Vol. 4 9, No. 1 0
October, 2000
Shoji Imai*
*Department of Chemistry, Faculty of Integrated Arts and Sciences, The University of Tokushima; Tokushima 770-8502
(Received 26 April 2000)The mechanistic behaviors of chemical reactions are reviewed together with those for the surface structure and chemical species in a graphite furnace for electrothermal atomization atomic absorption spectrometry. The nanostructure of a graphite surface and a kinetic analysis based on heterogeneous kinetics is also discussed along with the formation of individually dispersed atoms and clusters, gaseous chemical species, and the time-spatial inhomogeneities of atoms and molecules in the furnace cavity. A recent advancement concerning analysis of surface structure and chemical species is shown. It is briefly reviewed that these fundamental studies can be applied as a probe of surface interactions, a thermal reactor for ETV techniques, and a new furnace design.
Keywords : graphite furnace; surface structure; kinetics; pyrolysis; atomization; electrothermal atomization; atomic absorption.
Hideo Asakura, Katsushige Ikegami, Yukari Nakai* and Hisanobu Wakita**
*Research Center, Shinagawa Refractories Co., Ltd., 707, Imbe, Bizen-shi, Okayama 705-8577
**Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1, Nanakuma, Jonan-ku, Fukuoka 814-0133
The chemical components in alumina-chrome (AC) refractories were determined by X-ray fluorescence spectrometry (XRF) using glass beads (GB). AC refractories which contain much Cr2O3 can not be fused with only Li2B4O7. Thus, LiNO3 must be added as an oxidizing agent. The fusing conditions for the GB were chosen as follows: sample (0.2000 g)-Li2B4O7 (3.0000 g)- LiNO3 (3.000 g), 1250°C-10 min. Complete fusion of the Cr-containing sample was suspected to have been proceeded by the formation of CrO42-, caused by the oxidation of Cr(III), converting it to Cr(VI). This possibility was investigated by the CrK-edge X-ray absorption near-edge structure (XANES) spectra. According to preliminary results of Cr(VI) by XANES, the Cr(VI) content in a GB prepared with only Li2B4O7 was merely 7% against the total Cr, but in the GB with Li2B4O7 and LiNO3 it was 39%. Moreover, the Cr(VI) content in the GB with Na2B4O7 and NaNO3, which could be easily fused, but could not be used for actual analysis, because of the contain Na2O content, was 95%. The GBs used for the calibration curve were prepared by accuratly weighing alumina system reference materials and reagent Cr2O3 on a micro-balance of 1 µg accuracy limit and fusing them with Li2B4O7 and LiNO3. As a result, the accuracies (SD) of the calibration curves prepared with these GBs were very satisfactory for Al2O3: 0.21 mass%, Cr2O3: 0.07 mass%, SiO2: 0.027 mass% and so on.
Keywords : X-ray fluorescence spectrometry; refractory; alumina-chrome refractories; glass bead; Al2O3; Cr2O3; ash melting furnace.
Tadao Sakai*
*Department of Applied Chemistry, Aichi Institute of Technology, 1247, Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392
(Received 27 April 2000, Accepted 13 July 2000)Sulphonephthalein dyestuffs, such as Bromophenol Blue (BPB), Bromochlorophenol Blue (BCPB), Tetrabromophenol Blue (TBPB) and Bromocresol Green (BCG), react with quaternary ammonium salts (R4N+) to form 1:2 blue ion associates. However, its extractability and the linearity of the calibration graph are not good. When cinchona-alkaloids, quinine, quinidine, cinchonine and cinchonidine coexist in the sulphonephthalein dyestuff-R4N+ extraction system, a new ion associate (a ternary ion associate) is formed, and the extractability is enhanced. The dynamic range is enlarged compared with that of the blue dyestuff-R4N+ associate. Ternary ion-associate formation by the addition of a cinchona-alkaloid is useful for the determination of trace amounts of quaternary ammonium salts and cationic surfactants.
Keywords : formation of ternary ion associate; diprotic sulphonephthalein dyestuffs; cinchona-alkaloids; trace analysis of quaternary ammonium ions.
Yoshiaki Ishii, Satoshi Okita, Makoto Torigai and Sun-Ja Yun*
*The Institute of Basic Environmental Research, Environmental Control Center Co., Ltd., 323-1, Shimoongata-machi, Hachioji-shi, Tokyo 192-0154
(Received 9 June 2000, Accepted 27 July 2000)An analytical method for the simultaneous determination of estrogens (17beta-estradiol, 17alpha-estradiol, estrone, ethinylestradiol) by liquid chromatography/tandem mass spectrometry (LC/MS/MS), following sample pretreatment by solid-phase extraction using a C18 cartridge, back extraction from the water phase with ethyl acetate and cleaned up using NH2 cartridge, has been developed. It has been observed that the main fragment negative ions with electrosplay ionization (ESI) were deprotonated molecules, [M-H]-, for each compound, as follows: 17beta-estradiol and 17alpha-estradiol, m/z 271; estrone, m/z 269; ethinylestradiol, m/z 295. The product ion, m/z 145, was obtained from all compounds using a collision energy of 50 eV. The detection limits of four compounds ranged from 0.1 ng/ml to 0.5 ng/ml. Good linearity (r≥0.998) of the calibration curve was obtained in the concentration range from 0.5 ng/ml to 100 ng/ml for all compounds. The present method has been successfully applied to the determination of estrogens in environmental water samples, such as river water and the discharge of sewage treatment plants.
Keywords : LC/MS/MS; 17beta-estradiol; estrogens; river water; discharge of sewage treatment plant.
Zilin Chen, Katsumi Uchiyama and Toshiyuki Hobo*
*Department of Applied Chemistry, Graduate School of Engineering, Tokyo Metropolitan University, 1-1, Minamiosawa, Hachioji-shi, Tokyo 192-0397
(Received 10 May2000, Accepted 1 August 2000)Hydroxy acid enantiomers have specific bioactivity. Much attention has been paid to their analytical separation. This work investigated their separation and behavior by ligand exchange-micellar electrokinetic chromatography using Cu(II)-L-OH-proline complexes as chiral selectors. Previous work showed that D-amino acid enantiomers migrated faster than L-analogues when Cu(II)-L-proline complexes were used as chiral selectors. The enantiomer migration orders (EMO) of amino acids were reversed by introducing the SDS micellar phase. In the case of hydroxy acid enantiomers, however, it was observed that L-enantiomers migrated faster than the D-forms in both cases of without and with the SDS micellar phase. When CTAB was added to running electrolytes, D-enantiomers migrated as the first peak. Further, when the ligands were changed, different EMOs were observed. The resolution condition, mechanism and behaviors are discussed in this paper.
Keywords : hydroxy acid enantiomers; ligand exchange; micellar electrokinetic chromatography; chiral separation.
Fumiaki Yokota, Akiko Shimizu*, Toshio Ishizuka** and Hisashi Morikawa***
*Material Department, Industrial Research Institute, Aichi Prefectural Government, Nishi-Shinwari, Hitotsugi-cho, Kariya-shi, Aichi 448-0003
**Faculty of Science, Niigata University, 8050, Ikarashi 2, Niigata 950-2181
***Chemistry Department, National Industrial Research Institute of Nagoya, 1-1, Hirate-cho, Kita-ku, Nagoya 462-8510
In order to determine impurities (thirteen elements) in niobium carbide (NbC) by inductively coupled plasma atomic emission spectrometry (ICP-AES), a sample dissolution procedure using acids was examined. A 0.25 g amount of NbC powder sample was taken in a Teflon pressure vessel, and 2 ml of hydrofluoric acid (1+1) and 10 ml of nitric acid (1+9) were added. The vessel was sealed and kept at 160°C for 16 hours in a drying oven. After cooling, the mixture was filtrated so as to remove any small amount of insoluble free carbon which existed in the sample. The filtrate was transferred to a 100 ml calibrated flask, and diluted with distilled water to volume. Thirteen elements (Al, Ca, Co, Cr, Fe, Mg, Mn, Ni, Ti, Ta, V, W and Zr) were determined by ICP-AES. The matrix effects of Nb on the background levels and the emission intensities of the elements of interest were compensated by using matrix-matched standard solutions for the calibration. Thirteen elements in commercial NbC powder samples were determined with good precision. The recoveries of thirteen spiked elements were 95% for Ni to 103% for Co, Fe and Mn; the detection limits were 0.04 µg g-1 for Mg to 11 µg g-1 for Al.
Keywords : ICP-AES; impurity determination; niobium carbide; advanced ceramic; acid decomposition under pressure.
Mitsuyoshi Watanabe and Akira Narukawa*
*Materials Research Laboratory, Corporate R&D Group, NGK Insulators, Ltd., 2-56, Suda-cho, Mizuho-ku, Nagoya 467-8530
(Received 14 April 2000, Accepted 29 July 2000)Silicon nitride has been widely used for the engine parts of cars and as mechanical parts due to its thermal stability and corrosion resistance. The oxygen contained in raw materials significantly influences the sintering property. Nitrogen determination is also important as one of the main components. The oxygen and nitrogen in silicon nitrides are measured by the infrared absorption of carbon monoxide and the thermal conductivity of nitrogen after inert-gas fusion. Prior to fusion, a sample was taken in a small Ni capsule and easily molded in only 30s by a newly designed automatic press machine. The capsule was melted with tin metal in a fusion apparatus. The accuracy and reproducibility of both elements in raw powder and sintered silicon nitrides were similar to or better than those by conventional manual molding.
Keywords : automatic molding of Ni capsule; oxygen; nitrogen; silicon nitride.
Yuki Nakada, Mari Sakai, Masafumi Hinata and Teruo Suzuki*
*Consumer Protection Department, National Institute of Technology and Evaluation, M. I. T. I., 2-49-10, Nishihara, Shibuya-ku, Tokyo 151-0066
(Received 6 April 2000, Accepted 3 August 2000)Plastic containers for food must be made in accordance with the Food Sanitation Laws,and there are migration standards for particular components. However, there no standards have been set for the styrene monomer, dimers and trimers. The dimers and trimers have been selected as potential environmental endocrine disrupters by the Environment Agency. We investigated the actual migration amounts of the styrene monomer,dimers (4 substances) and trimers (5 substances) for several solvents on commonly used food containers, such as commercial instant-noodle containers (6 samples), disposable plastic cups (5 samples) and convenience-store lunch containers (2 samples). The experimental results were as follows: with n-heptane, the dimers were found at concentrations of 15.6~745 ppb and the trimers at 208~6110 ppb; when the solvent was 20% ethanol,the styrene monomer was measured at 0.11~1.5 ppb, the dimers at concentrations of 0.353~4.86 ppb, and the trimers at 0.892~9.87 ppb; and when the solvent was water, the styrene monomer was 0.14~2.6 ppb, the dimers were 0.035~1.291 ppb, and the trimers were N.D.~2.666 ppb. We also investigated the total amounts of the dimers and trimers included in the plastic containers. The dimers and trimers were measured at levels from 171 to 426 ppm and from 3260 to 12800 ppm, respectively.
Keywords : styrene monomer; styrene dimers; styrene trimers; migration test; material test; GC/MS
Kunihiro Watanabe, Yoshiteru Minowa and Masayuki Itagaki*
*Faculty of Science and Technology, Science University of Tokyo, 2641, Yamazaki, Noda-shi, Chiba 278-8510
(Received 5 April 2000, Accepted 1 July 2000)A catalytic analysis based on a decomposition reaction of azo compounds is a highly sensitive determination method of Co(II). In the system which makes an azo compound to be an indicator reagent, metal complex formation with the azo compound is necessary for metal ions to be a catalyst. The arsenazo III used in this study as an indicator reagent is known to be a colorimetry reagent of rare earths. However, the formation of a complex with Co(II) was not known. It was found that Co(II) formed the complex in a strong alkaline medium and that it accelerated the color-fading reactions of arsenazo III. Then, a catalytic analysis method of Co(II) by arsenazo III in a strong alkaline medium was examined. A calibration curve was made between ln(A1/A10) and the concentration of cobalt(II), where A1 and A10 were the absorbance of arsenazo III solution at 1 min and 10 min, respectively. The values of ln(A1/A10) were nearly proportional up to 20 ppb of cobalt (under the optimum conditions: pH 13.7, 1.9×10-5 M arsenazo III, 1.0% H2O2 and 45°C). The detection limit was 0.5 ppb. This method was applied to the determination of cobalt in silica gel without requiring any complicated pretreatment.
Keywords : catalytic method; cobalt determination; cobalt-arsenazo III complex; strong alkaline medium.
Shigeru Terashima*
*Geological Survey of Japan, 1-1-3, Higashi, Tsukuba-shi, Ibaraki 305-8567
(Received 13 April 2000, Accepted 24 July 2000)A simple and sensitive method for the determination of In and Te in geological reference materials is presented. A sample of 0.01 to 1.0 g, containing less than 50 µg of Bi, Pb, or Sn, and 100 µg of Cu, was decomposed with aqua regia and HF. The contents were then evaporated to dryness. The residue was dissolved by heating with diluted HCl, and centrifuged to remove any undissolved material. After the addition of sulphamic acid, potassium iodide-ascorbic acid, and palladium solutions to the supernatant, In and Te were extracted into 0.5~1.0 ml of MIBK containing 5% trioctylmethylammonium chloride, and determined by graphite-furnace AAS. Although interference from most elements could be minimized by the addition of palladium as a matrix modifier, a large amount of Bi, Pb, Sn and Cu suppressed the In and/or Te absorbance. The relative standard deviation was smaller than 10% for a content larger than 3 ng of In and Te, and the limit of detection for both elements was 0.2 ng/g for a 1 g sample. This method was successfully applied to the determination of In and Te in various geological reference materials.
Keywords : indium; tellurium; organic solvent extraction; graphite-furnace AAS; geological reference materials.
Nobutaka Yoshikuni, Seiichi Nishiumi and Koichi Oguma*
*Department of Materials Technology, Faculty of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522
(Received 10 May 2000, Accepted 28 July 2000)The preparation and application of a coated-graphite tellurium(IV) ion-selective electrode, based on the TeCl62- form anion-exchange resin fixed in a poly(vinyl chloride) matrix, are described. The effects of the hydrochloric acid concentration and interference ions were investigated. The electrode showed a near-Nernstian slope of 30±2 mV/decade over a tellurium(IV) ion concentration range of 3×10-4-10-2 mol dm-3 and a response time of 30 s in 6 mol dm-3 hydrochloric acid solution. Na+, K+ and Ca2+ do not interfere, but other ions, such as Bi3+, Cd2+, Fe3+, Ga3+, Sb3+,ClO4-, PO43- and SO42-, cause interference. The electrode has been successfully used to determine tellurium in Bi2Te3 and CdTe after the separation of tellurium from bismuth or cadmium by the hydroxide precipitation method in the presence of EDTA as a masking reagent for bismuth and cadmium.
Keywords : tellurium; ion selective electrode; anion-exchange resin; bismuth telluride; cadmium telluride.
Kunikazu Ide, Koichi Sato* and Shinya Hashimoto**
*National Research Institute for Metals, 1-2-1, Sengen, Tsukuba-shi, Ibaraki 305-0047
**Tokyo University of Fisheries, 4-5-7, Kounan, Minato-ku, Tokyo 108-8477
An accurate and sensitive analytical method for total tin in shellfish samples has been established. Graphite-furnace atomic absorption with a highly efficient atomization method was examined. Good results were obtained by applying a matrix modifier of nickel addition, high-speed temperature rising of the graphite tube, an area-integral measurement and an AC Zeeman-effect background correction. The direct analysis of a sample solution and high sensitivity were achieved by this method. Blue mussel samples collected from Tokyo Bay (Daikoku and Ukishima) and the coast of Kujukuri were analyzed. Homogenized samples were freeze-dried. After nitric acid (10 ml), hydrofluoric acid (5 ml) and perchloric acid (5 ml) were added to a dried sample (0.5 g), it was decomposed by heating. The sample solution was vaporized to dryness and the residues was dissolved with nitric acid (3 ml) . The sample solution (20 µl) and a nickel solution (20 g l-1; 5 µl) were injected onto a platform in a graphite tube and measured by graphite-furnace atomic-absorption spectrometry. The total tin concentration of mussel was 0.5 ppm (Daikoku), 0.8 ppm (Ukishima), and <0.1 ppm (Kujyukuri). A certified reference material (NIES No.11) was analyzed, and a good result was obtained.
Keywords : total tin in shellfish; graphite furnace atomic absorption spectrometry; nickel as matrix modifier; blue mussel samples; STPF technique; AC zeeman effect background correction.
Hiroshi Kawaguchi
Mitsui Mining & Smelting Co., Ltd., Corporate R&D Center, 1333-2, Haraichi, Ageo-shi, Saitama 362-0021
(Awarded by Utsunomiya University dated March 24, 2000)The need for highly sensitive and reliable methods for the determination of ultratrace elements has been recognized in analytical chemistry and/or environmental science. The author has developed micro-volume back-extraction methods for the ultratrace analysis of gallium, indium and thallium. At first, the determination of gallium and indium at ng dm-3 levels in natural water samples was investigated. Gallium or indium was extracted into carbon tetrachloride as an ion pair of 5-sulfo-8-quinolinol chelate anion with tetradecyldimethylbenzyl-ammonium chloride, and subsequently back-extracted into 0.3 cm3 of nitric acid solution for determination by GFAAS. In the case of indium, the extraction behavior of the ion associate was compared with that of the 8-quinolinolato complex. Secondly, the determination of thallium at ng dm-3 levels in natural water samples was investigated. Thallium is extracted into chloroform as the dithizonate complex, and subsequently back-extracted into 0.3 cm3 of a nitric acid solution. A speciation analysis of Tl(I) and Tl(III) is performed by the masking of Tl(III) with citrate and/or the reduction of Tl(III) to Tl(I) with ascorbic acid. The detection limits obtained for these elements are sub ng dm-3 levels, based on more than 1000-fold preconcentration.
(Received June 21, 2000)Keywords : solvent extraction and back extraction; graphite-furnace AAS; 5-sulfo-8-quinolinol; tetradecyldimethylbenzylammonium chloride; 1,5-diphenylthiocarbazone.
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