BUNSEKI KAGAKU Abstracts

A portable X-ray diffractometer equipped with an X-ray fluorescence spectrometer was improved so as to obtain a diffraction pattern and a fluorescence spectrum in air from one and the same small area of a specimen. The reason why the portable XRD with an XRF spectrometer was specially designed for archaeology may be understood from the following facts : (1) some objects exhibited in museums are not allowed to be transferred from the open air to a vacuum, even if their volumes are small ; (2) some objects are very difficult to move from their original sites ; (3) some parts of exhibits are extremely fragile and cannot be examined in a vacuum ; and (4) information on the chemical composition and structure from the same area of an object offers a better understanding of the constitutive materials of the object. Some examples of the use of a portable X-ray diffractometer equipped with an X-ray fluorescence spectrometer in the field are also introduced. Experimental results of Sho-kannon, Snew’s mask and Tutankhamun’s golden mask are shown here.

An evaluation of the bio-affinity of methoxo(alkyloxo)- tetraphenylporphyrinatoantimony bromide (1) was examined by an absorption experiment of 1 toward Saccharomyces cerevisiae. An aqueous solution of 1 was added to an aqueous solution of S. cerevisiae. Then an aqueous solution of agar was added into the solution in order to stop the Brownian motion of bacteria during analysis. A prepared aqueous solution containing 1(10 μmol dm⁻³), S. cerevisiae (1.0×10⁴ cells cm⁻³) and agar (0.4 wt%) was taken inside a space surrounded by a silicone spacer (1 cm×1 cm, thickness 50 μm) put on a slide glass, which was set on a confocal laser scanning microscope (CLSM) stage. By measuring the diameter of the cell and the absorbance on CLSM, the concentrations of 1 adsorbed inside S. cerevisia were determined to be 54.2±7.3 for 1a, 49.8±6.2 for 1b, and 22.5±15.5 mmol dm⁻³ for 1c according to Lambert-Beer`s law.

To measure the physico-chemical property upon vaporization, thermal decomposition, and photodecomposition of polybrominated diphenylethers (PBDE), a hyphenated analytical method of headspace/gas chromatography/inductively coupled plasma mass spectrometry (HS/GC/ICP-MS) was developed. Factors that influenced the analytical performance were examined in detail, and the main problem that hindered the application of HS to PBDE analysis was found to be an elevated memory effect. This memory effect was overcome by setting the GC injection port at a high temperature, ca. 400°C, and adopting a pulsed-split injection mode with a split ratio of more than 10 : 1. The repeatability of seven replicate measurements of BDE-209 (405 ng Br in 20 mL vial) was 2.1%. The temperature dependency of vaporization for 13 PBDE congeners, thermal decomposition of BDE-209 in polystylene, and photodecomposition of BDE-209 were measured by the proposed method. This method is superior to the conventional method in the following aspects : 1) evaporation loss of the reactants and products does not take place from the headspace vial during a reaction, 2) every brominated compound, as long as it is vaporized, can be determined with equimolar sensitivity by GC/ICP-MS, and therefore, 3) the mass balance of the reaction can be calculated.

A high-sensitivity, high-precision analytical method was developed to determine trace amounts of boron in silicon or germanium semiconductor materials. Silicon was dissolved with a mixture of hydrofluoric acid and nitric acid, while germanium was dissolved with aqua regia. In order to prevent boron from being vaporized by heating in hydrofluoric acid, phosphoric acid and sulfuric acid were added to the solution. After the sample solution was thoroughly dehydrated by heating, silicon was vaporized as SiF₄ ; however, germanium remained as a white precipitate (GeO₂). By the addition of methyl alcohol to the dehydrated sample solution and subsequently heating it, boron could be separated as methyl borate from the sample solution. The resulting methyl borate was absorbed in a sodium hydroxide solution, and then boron was determined by a curcumin spectrophotometric method. The recoveries of boron after distillation were almost 100% in both silicon and germanium. The detection limit of boron was 0.1 ppm in silicon and germanium.

The determination of total nitrogen in vinegar (komekuro-zu) by the Kjeldahl method was studied for a revision of the Japanese Agricultural Standard (JAS). Based on the previous JAS analysis, optimization was performed for the Kjeldahl method using either an electric heating device and a traditional distillation system, or a digestion block instrument and a steam distillation unit. The optimum digestive conditions were examined including the volume of sulfuric acid, the amount of potassium sulfate, the volume and the addition method of a 30% hydrogen peroxide solution, the types of catalysts, and the heating period after the liquid became clear. The optimum conditions for the digestion of vinegar involved the addition of 2 catalyst tablets (9.0 g K₂SO₄, 1.0 g CuSO₄ · 5H₂O), 15 mL of sulfuric acid, and 10 mL of a 30% hydrogen peroxide solution. In digesting the vinegar, the heating period after the liquid became clear was determined to be 120 min by the electric heating device and 90 min by the digestion block instrument. This method yielded high recoveries of nitrogen from lysine-HCl (more than 97%), and a lower RSD of total nitrogen in vinegar (1.0% or less). This method was more convenient than the previous JAS method, by making block digestion and steam distillation available.

We developed a simple electrochemical device for transferring DNA (deoxyribonucleic acid) from DNA printed matter onto filter paper (5 mm×10 mm) without spoiling the DNA printed matter. The device is composed of a pair of pin-shaped electrodes, an electrode stand and a compact stage. Extracted DNA from the filter paper was amplified by PCR (polymerase chain reaction), and detected. Various transferring conditions (i.e., kinds of moisture solvent, applied voltage and contact time) were optimized. We confirmed that an excess voltage and a longer contact time caused the decomposition of DNA. When we used TBE buffer (Tris-Borate EDTA) as a moisture solvent, the optimum applied voltage was 10 V, and the contact time was 60 seconds.

A new improved double-chamber electrothermal vaporization (ETV) system has been designed. An inner chamber made of quartz glass was attached with an inlet port to an inductively coupled plasma (ICP) torch. The inner chamber has an important role to introduce metal vapor in a 1.0 kW argon ICP. Ten microliters sample aliquots were dried at 90°C and subsequently heated at 1300°C on a tungsten boat furnace. The released vapor was swept into the ICP source through PTFE tubing and the inner chamber by 0.6 L min⁻¹ H₂ (7%) - Ar carrier gas. The performance parameters of ETV-ICP-AES, such as the temperature program, gas flows and position of the inner chamber, were evaluated by using a cadmium standard solution. Under the optimized stop and flow experimental conditions, the best attainable detection limit at Cd I 214.43 nm line was 0.2 ng mL⁻¹ with linear dynamic ranges of 10 to 10000 ng mL⁻¹ for cadmium without modifiers. The instrumental precision, expressed as the relative standard deviation (RSD) from ten replicate measurements of 10000 ng mL⁻¹ for cadmium by ETV-ICP-AES, was 0.85%. The detection limit and RSD were improved by 3 times over that reported by Okamoto. The present method has been applied to the determination of cadmium in water and plant samples.

The electrode catalyst of a fuel cell is an important component because it is the electric generating part of the cell. The authors carried out a long-term durability test of a PEFC electrode using 6 test cells with a Pt-Ru alloy for the anode catalyst and a Pt-Co alloy for the cathode catalyst. During 12000 hours of cell operation, electrochemical measurements were conducted at 1000 hour intervals. The cells were disassembled after 0 (initial), 3600, 6200, 9000, 11200 and 12000 hours of operation to observe the electrode components. By analyses of the electrode materials, such as a change in a particle of the electrode catalyst, dissolution of the alloy catalysts, catalyst migration to the electrolyte membrane, and a change in the amount of electrolyte ionomer, the relationship between the material change and the cell deterioration was revealed.

National Metrology Institute of Japan (NMIJ) has developed certified reference materials (CRMs) of CF₄ and SF₆ in N₂. These CRMs correspond to primary reference gas mixtures in Japan. The nominal concentration of CF₄ or SF₆ is 5 mmol/mol and its concentration corresponds to concentration level of gas analyses at the system of semiconductor process tools. In the first procedure for developing this CRM, the five primary gas mixtures were prepared using high-accuracy electronic mass comparator (maximum capacity, 15 kg, readability, 1 mg) with handmade automatic cylinder exchanger, for gravimetric blending method. The prepared mixtures were verified by analysis adopting a gas chromatograph with a thermal conductivity detector (GC-TCD), a quality control cylinder, and, Deming’s least squares method for linear regression analysis. This verification (internal consistency test) confirmed that there was no mistake in the process of the preparation within the accuracy of GC-TCD. The relative standard uncertainty of the response of GC-TCD was 〜0.03%. After that, the long-term stability test for 47 months was performed and the dependence of inner gas pressure in a cylinder from 11 MPa to 1 MPa was evaluated. The relative expended uncertainty of this CRM became 0.2 to 0.3%, which included the uncertainties estimated from results of the preparation, the internal consistency test, a long-term stability test, and, an inner pressure dependence test. This expanded uncertainty is sufficiently small for users of this CRM.