Vol. 47, No. 4
April 1998
Hirohito Naka, Hirohumi Kurayasu*, Li Ma** and Taketoshi Nakahara***
*Sumitomo Metal Technology, Inc., 1-8, Fuso-cho, Amagasaki-shi, Hyogo 660-0891
**Beijing General Research Institute for Non ferrous Metals, No. 2, Xinjiekou Wai St., Beijing, China 100088; Present address: Shimadzu Scientific Instruments & Equipments Center, 5F, INSTEC Commercial Bldg, B-19 Beisanhuanzhong Road, Xicheng District, Beijing, China 100029
***Department of Applied Chemistry , Osaka Prefecture University, 1-1, Gakuen-cho, Sakai-shi, Osaka 599-8531
A method for the determination of trace amounts of sulfur in high-purity iron by isotope dilution ICP-MS with a hydrogen sulfide evolution technique was established. Hydrogen sulfide evolved by the distillation of sample solutions was collected into sampling bags, and then was introduced directly into the ICP mass spectrometer. The effect of the distillation temperature and Ar carrier gas-flow rate on the distillation time was studied. Hydrogen sulfide was evaporated almost completely for about 20 min of distillation when a distillation temperature of 250°C and an Ar carrier gas flow rate of 100 ml min-1 were selected as the optimized distillation conditions. Optimization of the nebulizer gas-flow rate, rf power and sample gas-flow rate was accomplished by studying the effect of these three parameters on the intensity ratio of 34S+ to 32S+ and background intensity of 32S+ and 34S+. The intensity ratios and backgound intensity reached more stable and lower levels respectively, when a nebulizer gas-flow rate of 0.88 l min-1, an rf power of 1350 W and a sample gas-flow rate of 30 ml min-1 were selected as the optimum operating conditions. The proposed method was successfully applied to the determination of trace amounts of sulfur in Japan Iron and Steel Certified Reference Materials and a high-purity iron sample. The RSD of 2.6% was achieved at a sulfur concentration of 2 µg g-1.
Keywords: sulfur determination; high-purity iron; ICP-MS; isotope dilution; hydrogen sulfide evolution; trace analysis.
Teruo Kitamura, Shigemi Tanimoto*, Masaaki Iwatsuki and Shintaro Nishida**
*Research and Development Department, Showa Aluminum Corporation, 6-224, Kaisan-cho, Sakai-shi, Osaka 590-8576
**Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Yamanashi University, 4-3-11, Takeda, Kofu-shi, Yamanashi 400-8511
A method for the determination of trace amounts of corundum(α-Al2O3), α-quartz and other metallic elements as inclusions in aluminium with X-ray diffraction and fluorescence analyses has been developed. An aluminium sample was melted and filtrated through a porous alumina filter (100 µm in pore size). These inclusions were concentrated in a layer on the filter with almost 100% recovery, and collected on a membrane filter after dissolving matrix metallic aluminum with a bromine-methanol solution. The X-ray intensities of the inclusions on the membrane filter could be measured without any significant interference of the coexisting materials, except for light elements in relatively large amounts of inclusions. The regression coefficients between the intensities and amounts of standard specimens were 0.990~0.999 and the reproducibilities were satisfactory. Corundum in the range of 0.07~0.5 ppm and a-quartz in the range of 0.02~0.09 ppm and the other metallic elements, such as Mg, Al, Si, Ti, Mn, Fe and Cu at the ppb level were determined. Spinel and other inclusions could also be determined by this method.
Keywords: inclusions in aluminium; inclusion filtration apparatus; selective dissolution; X-ray diffractometry; X-ray fluorescence analysis.
Keiichiro Hozumi*, Ayako Satoh** and Naoshige Akimoto***
*Kyoto Pharmaceutical University, 5, Misasagi-Nakauchi-cho, Yamashina-ku, Kyoto 607-8414
**Faculty of Pharmaceutical Sciences, Tohoku University, Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8578
***Faculty of Pharmaceutical Sciences, Kyoto University, 46-29, Yoshida-Shimoadachi-cho, Sakyo-ku, Kyoto 606-8304
The microdetermination of sulfur in organic materials is currently being carried out by a tube combustion or a flask-combustion method. However, either way is not fully reliable for the accurate determination of samples at 1 mg or below. Some years ago, a sealed-tube combustion method was proposed for the submilligram determination of organic halogens, featuring the complete decomposition of samples with small volumes of pure oxygen and no contamination or loss of components during the process. An extension of the same technique has therefore been made for the determination of organic sulfur. A weighed sample and a small volume of oxygen are sealed off in a Pyrex glass tube (od., 10 mm; id., 8 mm; l., 18 cm) having a fine-tip end. The sealed tube is heated in a cylindrical furnace at 580°C for 20 min and drawn out for cooling. The tube is held vertically with the tip end down and is pressed to the bottom of a small beaker containing a 3% H2O2 solution. The tip end is then broken and the solution slowly enters into the tube, raising the liquid level by 2~5 cm. While the tube is left standing for 10 min, the sulfur oxides in the gas phase are entirely absorbed in the liquid phase to be sulfate ion. The sulfate ion can be accurately titrated spectrophotometrically at a wavelength of 660 nm with 0.005 mol/l Ba(ClO4)2 standard solution using carboxyarsenazo as an indicator. Thirty or more determinations per day are feasible if several sealed tubes in one lot are heated in the furnace.
Keywords: microdetermination of organic sulfur; sealed tube combustion method; spectrophotometric titration; microtitration of sulfate.
Harumitsu Nishikawa*, Hideki Nagasawa and Tadao Sakai**
*Gifu Prefectural Institute of Health and Environmental Sciences, 5-14-12, Yabuta-minami, Gifu 500-8384
**Department of Applied Chemistry, Aichi Institute of Technology, 1247, Yachigusa, Yakusa-cho, Toyota-shi, Aichi 470-0392
A three-channel flow injection(FI) spectrofluorimetric analysis of the total amounts of low-molecular-weight aldehydes in rain water with cyclohexane-1,3-dion(CHD) was developed. The stable baseline was obtained by delivering reagent (0.1% CHD) and buffer(6.6 M CH3COONH4-CH3COOH, pH 5) solutions separately. A reaction temperature of 90°C was necessary for a highly sensitive analysis of aldehydes. The other optimum conditions were: reaction coil length, 0.5 mm i.d.×5 m; cooling coil length, 3 m; sample size, 150 µl; flow rate of the carrier solution, 1.0 ml/min; flow rate of the reagent and buffer solutions, 0.25 ml/min; excitation and emission wavelengths, 376 and 452 nm. The calibration graph was linear in over the range 10~100 ppb of formaldehyde. The relative standard deviation for 10 standard formaldehyde solutions(50 ppb) was less than 1%. This rapid and sensitive FI method was applied for an analysis of the total amounts of aldehydes, calculated as formaldehyde, in rain water. The method is useful for determining water-soluble aldehydes amounts as an index value of organic pollution in rain water.
Keywords: aldehyde in rain water; FIA; cyclohexane-1,3-dion; spectrofluorimetry
Hideaki Kinoshita*, Takeo Chijiwa**, Masaki Torimura, Kenji Kano and Tokuji Ikeda***
*Kwassui Women's College, 1-5, Higashi-yamate, Nagasaki 850-0911
**Nagasaki Municipal Hospital, 6-39, Shinchi-machi, Nagasaki 850-0842
***Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502
The total concentrations of lipoprotein (LP) cholesterol (CR) in serum were directly determined by amperometric measurements of H2O2 generated by polyethylene glycol (PEG)-modified cholesterol esterase and cholesterol oxidase at a membrane-covered, peroxidase-entrapped and ferrocene-embedded carbon-paste electrode. The concentrations of LP aggregators, such as sodium dextran sulfate and MgCl2, and the amount of the PEG-modified enzymes were optimized to determine the high-density lipoprotein (HDL)-CR concentration. The characteristics of the discrimination between HDL and other LPs by the PEG-modified enzymes and the aggregators are discussed. Using a surfactant as a solubilizer of LP aggregation, the HDL- and total CR concentrations have been discriminatively determined. This method was applied to the determination of the HDL-CR values of 17 human samples. The evaluated values were well correlated to those determined by a commercial spectrophotometric determination kit using the PEG-modified enzymes and also by an amperometric determination of the HDL-fraction prepared by an ordinary precipitation method.
Keywords: high-density lipoprotein-cholesterol; total cholesterol; polyethylene glycol-modified enzyme; peroxidase-entrapped and ferrocene-embedded electrode.
Naoko Nonose, Akiharu Hioki, Masayasu Kurahashi and Masaaki Kubota*
*National Institute of Materials and Chemical Research, 1-1, Higashi, Tsukuba, Ibaraki 305-8565
(Received 21 November 1997, Accepted 29 January 1998)In order to establish international traceability in chemical measurements, the Comite Consultatif pour la Quantité de Matié (CCQM) has started interlaboratory studies involving ICP-MS or thermal ionization MS using isotope dilution mass spectrometry (ID/MS) as the reference method for the analysis of simple aqueous solutions containing metal ions. National metrology laboratories participated in these studies. The target level of the relative accuracy for measurements was set at ±1%. In CCQM's 1st study concerning the analysis of six elements in solutions, neither the inherent trueness nor the precision of the ID/MS was achieved by most of the laboratories. In CCQM's 2nd study for the analysis of Pb in a solution, in which a measurement protocol was designed for the ID/MS method, the results were significantly improved, with most participants achieving the target value. The calibration of the mass bias factor with isotopic standard solutions at regular intervals and optimization of the amount of a spike solution added to a sample solution are important for highly accurate analysis using ID/MS.
Keywords: interlaboratory study; isotope dilution; ICP-MS; precision; uncertainty.
Takayuki Abe, Yasuhide Ohuchi and Chikakiyo Nagata*
*Department of Industrial Chemistry, Faculty of Engineering, Shibaura Institute of Technology, 3-9-14, Shibaura, Minato-ku,Tokyo 108-8548
(Received 15 December 1997, Accepted 14 January 1998)13C and 29Si NMR chemical shifts were measured for chloro-, bromo- and iodo-substituted compounds[XnMH4-n; M=C, Si; n=1~4]. Also, the behavior of the chemical shifts for the carbon and silicon atoms in those compounds were investigated. The 13C chemical shifts of chloro- substituted compounds were to a lower field in the order of mono, di, tri and tetrachloro-substituents, which could be explained by an inductive effect. The 13C chemical shifts for iodo-substituted compounds were to a higher field with increasing number of iodine atoms in a molecule. Although the 29Si chemical shifts of chloro- and bromo-substituted compounds were to a lower field in the order of mono and disubsti- tuents, those for tri and tetrasubstituted compounds were to a higher field. The 29Si chemical shift of monoiodo-substituted compound was to a lower field, while the chemical shifts were largely toward a higher field in the order of di, tri and tetraiodo-substituted compounds. This can probably could be attributed to the effect of a steric compression between the substituted iodine atoms.
Keywords: chloro-, bromo- and iodo-substituted compounds; 13C and 29Si NMR chemical shifts.