BUNSEKI KAGAKU Abstracts

We developed a non-contact mode, scanning near-field Raman microscope (NC-SNORM) with a hollow pyramidal probe, using ultraviolet resonant Raman scattering, and measured the stress distribution in very-large-scale integration standards made of silicon dioxide (SiO₂) film and Si, and characterized strained Si/SiGe and Si nanodot structures. The obtained results confirm that our NC-SNORM has a spatial resolution of at least 100 nm. Our NC-SNORM has potential for investigating stresses and structures in Si devices within a short time, and with a penetration depth of 5 nm and a spatial resolution of less than 100 nm.

The reproducibility of measurement results by automated identification and quantification system with a database (AIQS-DB) for GC-MS, which can determine a large number of chemical substances without using their standard substances, has been studied to evaluate the dispersion and to identify the causes of an increase of the dispersion. The reproducibility was examined with 4 GC-MS in 4 laboratories using 114 substances comprising a wide range of physicochemical properties that are difficult to be measured with a GC. As a result, when the performance of a GC-MS passed the designated criteria, the reproducibility of quantification results of 47 substances was almost the same as that obtained by the conventional method that prepares calibration curves before sample analysis. Although the reproducibility of 42 substances was slightly lower than that by the conventional method, the reproducibility is sufficiently reliable, except for in cases that require a high reliability. However, the dispersion of the results of 25 substances was large under the GC conditions used in this study, which indicates that AIQS-DB can only be used as screening for these substances. The causes that affect the dispersion of quantification results are functional groups and the structures of the molecules. The effects of the functional groups are hydroxyl > = amino > nitro group. The effects of the number of them is multiple > single. The position of them can also have different effects : farther > nearer. In the case of the structure of molecules, the effects are as follows : side chain > straight chain > single benzene > multiple benzenes.

An on-line preconcentration method was proposed for the determination of nickel in steels, which is used a part of the iron matrix as a precipitant. In this method, nickel was concentrated during precipitation with ferric hydroxide collected in a Teflon filter tube. A large amount of iron matrix was passed through the Teflon filter tube as a solubility complex by using sodium citrate. Nickel(II) ion that reacted with dimethylglyoxime (DMG) was collected in the Teflon filter tube. As a result, a higher concentration of nickel in iron samples was obtained in the Teflon filter tube. The deposition in the filter tube was dissolved with a nitric acid solution by the on-line flow system. Then, the nickel was reacted with DMG again. The obtained Ni-DMG complex was oxidized with iodine to soluble Ni(III) chelates in aqueous solution. The absorbance of the Ni-DMG complex was measured at 535 nm. The interference of Fe(III) used for the nickel concentration was removed by adding sodium citrate as a masking agent. The calibration curve with a 40-minute concentration operation for nickel was linear over the range of 0 to 500 ppb. The sample flow rate was 1.0 mL/min. The limits of detection and determination for nickel in the sample solution were 1.2 and 3.7 ppb, respectively. The proposed method with 40-minute concentration operation improved the sensitivity 63 times compared to a method without any concentration. With 5-minute concentration operation for nickel, the calibration curve was linear over the range of 0 to 4000 ppb. The limits of detection and determination for nickel in the sample solution were 8.4 and 25 ppb. The proposed method was applied to the determination of nickel in standard steel samples. The results of the determination were in good agreement with the certified values.

Understanding the relationship of stable isotope ratios between polished rice and ambient water provides important strategies for tracing the geographical origin of rice. To identify the correlation of stable isotopic ratios between polished rice and ambient water, oxygen, hydrogen and carbon stable isotopes were examined in ambient water from the Tsugaru plain, Aomori prefecture. The δ¹⁸O and δD values of ambient water samples in the central area of the Tsugaru plain were enriched more than that of the rim of the plain. The slope of the regression equation for the meteoric water line of ambient water samples, 4.95, indicates that the sampled water in the central area of the plain was affected by evaporation. The δ¹⁸O values of polished rice correspond with that of ambient water samples. Thus, the stable isotopes appear to have information about the geographical origin of rice. The δ¹³C values of ambient water have correlations with pH, indicating the possibility that the δ¹³C values depends on the mol ratios of dissolved inorganic carbons. The δ¹³C values of polished rice have no correlation with ambient water samples, which may indicate that the carbon stable isotope are almost all supplied from the atmosphere.

In this paper, we propose two evaluation tools to understand statistical methods related to the z score for use in proficiency testing by interlaboratory comparisons. In the case that the distribution of the test result in the laboratory proficiency testing with a single test item is different from the normal distribution, we propose a new method of the z score based on the lognormal distribution. Because the criteria based on the normal distribution can be adjusted in this case, this technique can be similarly used in interlaboratory comparisons based on two examination materials. When a laboratory uses a method, control charts offer an easy way to keep a running check on work. We consider the simultaneous control of two related variables. For repeatedly performed interlaboratory comparison tests, the Youden approach may provide a useful solution. The simple principle is to test only two nearly identical samples and to compare the difference. However, in many cases there is a large difference in the concentration in examinations that use two examination materials. In such a situation, we consider an alternative approach. We suggest that two variables in which the relations between new variables that measure the bias between laboratories and within laboratory become no correlations are converted. We make a new orthogonal coordinate system. After converting these variables, we construct a new z score on the newly defined orthogonal coordinate system. This z socre is closely related to the control ellipse on the Youden plot.

A catalytic spectrophotometric method for the determination of reactive copper in fresh water has been developed using the copper-catalyzed aerial oxidation of L-ascorbic acid to dehydroascorbic acid (DAA) and the formation of quinoxaline derivatives (QX) by the reaction of DAA with o-phenylenediamine at pH 6.9 and 25°C. The absorbance of QX was measured at 340 nm for a reaction time of 5 min. The calibration curve was linear up to 7 μg L⁻¹ of copper. The detection limits were 0.1 μg L⁻¹ for non-acidified samples and 0.5 μg L⁻¹ for acidified samples. Reactive copper species were characterized as Cu²⁺ and Cu^IIL_i, where i = 1 or 2 for a unidendate and i = 1 for a bidentate ligand (L). The proposed method was useful to estimate reactive copper species, e.g., 40 - 65% as Cu²⁺ and CuOH⁺ in tap water and 10 or 20% as copper complexed with humic substances like fulvic acid in river water. Unreactive copper species were also characterized.

The reverse flow-injection chemiluminescent determination (RFIA) of chromium(VI) was investigated with 4-methoxycoumarin in the presence of hydrogen peroxide and Zephiramine as a cationic surfactant. The chemiluminescent intensity on coumarin and nine kinds of coumarin derivatives were examined using RFIA. As a result, 4-methoxycoumarin was superior to coumarin and other derivatives ; that is, 7-amino-4-methylcoumarin, 3,4-dihydrocoumarin, 5,7-dimethoxycoumarin, 4-hydroxycoumarin, 4-hydroxy-7-methoxycoumarin, 7-methoxycoumarin, 4-methylunbelliferone, umbelliferone. The chemiluminescent strength with chromium(VI) using these detection reagents was amplified after the addition of an alkaline solution. This phenomenon was based on the decomposition of detection reagents with an alkaline solution. The new detection reagent obtained with alkaline pretreatment was coumaric acid from coumarin, for example. The flow system was two channels. The detection of Cr(VI) by the proposed method was 2.1 ppb (S/N = 3). The limit of determination was 6.3 ppb. The conditions for the determination of Cr(VI) were follows : sample solution (line L₂); Cr(VI); flow rate 0.3 mL/min, 1.8% hydrogen peroxide (line L₁); flow rate 0.6 mL/min, Tris solution (pH 9) (line SR); 3.0 × 10⁻³ mol/L 4-methoxycoumarin (50 μL). The proposed method was examined by reverse FIA, because the coumarin derivatives were expensive. Normal FIA also obtained the same result.

A determination method of 4 kinds of tocopherols in soybean oil by high-performance liquid chromatography (HPLC) with ultraviolet detector (UV) on a triacontyl (C30) silica-gel column has been developed. This analytical method provides high linearity of the calibration curve as well as both repeatability and reproducibility. The correlation coefficient of the working curve of calibration were estimated to be from 0.9981 to 0.9998 for 4 kinds of tocopherols in the concentration range from 10 mg L⁻¹ to 100 mg L⁻¹. The limits of detection (LOD) calculated on 3 σ at 10 mg L⁻¹ were 2.0 mg L⁻¹ for α-tocopherol, 2.3 mg L⁻¹ for β-tocopherol, 1.0 mg L⁻¹ for γ-tocopherol, and 0.9 mg L⁻¹ for δ-tocopherol. The limits of quantification (LOQ) calculated on 10 σ at 10 mg L⁻¹ were 6.6 mg L⁻¹ for α-tocopherol, 7.6 mg L⁻¹ for β-tocopherol, 3.3 mg L⁻¹ for γ-tocopherol, and 3.0 mg L⁻¹ for δ-tocopherol. Good results were obtained in recovery tests by using soybean oil. This proposed method could be successfully applied to the determination of 4 kinds of tocopherols in soybean oil.

A simple spectrophotometric method for the determination of pyrroloquinolinequinone (PQQ) was established with N,N-diethyl-p-phenylenediamine in the presence of cerium(III) and cetylpyridinium chloride. In the determination of PQQ, Beer’s law was obeyed in the concentration range of 0.1〜4.0 μg mL⁻¹ of PQQ. The apparent molar absorptivity was 2.72 × 10⁴ L mol⁻¹ cm⁻¹ at 552 nm. The relative standard deviation for five replicate determinations for 2.6 μg mL⁻¹ was 1.14%. The proposed method should be useful for simple determination of PQQ in real samples.