BUNSEKI KAGAKU Abstracts

Vol. 53 No. 2

February, 2004

Accounts

Development of a standard sample preparation method for total-reflection X-ray fluorescence analysis and its semiconductor applications

Yoshihiro Mori¹ and Kenichi Uemura¹

(Received 2 October 2003, Accepted 19 November 2003)

Total-reflection X-ray fluorescence analysis (TXRF) has come into wide use for contamination control in the production of semiconductors. One of the problems in conducting quantification and cross-check experiments of TXRF is the issue of standard sample preparation. The signal intensity of TXRF greatly depends on the depth-profile of the analyte, and the depth-profile reproducibility of traditional standard sample preparation methods was sometimes not satisfactory. In this paper, a new standard sample preparation method that utilizes chemisorption in an alkaline hydrogen peroxide solution is presented. The method showed good reproducibility of the depth-profile as well as spatial and wafer-to-wafer uniformity. The standard wafers prepared by this method were actually applied for quantitative analysis and cross-check experiments, and the results were quite promising.

Keywords : total-reflection X-ray fluorescence (TXRF) analysis; semiconductor surface characterization; trace contamination analysis; reference standard sample; cross check.

Research Papers

Flow-injection spectrophotometry of zinc by an on-line concentration method using a glass capillary tube

Kunihiro Watanabe¹, Ryoma Yamamoto¹ and Masayuki Itagaki¹

(Received 10 September 2003, Accepted 4 November 2003)

A new concentration on-line system for Zn(II), Cu(II), Pb(II) and Cd(II) determination was developed. The method is based on the adsorption of metals on the inner surface of glass capillary tubes. The metal ions that were concentrated on a glass surface for 5 minutes were eluted on-line with a small amount of dilute nitric acid solution in the carrier line. The flow system was composed of four channels, including the carrier, sample solution, buffer solution and detection reagent. The concentration efficiencies of Zn(II), Cu(II), Pb(II) and Cd(II) obtained by the present method were about 166, 143, 394 and 102 times, respectively. Further, the eluted metal ions were then determined with 4-(2-pyridylazo)resorcinol (PAR) by spectrophotometry. The optimum conditions by the present method were as follows: buffer solution, pH 9.0(Zn), pH 9.0(Cu), pH 8.5(Pb), pH 9.5(Cd); PAR, 4.0×10^-4 M, pH 10; eluent HNO₃, 3.0×10^-2 M 20 µl; R.C. length, 1.0 m(Zn), 0.1 m(Cu), 1.0 m(Pb), 0.2 m(Cd); wavelength: 493 nm(Zn), 517 nm(Cu), 520 nm(Pb), 504 nm(Cd). The detection limits of Zn(II), Cu(II), Pb(II) and Cd(II) were 0.076 ppb, 0.12 ppb, 0.69 ppb and 0.25 ppb, respectively. The sensitivities of Zn(II), Pb(II) and Cd(II) obtained by the present method were superior to that of the Teflon-tube method as a conventional method. The present method was successfully applied to the determination of trace Zn(II) in tap water after masking Cu(II) and Fe(II) with sodium thiosulfate, Cd(II) with potassium iodide, and Mn(II) with triethanolamine, respectively.

Keywords : on-line concentration; glass capillary tube; Teflon tube; zinc determination by FIA; PAR.

Measurement of NIR-SERS using commercial silver powder

Taro Uchida¹ and Seiichiro Higuchi¹

(Received 18 August 2003, Accepted 16 November 2003)

A new method has been proposed for easily obtaining the NIR-SERS spectrum using a commercial silver powder. The utility of this measurement method for enhanced Raman spectra due to the existence of silver particles for some compounds is presented. About 10 times enhancement was obtained by this method when compared with a usual Raman spectrometry. It was sufficiently sensitive for a quantitative determination of diluted samples. The spectral features of the method contrasts were considered in terms of a existence of different conformations of substituents.

Keywords : near infrared; FT-SERS; commercial silver powder; structural analysis; conformational isomers.

Determination of glycation on diabetic erythrocytes by electromagnetophoresis

Osamu Nozaki¹, Motonori Munese² and Hiroko Kawamoto³

(Received 22 July 2003, Accepted 24 November 2003)

A novel determination method for assaying glycation on erythrocytes by electromagnetophoresis was developed in this study. The prediction of angiopathy is necessary for treating diabetic patients, because the major cause of death of diabetic patients (type 2) is due to angiopathy. The levels of the fasted blood glucose and glycated hemoglobin A1c (HbA1c) are assayed for daily laboratory tests, but do not reveal the damage to the cells or vessels of diabetic patients. The aim of this study was to develop a novel method involving the electromagnetophoresis of diabetic erythrocytes. The method consisted of two steps. One was to bind boric acid-induced magnetic beads to a glycated membrane of erythrocytes; the second was to separate the complex of the erythrocytes and the magnetic beads by using an electric force for migrating the complex and a magnetic force for restricting the migration of the complex. We synthesized boric acid-introduced magnetic beads for this study. We chose 300 Gauss for the external magnetic force. A comparative study of the migration of erythrocytes by electrophoresis and electromagnetophoresis revealed a shorter migration of the erythrocytes by electromagnetophoresis than by electrophoresis, because the electrophoresis of erythrocytes reacted to the surface charge, and the electromagnetophoresis surface glycation of the erythrocytes. The electromagnetophoresis of the erythrocytes with values of HbA1c ranging from 5.4, 7.7, 8.6 and 9.3% resulted in a shorter migration of the erythrocytes in corporation to increase of the values of HbA1c. This meant that the method by elelctromagnetophoresis was successful for assaying glycation on erythrocytes, and will be a possible method for assessing the diabetic disturbance on cells.

Keywords : glycation; erythrocyte; diabetes mellitus; electromagnetophoresis; boric acid-induced magnetic beads; electrophoresis.

Determination of U and major elements in Lake Biwa water and its inflow river water by ICP/three dimensional quadrupole mass spectrometer

Hideyuki Sakamoto¹, Kazuko Yamamoto¹, Toshihiro Shirasaki¹ and Hideo Yamazaki²

(Received 12 September 2003, Accepted 26 November 2003)

An analytical method for the rapid determination of major elements (Na, K, Ca, Mg) and U at the ultra-trace level in river and lake water samples was developed by ICP/three dimensional quadrupole mass spectrometer (ICP/3DQMS). The optimum analytical scanning condition of ICP/3DQMS, the dependency of the buffer gas pressure at 3DQMS on the ion signal intensity, and the effect of the matrix-element concentration on U at the trace level were investigated. As a result, the detection limit (3σ) of U by this method was 0.7 ng/l. The proposed method was applied to the determination of Na, K, Ca, Mg and U in Riverine water (NRC·CNRC SLRS-4) and Lake Biwa water as well as the 13 rivers water of flowing into the lake. The analytical result of U in Riverine water was in good agreement with the certified value. The analytical results of Na, K, Ca and Mg in Lake Biwa water and the water of 13 rivers flowing into the lake were in good agreement with the values obtained by ICP-OES. The concentration of Ca in the water of 13 rivers flowing into the lake reflected the surrounding geological features. The uranium concentration was high at the north eastern district of Lake Biwa. The average contents of the Lake Biwa surface water were 8.3 mg/l for Na, 2.28 mg/l for Mg, 1.48 mg/l for K, 12.1 mg/l for Ca and 22.0 ng/l for U. The vertical distribution of U in lake Biwa water changed with the water column depth.

Keywords : Uranium; Lake Biwa; ICP/three dimensional quadrupole mass spectrometer.

Adsorption of divalent heavy metal ions on calcium carbonate (calcite)

Hitomi Kobayashi¹, Keiichi Satoh² and Kiyoshi Sawada²

(Received 21 May 2003, Accepted 14 December 2003)

The adsorption of divalent heavy metal ions, M²⁺(Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺), on a calcite surface was investigated at 25.0°C. The concentrations of metal ions in solution (C_M) and on calcite surface (C_M,S) were determined by ICP-MS. The slopes of plots of log D (D=C_M,S/C_M) as a function of pH were obtained as 2 for Cd²⁺ and Pb²⁺, whereas those for Co²⁺ and Zn²⁺ were between 1 and 2. The distribution ratio of these ions dose not depend on the calcium concentration. An analysis of the results by taking into consideration the formation of the hydroxo complex of the metal ions in solution revealed that the chemical species adsorbed on a well-developed calcite surface are M(OH)₂. On the other hand, the distribution ratio of Cu²⁺ dose not depend on the pH, and increases upon decreasing the calcium comcentration. Thus, the adsorbed species was estimated to be Cu(CO₃). The adsorption of neutral species prevents the accumulation of positive charge of the crystal surface, and minimizes the electrical repulsion between the surface and adsorbing species. The distribution ratio on a rough surface created by grinding the calcite crystal was also studied. The distribution ratio on the rough surface was higher by 1-2 orders than that of the smooth surface.

Keywords : adsorption; calcite; heavy metal; crystal surface.

Technical Papers

Determination of trace elements in certified reference material of human urine by instrumental neutron activation analysis

Shogo Suzuki¹, Yukiko Okada¹ and Shoji Hirai¹

(Received 15 April 2003, Accepted 4 December 2003)

Trace elements in a certified reference material of human urine prepared at the National Institute for Environmental Studies (NIES) of Japan were determined by instrumental neutron activation analysis (INAA). Twelve aliquots of NIES No.18 human urine samples (2.5 ml) were freeze-dried at -50°C. The dry residues and comparative standards were irradiated for a short time (10 s) at a thermal neutron flux of 1.5×10¹² n cm^-2 s^-1 (pneumatic transfer) and for a long time (6 h) at a thermal neutron flux of 3.7×10¹² n cm^-2 s^-1 (central thimble) in the Rikkyo University Research Reactor (TRIGA Mark-II, 100 kW). The irradiated samples were measured by conventional γ-ray spectrometry using a coaxial Ge detector, and by anti-coincidence γ-ray spectrometry with a coaxial Ge detector and a well-type NaI(Tl) detector. The concentrations of 15 elements (Na, Mg, Cl, K, Co, Ni, Zn, As, Se, Br, Rb, Sr, Mo, I, Cs) were determined by these methods. The determined values were in good agreement with the certified values of 3 elements (As, Se, Zn).

Keywords : determination of trace elements; instrumental NAA; environmental reference material; NIES No.18 CRM human urine; γ-ray spectrometry.

Ion exchange separation of trace amounts of iron in high-purity copper for graphite-furnace AAS

Masahiro Yokoi¹, Takashi Ishiyama¹ and Tatsuhiko Tanaka¹

(Received 1 May 2003, Accepted 11 December 2003)

A simple and selective ion-exchange preconcentration technique is described for the graphite-furnace atomic-absorption spectrometric determination of trace amounts of iron in high-purity copper. Iron(III) was separated from large amounts of copper(II) by complexing iron(III) with sulfosalicylate, followed by passing the solution through a chloride-form anion-exchange column (Dowex1-X8, 3 ml) at a flow rate of about 5 ml min^-1 in a 0.02 M chloride medium (pH=3.2). The column was washed with 10 ml of 0.02 M hydrochloric acid, and then the adsorbed iron(III)-sulfosalicylate complex was eluted from the column with 10 ml of 2 M nitric acid. After anion-exchange separation, the iron contents were determined by GFAAS. Iron(III) could be quantitatively adsorbed on a small column (13 mm i.d. and 30 mm bed length) up to 200 ml of a sample solution. The calibration graph prepared with the standard iron(III) solution was linear over the concentration range of 1~50 ng ml^-1 with a relative standard deviation (n=3) of 1.2% at 10 ng ml^-1. The proposed method was applicable for determinations down to 0.16 µg g^-1 of iron in copper with a preconcentration factor of 20. Such elements as Ag, Al, Bi and Sn were also adsorbed on the column, but the maximum permissible concentrations of these elements exceeded the concentrations normally found in high-purity copper. The optimized method can be applied to the determination of iron at the µg g^-1 level or lower in high-purity copper samples with a recovery of more than 99%. The time required for an analysis was within 3 h.

Keywords : iron determination; copper analysis; ion-exchange preconcentration technique; iron(III)-sulfosalicylate complex; graphite-furnace atomic absorption spectrometry.

Notes

Mechanism of salt error on the color development of phosphomolybdenum blue

Hirokazu Kobayashi¹ and Eiko Nakamura²

(Received 27 August 2003, Accepted 7 November 2003)

The molybdenum blue method, a widely used method for the determination of phosphate, is based on the formation and reduction of 12-phosphomolybdic acid, in which ascorbic acid with antimony(III) and tin(II) chloride function as a reductant. In the method, chloride ion in the sample affects the color intensity of the produced molybdenum blue. This phenomenon is called the salt error. The levels of the salt error are known to be less when ascorbic acid with antimony(III) is used compared to when tin(II) chloride is used. The present study examined the difference between ascorbic acid with antimony(III) and tin(II) chloride at levels of the salt error observed in molybdenum blue formation. Molybdenum blue reduced by ascorbic acid with antimony(III) or tin(II)chloride was extracted into MIBK, and the amounts of antimony or tin in the MIBK phase were determined by AAS. The atomic ratios of antimony to phosphorus and tin to phosphorus were determined. When 12-phosphomolybdic acid was formed from 30~50 µg of phosphate-phosphorus and reduced by ascorbic acid with antimony(III), the antimony to phosphorus ratio was found to be ca.2 in the presence and absence of chloride ion in a sample. Under the same condition, when tin(II) chloride was used, the amounts of tin in the MIBK phase decreased as the chloride ion concentrations of the sample increased, with tin to phosphorus ratios being ca.2 at 0% of chloride ion, and ca.0.7 at 5% chloride ion. The results indicate that chloride ion in a sample reacts with tin(II) forming a complex,thereby, chloride ion interferes with tin(II) associating with molybdenum blue. Meanwhile, because the chloride ion does not form a complex with antimony(III), antimony(III) can associate with molybdenum blue regardless of the presence of the chloride ion.

Keywords : phosphomolybdenum blue; salt error on molybdenum blue method.

Relationship between the metal contents and the chlorophyll SPAD values in dried sea laver

Toshiko Nagahama¹, Jinghua Zhang¹, Hiroki Ohwaki², Yasuhiro Ishibashi³, Yuji Fujita⁴ and Sunao Yamazaki¹

(Received 9 May ²⁰⁰³, Accepted 4 December 2003)

To evaluate the relationship between the metal and chlorophyll contents in dried sea lavers (nori), analyses of metals by ICP-AES and chlorophyll content by a Minolta chlorophyll meter, as expressed by the SPAD value, were performed. Seventy dried sea laver samples including color fading lavers were products from Ariake Sea. The correlations between the contents of Fe, Zn, Mn and the SPAD values was confirmed with the coefficient (R) being 0.774, 0.707 and 0.564, respectively. It was suggested that the SPAD value could be applicable to evaluate the quality of dried sea lavers.

Keywords : chlorophyll; nori; sea laver; SPAD; trace metals.

Technical Letters

Dissolution method for LixKCa2Na2Nb5O16 superconductor compounds in inductively coupled plasma-optical emission spectrometry

Mikio Ishikuro¹

(Received 27 October 2003, Accepted 4 December 2003)

Proper dissolution procedures for perovskite-type niobium oxide compounds were investigated for an elemental determination in inductively coupled plasma-optical emission spectrometry (ICP-OES). Niobium oxide compounds are usually decomposed by using several kinds of fluxes. However, flux compounds, such as sodium disulfate (Na₂S₂O₇) and potassium hydrogensulfate (KHSO₄), are not employed for LixKCa₂Na₂Nb₅O₁₆, because these fluxes contain sodium or potassium. This paper describes a new dissolution method with an acid mixture that is suitable for the analysis of Li_xKCa₂Na₂Nb₅O₁₆ samples by ICP-OES. The samples were not decomposed with H₂SO₄ only nor with HF-HNO₃. However, they were able to decompose with an acid mixture of HF-HNO₃-H₂SO₄. Also, in a microwave-assisted dissolution method, the samples were completely decomposed only when a ternary acid mixture was employed.

Keywords : Li_xKCa₂Na₂Nb₅O₁₆ superconductor compounds; dissolution method; mixture of HF-HNO₃-H₂SO₄; ICP-OES.

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