Vol. 50 No. 4
April, 2001
Kazumitsu Saeki*, Takatoshi Matsumoto**, Kazutoshi Tanabe** and Toshio Amano***
*Toyama Industrial Technology Center, 150, Futagami-machi, Takaoka-shi, Toyama 933-0981
**National Institute of Materials and Chemical Research, 1-1, Higashi, Tsukuba-shi, Ibaraki 305-8565
***Opt Research Inc., 3-1-6, Nihonbashi-Honmachi, Chuo-ku, Tokyo 103-0023
Recycling plastics is indispensable from an environmental perspective. In plastic recycling, it is required not only to discriminate among all types of plastics, but also to discriminate among all grades. For this purpose, a rapid and intact method has been developed for discriminating polyethylene grades by combining a near-infrared reflection spectra measurement and a neural-network analysis. The near-infrared spectra in the 1.1~2.2 µm wavelength region was measured five times for each sample of 6 kinds of high-density polyethylene and 8 kinds of low density-polyethylene; a total of 70 spectra were obtained. Normalized second-derivative spectral data were analyzed by a principal-component analysis, which showed a possibility to discriminate between polyethylene grades. Although only a small number of spectral data were used for training, a leave-one-out test of a neural-network analysis revealed an overall performance of 100% to discriminate high and low-density polyethylene samples. It is possible to discriminate between the grades of other plastics (e.g. polypropylene, polystyrene). This method is found to be useful for recycling plastics efficiently and accurately.
Keywords : polyethylene grade discrimination; neural network; near-infrared spectra.
Yoshitsugu Shinozuka and Kazuhiro Toyoda*
*Graduate School of Environmental Earth Science, Hokkaido University, Kita10, Nishi5, Kita-ku, Sapporo 060-0810
(Received 14 December 2000, Accepted 6 February 2001)We investigated the mass-determination method of As content in soil samples. Both HG (hydride generation)/ICP-AES and HG/AAS combined with the procedure of acid digestion in open vessels are commonly used for As determination in soil and sediment samples, which should shorten the dissolution times. We examined two commercial microwave digestion (MWD) systems to evaluate the possibility for the MWD of soil and sediment samples. They yielded poor results compared to the recommended values from the literature. This is probably because the resistant organic matter found after MWD contains a significant amount of As, and the residual component hinders a complete dissolution of the samples. We also evaluated the usefulness of ENAA (epithermal neutron activation analysis) for sediment reference samples and a large number of lake sediments, and compared the results with HG/ICP-AES for the mass-determination of As contents. The limit value of the determination (10σ) during a routine analysis was about 0.7 ppm in the samples. This is several times higher than that of HG/ICP-AES, but is satisfactory low for the determination of As in almost all soil samples. About 7 days are required for the As determination of 100 sediment samples by routine ENAA, which is equivalent to the time required for HG/ICP-AES. The total amount of actual work of ENAA is significantly less than that of HG/ICP-AES. We thus realized that ENAA should be recommended for the As determination of a number of sediments and soil samples.
Keywords : arsenic; soil sample; microwave digestion; hydride generation/ICP-AES; epithermal neutron activation analysis.
Bunbunoshin Tomiyasu, Takashi Ogura, Hayato Takeuchi*, Masanori Owari** and Yoshimasa Nihei*
*Institute of Industrial Science, The University of Tokyo, 7-22-1, Roppongi, Minato-ku, Tokyo 106-8558
**Environmental Science Center, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033
Information concerning the chemical composition of such light elements as carbon is one of the most important factors for the accurate characterization of environmental aerosol particles: diesel exhaust particles (DEP), tire dust particles, etc. In the conventional energy dispersive X-ray spectrometer (EDS), on general principles, it was impossible to detect the characteristic X-rays of light elements below an atomic number of 10. These characteristic X-rays can be detected by using a recently developed EDS with a polypropylene ultra-thin-layer detection window. In this study, we tried to accurately charactarize DEPs and tire dust particles by using an electron probe microanalysis (EPMA) apparatus equipped with this novel EDS, and developed a novel sampling method for preparation and collection. It was clarified that an EPMA sample holding environmental particles on a gold surface rigidly could be prepared by the developed sampling method for preparation or collection. From scanning electron microscope (SEM) images and the X-ray spectra of individual particle, such as a DEP, accurate information concerning the shape and chemical composition could be given. A clear source apportionment of tire dust particles and minerals of soil particles, whose X-ray spectrum patterns, except for light element information, are similar, was realized with the carbon Kα X-ray intensity as a direct estimation index.
Keywords : diesel exhaust particle; environmental aerosol particles; electron probe microanalysis; light elements; carbon.
Ming Lu*, Toshihiro Horiguchi, Hiroaki Shiraishi, Yasuyuki Shibata**, Mitsuru Abo, Akira Okubo and Sunao Yamazaki*
*Department of Applied Biological Chemistry, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657
**Environmental Chemistry Division, National Institute for Environmental Studies, 16-2, Onogawa, Tsukuba-shi, Ibaraki 305-0053
In order to clarify the effect of the contamination of organotin compounds in a marine environment on the imposex of gastropods, the speciation and levels of steroid hormones of the organisms were investigated by means of the GC/MS method. Testosterone and 17β-estradiol were first identified and quantitated in the testes and ovaries of Thais clavigera, respectively. In addition, androsterone, estrone and ethynylestradiol were also found in the respective tissues of Babylonia japonica. The extraction and refining procedures were constructed, and the passage of C8-SPE was quite effective for clean-up of the steroid fractions. The recovery of testosterone and 17β-estradiol through the whole procedure were examined by adding a surrogate compound, 17β-estradiol-d3. Good recoveries of between 83% and 96% were obtained. Based on these, the concentrations of testosterone in the testes and 17β-estradiol in the ovaries of both marine gastropods were well determined. The testes of Babylonia japonica were stained both histologically and immunohistochemically to observe the presence of inter- stitial cells, testosterone producing cells known in mammals.
Keywords : testosterone; estradiol; GC/MS; Thais clavigera; Babylonia japonica.
Kazuyo Tagusari, Nobuo Uehara and Tokuo Shimizu*
*Department of Applied Chemistry, Faculty of Engineering, Utsunomiya University, 7-1-2, Yoto, Utsunomiya-shi, Tochigi 321-8585
(Received 4 December 2000, Accepted 9 February 2001)Thermo-sensitive copolymers, poly(N-isopropylacryl- amide-co-methacrylhydroxamic acid), were synthesized and studied concerning their characteristic phase transition and collection of metal ions. As the molar feed ratio of hydroxamic acid group in the copolymer increased, the phase-transition temperature (lower critical solution temperature) of the copolymer increased and the phase transition became difficult. The reason was that the introduction of hydroxamic acid group into the copolymer made the copolymer hydrophilic. The copolymers were dissolved in water homogeneously and were able to react with metal ions. It was found that the metal ions could be collected by the copolymer without hydrolysis of the metal ion. Especially, Fe(III) ion was collected entirely in the 5.0~10.0 pH range. It was suggested that hydroxamic acid group in the copolymer did not form higher-order chelates.
Keywords : thermo-sensitive polymer; metal chelate; hydroxamic acid group; polymer-mediated extraction.
Mitsuyoshi Watanabe*
*Materials Research Laboratory, Technical Center, NGK Insulators, Ltd., 2-56, Suda-chou, Mizuho-ku, Nagoya 467-8530
(Received 28 July 2000, Accepted 6 February 2001)Because SiC prepared by chemical vapor deposition(CVD) has a high density, high strength and oxidation resistance, its pulverizing with alumina or tungsten carbide mortar prior to alkali fusion causes severe contamination. On the contrary, the alkali fusion of coarse or crushed SiC is very vigorous, resulting in loss by bumping. A crushed sample of 0.25 g can be fused under a gentle condition with 0.1 g of iron(III) oxide and 3 g of a mixture(6:1) of sodium carbonate and boric acid. Alter a cake was dissolved in hydrochloric acid, the total silicon was determined with agglomerated mass plus inductively coupled plasma atomic emission spectrometry (ICP-AES). Through this method, it was possible to determine with high precision the total silicon content of SiC. The proposed method enables one to determine the relation between the synthetic condition and the composition of the main component.
Keywords : CVD-SiC; total silicon; iron(III) oxide; alkali fusion.
Kazuhiro Yamaguchi, Nobuo Uehara, Ikuto Hiramatsu and Tokuo Shimizu*
*Department of Applied Chemistry, Faculty of Engineering, Utsunomiya University, 7-1-2, Yoto, Utsunomiya-shi, Tochigi 321-8585
(Received 12 December 2000, Accepted 8 February 2001)The determination of trace amounts of cobalt in iron and steel by reversed-phase HPLC was studied. The iron and steel were decomposed with a mixture of hydrochloric acid and nitric acid. After hydrochloric acid was added into the decomposition solution, the iron matrix in the solution was removed by extraction with 10 cm3 of 4-methyl-2-pentanone. The decomposition solution was then fumed by sulfuric acid and dried. The residue was dissolved in 5 cm3 of dilute nitric acid, followed by diluting to an appropriate volume with water. An aliquot of this solution was taken into 10 cm3 of a volumetric flask and 1.0 cm3 of a 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol solution (5×10-3 mol dm-3); then, 1.0 cm3 of tris(hydroxymethyl)aminomrthane buffer (2.0 mol dm-3, pH 8.0) were added. After the solution was diluted to 10 cm3, 100 mm3 was injected into the liquid chromatogph. The eluent used was aqueous-methanol (40:60 w/w) containing 1.25×10-3 mol kg-1 of EDTA, 5.0×10-3 mol kg-1 of tetrabuthyammonium bromide, and 1.0×10-2 mol kg-1 of acetate buffer (pH 4.0). The eluant was monitored at 589 nm. The calibration graphs were linear over the range from 1×10-9 mol dm-3 to 1×10-7 mol dm-3. The detection limit, defined as 3σ {3-times the standard deviation of the blank value(n=5)}, was 4.4×10-10 mol dm-3. Both the standard addition method and the calibration curve method based on the peak heigh were available for the deternimation of cobalt. The HPLC method was applied to iron and steel certified reference materials. The cobalt contents in the CRMs determined by this method agreed with the guaranteed ones.
Keywords : 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol; HPLC; cobalt; steel and iron; certified reference material.
Masayuki Minakawa®* and Mitsuo Uematsu**
*Japan Science and Technology Corporation, 4-1-8, Hon-cho, Kawaguchi-shi, Saitama 332-0012
**Ocean Research Institute, The University of Tokyo, 1-15-1, Minamidai, Nakano-ku, Tokyo 164-8639
A method involving chemical decomposition and analysis using microwave acid digestion and inductively coupled plasma atomic emission spectrometry (ICP-AES) is proposed for the rapid determination of multi-elements in geochemical samples. Samples of less than 0.3 g were placed in a Teflon pressure vessel, to which 3 ml each of HNO3 and HClO4 were added. The vessel was sealed and irradiated under stepwise stages: 1 min at 250 W, 1 min at 0 W, 5 min at 250 W, 5 min at 400 W and 10 min at 650 W. The vessel was cooled for 30 min in a water bath. The vessel was carefully opened and 4 ml of HF was added. Irradiation was repeated once again under another set of stepwise stages: 1 min at 250 W, 1 min at 0 W, 5 min at 250 W, 5 min at 400 W, 10 min at 650 W and 30 min at 500 W. After cooling, the acid solution was evaporated down to several ml using an acid recovery module, and then to dryness in a Teflon dish. The residue was dissolved in 1.25 ml of 12 M HCl and diluted with pure water in a 25 ml Teflon volumetric flask. The entire procedure took less than 6 hours, including 2.5 to 4.0 hours digestion. Thirty elements in soil, aerosols and marine sediment were determined by ICP-AES. The analytical results were in good agreement with reference values for the sample material.
Keywords : microwave; acid digestion; ICP-AES; multi-elements; soil, aerosols and marine sediment.
Hiroyuki Kamiguchi and Sadamitsu Shiode*
*Water Examination Laboratory of Osaka Municipal Waterworks Bureau, 1-3-14, Higashiyodogawa-ku, Osaka 533-0024
(Received 25 September 2000, Accepted 19 January 2001)We applied a solid-phase extraction method to the analysis of nonionic surfactants in environmental water samples by a spectrophotometric determination. The cartridge columns which we studied were an octadecyl-bonded silica(C18) cartridge, a cyano propyl-bonded silica(CN) cartridge, a polystyrene gel(PS-2) and an activated carbon (AC-2) cartridge. Elution was conducted using a 5% methanol-toluene solution. From the results concerning the recovery efficiency of heptaoxyethylene dodecyl ether (standard for analysis of nonionic surfactant, C12EO7) using the above-mentioned cartridges, the C18 cartridge was found to be higher than that of other cartridges. On the other hand, concerning the removal efficiency of contaminants, such as a cationic surfactant and anionic surfactant coexisting in water, the CN cartridge had a higher performance than the other cartridges. Therefore, the solid-phase extraction method, which combined a C18 cartridge with a CN cartridge, was most applicable for the analysis of nonionic surfactants. Also, the recovery percent of C12EO7 from environmental water samples was 97 to 104%.
Keywords : nonionic surfactant; thiocyanate-iron(III); solid-phase extraction.
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