BUNSEKI KAGAKU Abstracts

Microscopic structures in aqueous alcohol and aqueous acid solutions were studied through mass spectrometric analyses of clusters generated by the fragmentation of liquid droplets. For water-alcohol binary mixtures, the self-association of alcohol molecules was found to be related to their physicochemical properties, such as the viscosity, phase separation and preferential solvation. The molecular self-association of alcohol induced by the coexistence of water was explained by the relativity of the intermolecular interaction energies led by the mixing of water with alcohol. For aqueous acid solutions, cluster structures in aqueous nitric acid, sulfuric acid and acetic acid solutions were found to reflect their acidity in water, that is, the ionization efficiency. Furthermore, the neutralization of acetic acid by sodium hydroxide to form sodium acetate was observed as a change of the cluster-level structure.

The application of LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) to the chemical characterization of single trunk mat fibers made of PET was investigated in order to establish a forensic analytical method for the discrimination of samples of different origins. The analytical conditions of LA-ICP-MS equipped with a 213 nm Nd : YAG laser were optimized to analyze trace elements, such as Cu, Sb, and Ba at ppm levels. A total of 31 samples produced by 7 car manufactures in Japan were used for analysis. The concentrations of Li, Mg, Al, P, Ca, Ti, Co, Cu, Ge, Nb, Sb, Ta, and Pb were successfully measured from a single fiber sample with a diameter of ca. 20 μm. It was possible to discriminate all 31 samples based on the analytical results of a single fiber by LA-ICP-MS combined with those of FT-IR and SEM-EDS. LA-ICP-MS has good analytical sensitivity, and requires a much shorter preparation time and a smaller sample size than any other conventional element analysis methods. This paper demonstrates for the first time that this method is practically useful as a powerful tool for the forensic identification of a single trunk mat fiber.

Fluorescent probes are powerful tools to understand the biological roles of biomolecules because they can provide both temporal and spatial information of the target biomolecule in living cells. To date, many fluorescent probes, such as fluorescent probes for the detection of metal ions, have been developed. However, the fluorescent probes we have are still not sufficient due to the multiplicity of biomolecules. We have developed several chemical fluorescent probes for the detection of reactive oxygen species (ROS) and proteins. In this review, we focused on the fluorescent probes reported by our group. The design and the basic performance of the probes were highlighted.

An interlaboratory study was conducted to evaluate the reproducibility of the combustion method for determining crude protein in corned beef. Five laboratories analyzed five test materials each (five pairs of blind duplicates) of corned beef by the combustion method. After removal of statistical outliers, the repeatability (RSD_r) and reproducibility (RSD_R) of this method were found to be 0.36〜1.7% and 1.3〜2.0%, respectively. The HorRat values of this method were 0.38 to 0.58. The interlaboratory study on crude protein in corned beef by the Kjeldahl method in the Japanese Agricultural Standard (JAS) was performed simultaneously, using the same test materials. The results for the combustion method were compared with those for the Kjeldahl method. For four of the materials, differences of means between the two methods under reproducibility conditions were within critical difference at the 95% probability level. The difference of 0.33% for the one remaining material did not affect judgment of the standard value 21% of the JAS. The present study demonstrates that the combustion method has acceptable precision.

The price of iron ore is decided depending on the content of total iron. A large amount of iron ore is traded at a time at a steel maker. Therefore, a high-precision and rapid analytical method is demanded. A precision determination method of iron based on rapid complex formation has been investigated by a stopped-flow spectrometric method. Ammonium thiocyanate was selected as a detection reagent. The sample solution was prepared with a HCl solution after alkali fusion with a mixture sodium carbonate and sodium peroxide. The concentration of chloride ion was adjusted to under 0.1 mol/L in the final solution. The average of fifty points in the range of 0 to 0.2 second was obtained as one measurement result. Furthermore, the 7 results were used for data of an RSD (%) calculation. The optimum conditions of iron determination by the present method were as follows : pH of sample solution (250 μL), 1.6 ; pH of 6.2 mol/L ammonium thiocyanate (250 μL), 5.0 ; measurement time, 0〜0.2 s ; results. The iron in a sample cell was determined over the range of 7 to10 ppm by measuring a complex of iron at 480 nm. The analytical time for one sample solution was 1 minute including cleaning time of the reaction line. As a result, four significant figures on the Fe content (%) could be obtained as the result of an analysis by the present method. The results of Fe determination in standard iron ores showed good agreements with certified values.

The elution behaviors of ethylene-vinyl acetate copolymer (EVA) with different composition were characterized by gradient high-performance liquid chromatography. In this study, EVA samples having a narrow molecular-weight distribution containing vinyl acetate (VAc) from 18 wt% to 80 wt% were prepared by size exclusion chromatography for fractionation. EVA samples were eluted depending on the VAc content without depending on the molecular weight with a linear gradient from 100% acetonitrile to 100% chloroform. The relation between the VAc content in EVA and the composition of chloroform in the eluent at the time of EVA eluting indicated a good correlation, and the composition of chloroform in the eluent agreed with the critical adsorption point in the chloroform and acetonitrile eluent.

Eight kinds of municipal solid waste incineration fly ash and two kinds of molten fly ash were analyzed for the speciation of cadmium by a sequential extraction procedure, a pH-dependent test and X-ray absorption fine structure (XAFS). Concerning the result of XAFS, cadmium in fly ash was represented with CdCl₂ : 94% + Cd : 6%. When the pH in the water-soluble fraction of the sequential extraction procedure is highly alkaline, it is presumed that CdCl₂ is dissolved, and then precipitates in the form of Cd(OH)₂, which is dissolved in the form of an ammine complex in the AcONH₄ fraction of the sequential extraction procedure. When the pH in the water-soluble fraction is neutral, CdCl₂ is dissolved and does not precipitate. The experimental result of sequential extraction, pH-dependent test and XAFS were consistent with modeling by Visual MINTEQ.

Bromide compounds in tap water were measured by using a hyphenated technique of ion chromatography coupled with inductively coupled plasma - mass spectrometry (IC/ICP-MS) and electrospray ionization mass spectrometry (ESI-MS). We identified bromide ion (Br⁻), bromate ion (BrO₃⁻), bromochloroacetic acid (BCAA), dibromoacetic acid (DBAA) and bromodichloroacetic acid (BDCAA) by standard addition methods with IC/ICP-MS. Moreover, we identified BCAA and BDCAA by ESI-MS after separation with IC. Br⁻, BrO₃⁻, BCAA, DBAA and BDCAA in tap water collected from around Tokyo area were quantified by IC/ICP-MS. The maximum concentration of BrO₃⁻ (1.8 ng mL⁻¹) was observed in tap water collected from Bunkyo-ku, although this concentration was lower than 10 ng mL⁻¹, which is the regulated concentration in Japan. DBAA, which is regulated by United States Environmental Protection Agency, was detected in tap water collected from all sites, except for Ome. However, scince BrO₃⁻ and DBAA are toxic, it is necessary to continue monitoring bromide compounds in tap water.

The solution produced in the anolyte compartment by the electrolysis of a dilute NaCl solution, ie., acidic electrolyzed water was analyzed by a gas chromatograph/mass spectrometer (GC/MS). As a result, organochlorinated compounds that are derived from constitutional materials of electrolytic compartments, and silicone compounds originated from O-ring of electrolytic compartments were detected. We examined the surfaces of ABS resin and a diaphragm, which were immersed in acidic electrolyzed water for 4 weeks, by scanning electron microscopy, slight changes of the surfaces were observed. It is likely that acidic electrolyzed water that contains free chlorine deteriorates constitutional materials of electrolytic compartments.

The analysis of amino acids is becoming important in a variety of application fields ranging from food analysis to protein science. A number of separation and detection methods are currently used. Among them, combination of precolumn derivatization with dabsyl chloride and separation on a C18 column with UV/VIS detection is generally preferred due to simplicity, excellent stability, good reproducibility and high sensitivity of the method. Although OPA (orthophthalic aldehyde) is very popular derivatization reagent, it reacts with only primary amino acids. On the other a hand, dabsyl chloride forms derivatives for both primary and secondary amino acids. Conventional methods use a 4.6 mm I.D. × 150 − 250 mm column with 5 μm particle size packing material that requires approximately 45 min to complete the analysis. We evaluated the ability to shorten the analysis time by using an ultra high-performance liquid chromatography (UHPLC) system with a 3.0 mm I.D. × 50 mm column packed with 1.8 μm particle size packing material. Our results show a reduction of the total analysis time from 45 min to 7.5 min. We also report examination results of pre-column reactions as well as an outline of the separation conditions and several applications for this rapid separation method.

The speciations of heavy metals (Cu, Zn, Pb, Cd and Cr) in bottom sediment soils collected from Kusaki dam-lake in Gunma Prefecture were considered to be in the solubility with the type of ligands, by a sequential extraction procedure with five fractionations. Through these procedures, a large amount of Cu in Kusaki dam-lake sediment was in a fraction bound to organic matter ; those of Zn and Pb were in an oxide fraction bound to iron and manganese oxides, and those of Cd and Cr were in the exchangeable fraction and in the residual fraction, respectively. The composition of species in a heavy metal was almost the same without any regard to the collection periods for two and a half years, the particle size of the sediment soils and the collection points. The total concentrations of heavy metals in the sediment soil at Kusaki dam-lake was still high at this stage, compared with those at Kanto loam and Black soil (Kurobokudo). From the distributions of each fraction for analyte heavy metals, the ratios of heavy metals with long-term leaching were estimated.