Vol. 4 9, No. 5
May, 2000
*Faculty of Systems Engineering, Wakayama University, 930, Sakaedani, Wakayama 640-8510
(Received 17 January 2000)Ion sensors include electrochemical sensors to detect analyte ions electrochemically, i.e., membrane-potential sensors, such as ion-selective electrodes; voltammetric sensors, such as chemically-modified electrodes; and optical sensors to detect them spectrophotometrically, i.e., optodes or optrodes. There has been much information reported so far on ion sensors from two types of research, viz., the development of new sensors and basic studies about the response mechanism of ion sensors. The present review is concernd mainly with research topics of our intered, which include potentiometric anion sensors based on new neutral carriers and metal complexes, biocompatible ion sensors for the continuous detection of analyte ions in biological samples, and optodes for detecting electrically neutral molecules.
Keywords : ion sensors; membrane-potential anion sensors; biocompatible ion sensors; optodes for neutral molecules.
Hideo Asakura, Katsushige Ikegami*, Yasujiro Yamada** and Hisanobu Wakita***
*Research Center, Shinagawa Refractories Co., Ltd., 707, Imbe, Bizen-shi, Okayama 705-8577
**Center for Applied Technology, Rigaku Industrial Corporation, 14-8, Akaoji, Takatsuki-shi, Osaka 569-1146
***Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1, Nanakuma, Jonan-ku, Fukuoka 814-0133
The chemical components in refractories containing silicon carbide were determined by an X-ray fluorescence analysis using glass beads. Good- quality glass beads can be prepared by the following method. After 0.3000 g of a silicon carbide sample is mixed with 3.0000 g of flux (Li2B4O7), the mixture is placed in a Pt-Au alloy dish. It is then fused in a furnace under an O2 atmosphere at 840°C for 33 hours, and finally fused at 1150°C. Since the mass of the resulting glass bead is increased by the oxidation of SiC, which produces SiO2 during sample heating, the ratio of 10:1 between the flux and the sample is changed. For this reason, the popular JIS method of using SiO2-Al2O3 binary calibration curves could not be applied to obtain an accurate analysis with these glass beads. We therefore developed a new calibration method. In this method, the gain on ignition (GOI) is regarded as being a component in the sample, and the theoretical matrix correction coefficients (dj) of each component are calculated by the fundamental parameter procedure (FP procedure) using the GOI as a base component. The GOI-SiO2 binary calibration curves (GOI correction curves) are made with the djs obtained by the FP procedure. With this method the standard deviation (SD) of the GOI correction curves is very satisfactory. Our test results include an SD of 0.24 mass% for SiO2 and 0.096 mass% for Al2O3. The GOI correction curves are applicable to all components in the reference materials, except for Fe2O3.
Keywords : X-ray fluorescence spectrometry; refractory; silicon carbide; glass bead; GOI correction method.
Masaru Mitsushio*, Toshifumi Yoshidome and Satsuo Kamata**
*Department of Applied Chemical Engineering, Graduate School of Engineering, Kagoshima University, 1-21-40, Korimoto, Kagoshima 890-0065
**Department of Applied Chemistry and Chemical Enginnering, Faculty of Engineering, Kagoshima University, 1-21-40, Korimoto, Kagoshima 890-0065
The concentrations of carboxylic acid esters and lubricants were measured by using a gold-coated optical-fiber sensor system. The sensor system consisted of a He-Ne laser, an optical fiber, and a detector. A part of the optical fiber, which was in contact with a sample solution, was coated by a gold thin film after removing the fiber clad. The intensity of the transmitted laser light by the fiber varied with the refractive index of the sample solution. The transmittance of the fiber on ethyl formate with a refractive index below 1.37 decreased with increasing the concentration of the formate, while that of the fiber on the other ester compounds with a refractive index, above 1.37, such as diethyl sebacate and DOS, increased with increasing these material concentrations. The difference in the concentration dependence of the transmittance was thought to be explained on the basis of the refractive index of the sample solution. The sensitivity of this sensor system was good for these carboxylic acid esters and lubricants. In particular, plots of the transmittance against the concentrations of DOS and DOA were liner over the range of 20 to 80%. Thus, this gold-coated optical fiber sensor system can be used to determine the concentration of carboxylic acid esters and lubricants.
Keywords : gold-coated optical-fiber; lubricant; DOS; DOA; carboxylic acid esters.
Akiyo Otsuka, Yasushi Ishihama, Kiyohiko Uchikawa and Naoki Asakawa*
*Tsukuba Research Laboratories, Eisai Co., Ltd., 5-1-3, Tokodai, Tsukuba-shi, Ibaraki 300-2635
(Received 1 February 2000, Accepted 6 March 2000)We developed an N-shaped partition cell to measure the logarithm of partition coefficients between 1-octanol and water (log Pow). The cell enabled us to measure the concentrations of the solute in the two phases periodically by HPLC without any tedious or time-consuming steps. The equilibrium time in the cell was almost 4 hours, and the obtained log Pow values were consistent with those by the conventional shake-flask method for neutral compounds with 1.1 < log Pow < 3.8. This approach was applied to a monovalent basic drug, verapamil, and the dependence of log Pow on the pH was measured using six cells simultaneously. The obtained pKa and log Pow values of verapamil by the N-shaped cell method were in agreement with those by the shake-flask method; the analysis time was alsomst 7 hours. The cell was used in an HPLC autosampler, and the whole operation for measuring log Pow was performed automatically in combination with HPLC.
Keywords : log Pow; octanol-water; N-shaped cell; verapamil.
Shigeru Terashima, Noboru Imai*, Mamoru Tominaga**, Shizuko Hirata*** and Masahiro Taniguchi*
*Geological Survey of Japan, 1-1-3, Higashi, Tsukuba-shi, Ibaraki 305-8567
**National Institute for Resources and Environment, 16-3, Onogawa, Tsukuba-shi, Ibaraki 305-8569
***Chugoku National Industrial Research Institute, 2-2-2, Hirosuehiro, Kure-shi, Hiroshima 737-0197
(Received 1 December 1999, Accepted 9 February 2000)
In order to provide a soil reference material which contains known chemical forms of miner and trace elements, thirty-one reagent materials, mostly in oxides, were artificially added to a natural soil collected from the Kanto loam formation near Geological Survey of Japan(GSJ). The concentrations of added minor and trace elements were about 1000 µg/g for As, Co, Cr, Cu, Mo, Ni, Pb, V, W, Y, Zn, and Zr, 100 µg/g for B, Be, Bi, Br, Cd, Sb, Sn, and Ta, 10 µg/g for Ag, Hg, I, In, Se, Te, and Tl, and 1 µg/g for Au, Pd, Pt, and Rh, respectively. The ingredients were diluted with a small amount of feldspar powder and ground in an agate mortar, then diluted with the same feldspar powder sequentially and ground and mixed in an agate mortar or a small ball mill thoroughly at each dilution step. Finally, a mixture of about 12 kg was diluted with 108 kg of well-dried natural soil using a large ball mill. The sample was screened with a 246 µm (60 mesh) opening of a stainless-steel sieve, and mixed well before packing in glass bottles. A homogeneity test showed that all of the elements studied were homogeneously distributed. Forty-three major, minor and trace elements were determined, and the results were tabulated together with the analytical methods and the outline of sample treatment procedures. Analytical results of the mineral composition by X-ray diffraction are also presented.
Keywords : geochemical reference material; GSJ; JSO-2 soil; minor and trace elements; chemical forms.
Yuichi Kitasako, Tohru Nikaido, Junji Tagami*, Kenichi Ikeda, Kyoko Mitsunari and Satoshi Nomura**
*Cariology of Operative Dentistry, Department of Restorative Sciences Graduate School, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549.
**Horiba Ltd., 2, Kisshoinmiyanohigashimachi, Minami-Ku, Kyoto 601-8510
The aim of this study was to investigate the surface analysis of human teeth using a pH-imaging microscope based on a semiconductor silicon sensor. Disks were cut from freshly extracted non-carious and carious human teeth. Samples were placed on an agar film to evaluate the surface pH distribution. Non-carious samples were treated with 37% phosphoric acid and then thoroughly rinsed. A reduction of the pH value was clearly detected after a phosphoric acid treatment. The pH distribution of carious lesions was lower than that of non-carious lesions. From these results, this pH-imaging technology has the potential to aid in carious assessments and carious treatments.
Keywords : pH-imaging; scanning chemical microscope; human teeth; carious treatments.
Sadao Nakamura, Masahiko Takino* and Shigeki Daishima**
*Kansai branch office, Yokogawa Analytical Systems Inc., 3-3-11, Niitaka, Yodogawa-ku, Osaka 532-0033
**Yokogawa Analytical Systems Inc., 2-11-13, Nakacho, Musashino-shi, Tokyo 180-0006
An analytical method for the determination of potential endocrine disruptors, seven alkylphenols including nonylphenol and 4-t-octylphenol, by gas chromatography/mass spectrometry (GC/MS) with negative-ion chemical-ionization (NICI) has been developed. First, the detection limits by GC/MS-SIM with electron ionization (EI) and NICI were compared for the underivatized and pentafluorobenzyl (PFB) derivatives of alkylphenols. The NICI-SIM of PFB derivatives used an (M-PFB)- ion as the monitoring ion. The reagent gas (methane) flow rate and the ion-source temperature were determined to be 2.5 ml/min and 250°C, respectively, for the optimized NICI-SIM conditions. In the case of EI-SIM, the sensitivities of PFB derivatives were 2.1~6.3 times higher than those of underivatized target chemicals. Furthermore, the sensitivities of PFB derivatives by NICI-SIM were 67~300 times higher than those of underivatized target chemicals by EI-SIM. The detection limits by NICI-SIM ranged from 1.0 pg/ml to 33 pg/ml. This method also provides good linearity of the calibration curve and repeatability. The correlation coefficients of calibration curve were >0.9995 for all chemicals in the concentration range from 1 pg/ml to 10 ng/ml. The relative standard deviations of the peak areas of the target chemicals were 3.6~6.8% for 10 pg/ml, 2.3~4.9% for 100 pg/ml and 2.4~3.5% for 1000 pg/ml. The recoveries of the target chemicals from a river-water sample spiked with standards at 10 pg/ml levels for 4-n-pentylphenol, 4-n-hexylphenol, 4-n-heptylphenol and 4-n-octylphenol, 100 pg/ml levels for 4-t-butylphenol and 4-t-octylphenol and 5000 pg/ml levels for nonylphenol were 77.9~102%. The relative standard deviations were to be from 4.1 to 12%.
Keywords : alkylphenols; GC/MS with negative-ion chemical-ionization; derivatization with pentafluorobenzyl bromide; endocrine disruptors; solid-phase extraction.
Hisomu Nagashima*, Toshimitu Okamoto**, Yoshimi Dewa and Takatoshi Hattori***
*Institute of Science and Technology, Inc., 3-10-2, Kitashinagawa, Shinagawa-ku, Tokyo 140-0001
**Product Development Laboratories, Sankyo Co., Ltd., 1-2-58, Hiromati, Shinagawa-ku, Tokyo 140-8710
***Yanaco Co., Ltd., 1, Yanagiosa-cho, Shimotoba, Fushimi-ku, Kyoto 612-8472
A method for elemental micro-analysis that employs a novel coupled combustion/ion chromatography(IC) apparatus is described in detail. A sample of 1.0~2.5 mg was weighed and ignited instantaneously in quartz combustion tube at 950°C with a carrier gas comprising oxygen and helium (6:4) at a flow rate of 30 ml/min. The combustion products were collected in 50 ml(total volume) of 0.5% hydrogen peroxide/2 mM sodium hydroxide solution, containing a certain amount of phosphate ion as an internal standard (ISD). After a 50 µl aliquot of each sample solution was injected into a suppressed conductivity ion chromatography system, a 1.8 mM sodium carbonate/1.7 mM sodium hydrogen carbonate solution was eluted under the following operating condition: flow rate, 1.5 ml/min; column temperature, 30°C ; scavenger, 15 mM sulfuric acid. The calibration curves obtained from the peak areas of the anions(F-, Cl-, Br- and SO42-) is linear with high correlation coefficients of more than 0.999 and a good relative standard deviation(RSD, %) of 0.2~0.4% for 10 repeated measurements. The simultaneous determination of fluorine, chlorine, bromine and sulfur in organic compounds was achieved by incorporating this combustion/IC technique. The thus-obtained analytical values are in good agreement, within ±0.3% of the theoretical values for the several compounds tested.
Keywords : automatic analysis for halogens and sulfur in organic compounds; coupled combustion/ion chromatography; measurement of fluoride, chloride, bromide and sulfate ions.
Tatsuhiko Tanaka and Toru Sato*
*Faculty of Engineering, Science University of Tokyo, 1-3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601
(Received 21 January 2000, Accepted 24 February 2000)A simple and precise method is described for the determination of arsenic in fluorspar by differential pulse anodic stripping voltammetry without any pretreatment steps using harmful chemicals. Arsenic(V) was reduced to arsenic(III) with potassium iodide. The arsenic(III) in an acidic solution was electrodeposited on a rotating gold-film electrode at -0.45 V vs. SCE for 180 s, and then a stripping voltammogram was recorded by a positive-going scan at a rate of 40 mV s-1 to 0.2 V vs. SCE. The calibration {peak height vs. arsenic(III) concentration} curve was linear over the range (1.3~4.0)×10-7 M arsenic(III) and passed through the origin. The detection limit (3σ) was 1.98×10-8 M. Copper(II), lead(II), and antimony(III) interfered with the arsenic(III) determination severely. The determination of 10.6 µg g-1 of arsenic in fluorspar was achieved with an RSD (n=5) of 3.4% within 3 h. The proposed method is an improvement over the existing JIS method.
Keywords : arsenic; fluorspar; differential pulse anodic stripping voltammetry; gold film electrode.
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