Vol. 4 8, No. 9
September, 1999
Fumio Mizutani
National Institute of Bioscience and Human-Technology, 1-1, Higashi, Tsukuba-shi, Ibaraki 305-8566
(Received 30 April 1999)Biosensors combining the specificity of enzymatic reactions with electrochemical signal transduction have attracted increased interest in the last decades. Particular efforts in this field have recently been directed to the development of simple, rapid and reproducible procedures for constructing biosensors. Techniques for preparing chemically modified electrodes (CMEs) are useful for this purpose. This review focuses upon the preparation of biosensors of the CME-type, and emphasized innovative biosensor designs for exhibiting such high-performance characteristics as rapid response and high sensitivity.
Keywords : enzyme-based biosensors; chemically-modified electrodes; amperometric measurements; enzyme immobilization; elimination of interferents.
Toshio Shigematsu*, Koji Shikano* and Hiroki Yonezawa**
*Photonics Laboratories, Nippon Telegraph and Telephone Corporation, Tokai, Ibaraki 319-1193
**Access Network Service Systems Laboratories, Nippon Telegraph and Telephone Corporation, 1-7-1, Hanabatake, Tsukuba-shi, Ibaraki 305-0805
First, instrumental methods were studied to develop the charged particle activation analysis of oxygen, nitrogen, carbon and boron in purified iron. Carbon and nitrogen could be determined instrumentally by bombardment with lower than 4 MeV deuterons and 5.5 MeV protons so as to avoid interference of the radionuclides induced from the iron matrix. Chemical separations containing substoichiometric precipitation were developed for oxygen and boron at the 0.1 ppm level. These analytical methods were applied to the same iron purified for oxygen analysis. The accuracy of such standardization methods as the numerical integration and the average cross section, and the influence of co-existing elements, such as sodium, are also discussed.
Keywords : substoichiometric analysis; oxygen; nitrogen; carbon; boron; charged particle activation analysis; high-purity iron.
Atsushi Furusaki
Asahikawa National College of Technology, 2-2, Syunkodai, Asahikawa-shi, Hokkaido 071-8142
(Received 28 April 1999, Accepted 8 June 1999)The mass balance of heavy metals (iron, copper, zinc and cadmium) contained in the mid-gut gland (MGG) of scallops in the incineration process was studied. The metal contents in bottom ash, deposited on the tube wall, fly ash, and absorption solutions were measured by atomic absorption spectroscopy (AAS). Although wet MGG contained about an average of 20 ppm cadmium, about 57 % was vaporized when heated at 900°C in air. Most of the vaporized cadmium was deposited on the tube wall, and a certain amount of it was detected from fly ash. When MGG was heated in nitrogen, the remaining cadmium ratio was around 10 %, and cadmium of about 83 % was detected from the tube wall, 6 % from the fly ash, and 1.8 % from the absorption solutions. In the case of heating cadmium metal, only oxidation proceeded in the air atmosphere, while cadmium vaporized nearly 100 % in the nitrogen. It was thus considered that the vaporization of cadmium found during the incineration of MGG was caused by a partial insufficiency of oxygen was generated when the organic mass was burned.
Keywords : scallops; mid-gut gland; incineration; heavy metal; mass balance.
Masamitsu Fukuda, Kazutoshi Shimura and Minoru Takeya
Materials Characterization Center, Central Research Institute, Mitsubishi Materials Corp., 1-297, Kitabukuro-cho, Omiya-shi, Saitama 330-8508
(Received 26 March 1999, Accepted 24 June 1999)High-purity ruthenium metal is only slightly soluble in almost all acidic regents. In this study, we developed decomposition techniques to dissolve Ru metal. We applied a Ru-Ga compound method for the analysis of sodium and potassium because of this compounds form at temperature lower than the boiling points of alkali-metal elements. The Ru-Ga compound was formed by 600°C in the atmosphere, and was decomposed using a HCl-HNO3 solution. The Ru matrix in the sample solution was removed as RuO4 by a H2SO4-HClO4 mixed solution at 350°C. The Ga matrix coexisted in the final solution, though any coexistent Ga was not influenced during measurement of sodium and potassium. All other impurities were determined using the Ru-Sn alloy method. The Ru-Sn alloy was formed at 1400°C in nitrogen gas; it could be dissolved and expelled with a HCl-HNO3 and H2SO4-HClO4-HBr mixture. Appropriate methods, including FE, GF-AAS and ICP-MS, were applied for the determination of Na, K, Fe, Al, Mn, Ni, Cu, Ag, Th and U. The detection limits obtained by these methods were from 0.3 µg g-1 to 0.02 ng g-1.
Keywords : high-purity ruthenium; trace impurities; decomposition technique; Ru-Sn alloy; Ru-Ga compound.
Motoshi Nakamura, Hiroshi Taniguchi, Shinkichi Yamada and Takushi Itou
Faculty of Engineering, Shizuoka University, 3-5-1, Johoku, Hamamatsu-shi, Shizuoka 432-8561
(Received 25 May 1999, Accepted 29 June 1999)Carbaryl and its main metabolite, 1-naphthol, were determined simultaneously using a synchronous second-derivative fluorimetric method. The presence of cetyltrimethylammonium bromide resulted in a four-fold increase in the fluorescence intensity of 1-naphthol together with a large bathochromic shift of the emission spectrum, ca. 100 nm. The synchronous second-derivative spectra of carbaryl and 1-naphthol in the mixture in the presence of CTAB were completely separated by changing the synchronous wavelength interval; with 63 nm the second-derivative spectra of carbaryl were recorded, while with 163 nm those of 1-naphthol appeared. The intensities in the spectra were proportional to the concentration of carbaryl and 1-naphthol. The calibration graphs were linear up to at least 1×10-6 M, and both the correlation factors and detection limits were 0.997, 2.61×10-8 M for carbaryl and 0.999, 2.87×10-8 M for 1-naphthol. Carbaryl and 1-naphthol were completely recovered with a Sep Pak Plus C18 cartridge from some environmental water samples with an adjusted pH of below 6.5, and were successfully determined by the proposed method.
Keywords : carbaryl; 1-naphthol; synchronous second-derivative fluorimetry; solid-phase extraction; surfactant; environmental water.Shigeru Terashima and Masahiro Taniguchi
Geological Survey of Japan, 1-1-3, Higashi, Tsukuba-shi, Ibaraki 305-8567
(Received 7 April 1999, Accepted 28 May 1999)A five-step sequential chemical-extraction scheme is described for the analysis of Au in geological reference samples by solvent extraction/graphite furnace AAS. Each chemical fraction is operationally defined as follows: 1) 0.1 M ammonium chloride for the fraction of exchangeable form; 2) 0.1 M HCl-0.1 M KI for the fraction of amorphous form; 3) 0.1 M HCl-0.2 M KI at about 100°C for the fraction of metal form; 4) a mixture of HNO3 and HCl for the fraction of aqua regia soluble form; and 5) a mixture of HNO3, HCl and HF for the fraction of residual form. The relative standard deviations for Au at levels of 0.6 and 50 ng, with a few exceptions, were 33 and 6 %, respectively. The detection limit was approximately 0.2 ppb for a 0.5 g sample. Satisfactory agreement was observed between the sum of the Au values from exchangeable to residual fractions and the reported total Au values. The analytical results of Au for 11 geological reference samples, such as igneous rocks, sediments, soils and ores were tabulated, and the geological and mineralogical features are discussed.
Keywords : fractionation of Au; sequential extraction/graphite furnace AAS; geological reference samples.
Hitoshi Yamaguchi*, Shinji Itoh*, Shukuro Igarashi**, Kunishige Naitoh** and Ryosuke Hasegawa*
*National Research Institute for Metals, 1-2-1, Sengen, Tsukuba-shi, Ibaraki 305-0047
**Department of Materials Science, Faculty of Engineering, Ibaraki University, 4-12-1, Nakanarusawa, Hitachi-shi, Ibaraki 316-8511
A preparation method of a solution sample in fluorescent X-ray spectroscopy has been developed. There is a considerable constraint in the drying and dropping process in the conventional method using a specially designed filter paper. In the present method for fixing filter paper on a sample holder, no problems, such as distortion or breaking of the filter paper, was caused when a sample solution was heated for drying. By reducing the thickness of the filter paper, the absorption of fluorescent X-rays could be suppressed for light elements. For heavy elements, it was possible to increase the quantity of the dropping sample by increasing the thickness and area of the filter paper. In addition, by using a separating filter paper or a functional filter paper, such as ion-exchange filter-paper, it is possible to collect only the specified element. A performance enhancement of the analytical system and on extension of the fields of application can be expected.
Keywords : microdroplet; X-ray fluorescence analysis; filter-paper; solution samples.
Theingi Kyaw
Department of Chemistry, University of Magway, Yangon, Myanmar
(Awarded by Hiroshima University dated March 25, 1999)The chemiluminescence (CL) reactions of luminol with complexes of bis(acetylacetonato)oxovanadium(IV) and tris(8-quinolinolato)iron(III) in a reversed micellar medium of cetyltrimethylammonium chloride (CTAC) have been investigated in order to develop a flow CL method for vanadium(IV) and iron(III) determinations based on the coupling of solvent extraction with reversed micellar-mediated CL detection. First, an enhancement of the CL emission was observed upon mixing the VO(acac)2 complex in chloroform with the CTAC reversed micellar solution of luminol, even when hydrogen peroxide was absent. The free VO(IV) ion produced transiently from decomposition of the complex at the reversed micellar interface is considered to catalyze the CL oxidation of luminol by dissolved oxygen. Secondly, the CL detection based on the luminol-hydrogen peroxide CL emission, enhanced by the Fe(oxine)3 complex in reverse micelles, was combined with on-line extraction through the formation of the complex, followed by separation through a microporous Teflon membrane. In a sample solution containing Fe(II) and Fe(III), the addition of a reaction process using hydrogen peroxide to oxidize Fe(II) to Fe(III) prior to the extraction in this flow system provides for the determination of total iron, Fe(II) + Fe(III), while only Fe(III) can be determined by the absence of hydrogen peroxide.
(Received May 10, 1999)Keywords : solvent extraction; chemiluminescence; luminol; reversed micellar medium; cetyltrimethylammonium chloride; bis(acetylacetonato)oxovanadium(IV); tris(8-quinolinolato)iron(III).
Toshiro Watanabe
Yaegaki Technology Development Laboratories, Yaegaki Bio-industry Inc., 681, Hayashida, Himeji-shi, Hyogo 679-4298
(Awarded by Himeji Institute of Technology dated March 25, 1999)In this thesis, the author reports on newly developed application techniques of capillary electrophoresis (CE) for food analysis. CE was found to be a useful technique for analyzing natural pigments for food, and simple separation methods have been developed for the simultaneous analysis of individual chemical constituents from three commercial drinks by micellar electrokinetic chromatography (MEKC). Most of these studies are first applications of CE to the analysis of food-color additives and individual constituents in drinks. The author conducted simultaneous measurements of α-amylase and glucoamylase activities in sake rice koji by several CE modes. These methods are new applications of CE for enzyme activity assays, and can be applied to the routine quality control of α-amylase and glucoamylase activities in sake rice koji. The author studied for the analysis of antimutagenic pigment-mediated decomposition of mutagenic Trp-P-2(NHOH) by the in-capillary reaction MEKC. This method, in which the interaction between the Trp-P-2(NHOH) and a pigment, xanthomonasin A, occurs during the electrophoresis and these two compounds are separated and quantitated after the interaction. The in-capillary reaction MEKC method is expected to be widely applicable to the analysis of antimutagenesis. CE will become one of the standard techniques in food analysis in the near future.
(Received May 12, 1999)Keywords : capillary electrophoresis; micellar electrokinetic chromatography; food color additives; α-amylase; glucoamylase; in-capillary reaction MEKC; antimutagenicity.
Rong Wei
Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603
(Awarded by Nagoya University dated March 25, 1999)Lake Baikal, the oldest and deepest freshwater lake in the world, holds 5000~10000 m depth of sediments, corresponding to a record of a 20~30 Ma (million years) period. In the present study, paleo-environmental changes of the Eurasian continent during the past 5 Ma were investigated by performing a multielement determination of the major-to-ultratrace elements in the sediment core samples from Lake Baikal by ICP-AES and ICP-MS. As a result, the vertical profiles of 43 elements in two cores, BDP 93-2 and 96-1, were obtained in concentration ranges from % to sub-µg g-1, and the following paleo-environmental changes were elucidated: (1) The profiles of the Na (Mg, Ca)/AI ratios suggest that a transition of atmospheric cycling triggered by rapid upheaval of the Himalayas occurred about 2.5~3 Ma ago. (2) A spectral analysis of the elemental records shows the Milankovitch cycles, the dominant mechanisms for the periodical climatic changes during the past 1 Ma. (3) The concentration profile of Si shows a quite good correlation with oxygen isotope records (δ18O) of deep-sea sediments, which are indices of the temperature changes of the seawater/earth. Furthermore, a preliminary study on sedimentation processes was carried out by an elemental speciation analysis of the sediments.
(Received May 21, 1999)Keywords : multielement profiling analysis; Lake Baikal; sediment core samples; paleo-environmental changes.
Takashi Ito
Department of Chemistry, Science University of Tokyo, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601
(Awarded by the University of Tokyo dated March 30, 1998)Chemical modification of tips for scanning tunneling microscopy (STM) and atomic force microscopy (AFM) was performed for the selective recognition of surface chemical species on the basis of chemical interactions. Observations of alkanol and alkanoic acid monolayers on HOPG with tips modified with thiol self-assembled monolayers (SAMs) or polypyrroles gave high-resolution STM images in which aligned hydroxyl and carboxyl residues were represented by easily recognizable elevated bands. These selective contrast enhancements seemed to be due to electronic coupling through hydrogen-bond interactions between tip-modifying molecules and the samples. To our knowledge, this was the first study that showed the selective recognition of functional groups with chemically modified STM tips. In addition, this study showed that tips for chemical force microscopy can be prepared by the in situ conversion of terminal functional groups in siloxane SAMs with long alkyl chains. A coordination interaction force that originated from sandwich-type bridging of mercaptomethyl groups on AFM tip and sample by Ag+ was also observed. These results showed that the chemical modification of STM and AFM tips made it possible to detect specific chemical species on the basis of molecule-molecule interactions.
(Received June 9, 1999)Keywords : scanning tunneling microscopy; self-assembled monolayers; polypyrrole; atomic force microscopy; chemically modified tip; chemical interaction.
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