepted 18 July 2002)The thin-layer chromatographic behavior of a lanthanum-alizarin complexone (ALC)-fluoride complex was investigated with particular interest being paid to the separation of the ternary complex from La-ALC. Although the spectral shift of the La-ALC chelate upon binding to the fluoride ion is widely used for the spectrophotometric determination of fluoride ion, there do not appear to be any reports on thin-layer chromatography (TLC) for the ternary complex (La-ALC-F). In this study, it was found that when developed with 60% ethanol on a C18-bonded silica thin-layer plate, the ternary complex was easily eluted, forming a sharp band. Conversely, the La-ALC chelate was immobilized at the spotting position as a fleck. Furthermore, when a bluish-purple band was separated from a reddish-purple fleck, the ternary complex faded in a few minutes, whereas, when the band remained inside the fleck, no fading took place. These results are interpreted in terms of the dissociation of the labile complex caused by separation from the excess reagent. Consequently, the concentration of the La-ALC-F band across the center of the fleck provides a sensitive visualization of the fluoride ion down to 0.1 ppm.
Keywords : fluoride ion; alizarin complexone; lanthanum; C18-bonded silica; thin layer chromatography.
Ayako Yamazaki*, Yohichi Ishibashi**, Limin Yang*, Yoko Aiba* and Kin-ichi Tsunoda*
*Department of Chemistry, Faculty of Engineering, Gunma University, 1-5-1, Tenjin-cho, Kiryu, Gunma 376-8515
**Kohkankeisoku Corporation, 1-1, Minamiwatarida, Kawasaki-ku, Kawasaki, Kanagawa 210-0855
(Received 22 April 2002, Accepted 21 June 2002)The Methylene Blue extractive spectrophotometric method is a simple analytical method for boron and has been adopted as a JIS method for the determination of boron in steel samples. However, 1,2-dichloroethane, which is used in the method as an extraction solvent, is now one of the items of Environmental Quality Standards for water pollutants in Japan, and its use is severely restricted. Thus, we developed a Rhodamine 6G extractive spectrophotometric method of boron in steel to replace the Methylene Blue method. We use Rhodamine 6G as an extractive reagent and 4-methyl-2-pentanone as an extraction solvent. This method is based on an ion pair extraction process, i.e., BF4- and 10 µM Rhodamine 6G form an ion-pair in the water phase and the ion-pair is extracted into 4-methyl-2-pentanone. The absorbance of the organic phase was measured with a spectrophotometer at 530 nm. The calibration curve was linear up to 7 µM of boron. The method could be applied to the determination of boron in the steel standard sample (JSS-174-7).
Keywords : Methylene Blue; Rhodamine 6G; ion pair extractive method; 1,2-dichloroethane; 4-methyl-2-pentanone.
Norihito Sekishita and Yuko Hasegawa*
*Department of Chemistry, Faculty of Science, Science University of Tokyo, Shinjuku-ku, Tokyo 162-8601
(Received 2 May 2002, Accepted 8 July 2002)Europium(III) was extracted into chloroform with pivaloyltrifluoroacetone (1,1,1-trifluoro-5,5-dimethyl-2,4 hexanedion, PTA) and 2,2'-bipyridyl (2,2'-bpy) or with PTA and 4,4'-bipyridyl (4,4'-bpy). By combining the extractants, the extraction was improved, although the enhancement with PTA and 2,2'-bpy was much larger than that with PTA and 4,4'-bpy (the distribution ratio in the presence of 10-2 M 2,2'-bpy was enhanced by a factor of almost 104, while that in the presence of 10-2 M 4,4'-bpy was as high as 10 times, compared to the distribution ratio in the extraction with PTA, itself, reflecting the function of the bidentate (2,2'-bpy) and the monodentate (4,4'-bpy). In addition, the extracted species with PTA and 4,4'-bpy were accompanied by four PTA and one 4,4'-bpy, EuA3·HA·B as well as EuA3, EuA3·B and EuA3·2B. As the extracted species of lanthanoids(III) with β-diketone and a monodentate Lewis base, such as tributylphosphate, EuA3, EuA3·B and EuA3·2B were reported before. The extraction as EuA3·HA·B may reflect that the Lewis basicity of 4,4'-bpy is similar to that of PTA.
Keywords : synergistic extraction; 2,2'-bipyridyl; 4,4'-bipyridyl; europium(III) chelate; isomer effect.
Yasufumi Takatori, Norio Teshima and Tadao Sakai*
*Department of Applied Chemistry, Aichi Institute of Technology, 1247, Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392
(Received 23 April 2002, Accepted 9 July 2002)Nonionic surfactants, such as TritonX-100 and Brij-35, form cationic compounds in the presence of monovalent metal ions, which associate with an anionic tetrabromophenolphthalein ethyl ester dye (TBPE) to produce an extractable blue ion associate. When tetrakis(4-fluorophenyl)borate (BF4) is added to an aqueous phase, BF4 forms a colorless ion associate with cationic compounds, and the associate is rapidly extracted into 1,2-dichloroethane. At the end point, BF4 takes the cationic compound from the blue ion associate. As a result, a blue color in the organic phase turns out to be yellow because TBPEH is produced. In this work, the addition of 5 ml of 4 M KCl gave a clear end point and RSD with KCl was 0.2%. 1,2-Dichloroethane was suitable in the titration system. Since the ion association formation is stoichiometric, nonionic surfactants can be determined simply and conveniently.
Keywords : nonionic surfactants; ion association reaction; tetrakis(4-fluorophenyl)borate; titration.
Hiroki Saitoh and Keiji Gamoh*
*Faculty of Education, Kochi University, 2-5-1, Akebono-cho, Kochi 780-8520
(Received 24 April 2002, Accepted 20 July 2002)In chromatographic analysis, a suitable derivatization of the bifunctional groups has sometimes been used to enhance the sensitivity and selectivity for detection. Transforming 1,2-diol compounds to the corresponding cyclic boronate derivatives has been more extensively used as a suitable derivatization method for chromatographic and chromatography/mass spectrometric detection. Liquid chromatography/mass spectrometry (LC/MS) with electro spray ionization has been successfully applied to the analysis of diol compounds, pinacol, 2-methyl-2,4-pentanediol, 2,4-dimethyl-2,4-pentanediol, (+)-pinanediol, bicyclohexyl-1,1'-diol, ryanodine and rifampicin, as their m-aminophenylboronate derivatives. Of the range of analytical conditions that were tested, the optimum results were obtained by using reversed-phase LC with a mixture of acetonitrile and 5% acetic acid. The positive-ion spectra of m-aminophenylboronates of the diol compounds showed pseudo-molecular ions, [M+H]+. The [M+H]+ ion was the most abundant for most of the diol compounds, and the [M+H+C5H5N]+ ion was the most abundant for ryanodine. Full-scan mass spectra were readily obtained from 2.6 ng of 2,4-dimethyl-2,4-pentanediol boronate, while a detection limit of 66 fg (signal-to-noise ratio 4) was attained in the selected-ion monitoring mode. This shows that the boronate derivatization of low molecule diols, like pinacol, pinanediol, and so on, contribute to the enhancement of LC/MS detection compared with the direct detection of free diol. On the other hand, in the case of more polar diol compounds, like ryanodine and rifampicine, their boronate derivatization decreased the ionization efficiency upon electrospray ionization.
Keywords : LC/MS; boronate derivative; m-aminophenylboronic acid; diol compounds; ryanodine, rifampicin.
Tomomi Eguchi and Takashi Tomiyasu*
*Department of Earth and Environmental Sciences, Faculty of Science, Kagoshima University, 1-21-35, Korimoto, Kagoshima 890-0065
(Received 4 April 2002, Accepted 24 June 2002)Two procedures were used for the speciation of mercury in marine sediment. One procedure had been proposed for the differential determination of organic mercury, mercury(II) oxide and mercury(II) sulfide in sediments, based on their successive extraction, followed by a cold-vapor atomic absorption spectrometric determination. In this method, organic mercury was first extracted by shaking a sediment sample with chloroform. Another procedure had been proposed for the differential determination of inorganic and organic mercury in environmental and biological materials. In the latter procedure, mercury was first extracted by shaking a sample with 1 M hydrochloric acid containing 3% sodium chloride in the presence of copper(I) chloride. In order to separate organic mercury from inorganic mercury, the extract was shaken with chloroform to extract only organic mercury. In the current investigation, they were suggested that not only methylmercury, but also mercury bound with organic matter in the sediment, could be determined as organic mercury by the former procedure, and that the organic mercury determined by the latter procedure corresponded to methylmercury. These procedures were applied to the speciation of mercury in sediments from Minamata Bay and Kagoshima Bay. In sediments taken in the vicinity of submarine fumaroles in Kagoshima Bay, 7~37% of the total mercury existed as organic mercury, which was considerably higher than 1~4% in the Minamata Bay sediment.
Keywords : speciation; mercury bound with organic matter; fractional extraction; cold-vapor AAS; sediment.
Mizue Takahashi, Masahiro Takahashi and Kazuo Miyamura*
*Department of Chemistry, Faculty of Science, Science University of Tokyo, 1-3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601
(Received 30 April 2002, Accepted 24 July 2002)The tunnel-current to tunnel-gap-width dependences, i.e. the I-s characteristics, of electrochemically prepared STM tips and those of mechanically prepared tips were measured and compared. The I-s characteristics of the electrochemically prepared tips were moderately uniform, which indicates that the sharpness of the tip was uniform. However, the slopes of the I-s characteristics still varied greatly with the tip. The degree of the variety is presented.
Keywords : scanning tunnelling microscope; I-s characteristics; electrochemical etching; tip.
Go to the page of "Bunseki
Kagaku"
Go to the top page of JSAC©2002 The Japan Society for Analytical Chemistry
All rights reserved.
26-2, Nishigotanda 1-chome, Shinagawa-ku, Tokyo 141-0031, JAPAN