BUNSEKI KAGAKU Abstracts

Hydrate clusters with atmospheric ions have been of long-standing interest in the field of atmospheric sciences, because of their central role in the formation of tropospheric aerosols. A large number of thermochemical studies of the typical positive-ion hydrate clusters, H₃O⁺(H₂O)_n, using mass spectrometry have been reported, while there is little thermochemical information concerning negative-ion hydrate clusters. The absence of information is due to lack of ionization methods for the reproducible formation of specific negative atmospheric ions and their hydrates, and resulting difficulties in obtaining reliable mass spectrometry data from negative-ion hydrate clusters. We have recently established an atmospheric pressure DC corona discharge device that includes a specific needle electrode that leads to the regular formation of various atmospheric negative ions Y⁻. Furthermore, the use of this discharge system coupled to mass spectrometers resulted in the stable formation of large hydrate clusters, Y⁻(H₂O)_n, due to adiabatic expansion caused by pressure difference between the ambient discharge area (760 torr) and the vacuum region in the mass spectrometers (≈ 1 torr). Here, we show the resulting mass spectra of large hydrate clusters, Y⁻(H₂O)_n, with the negative atmospheric ions, Y⁻, such as HO⁻, O₂⁻, HO₂⁻, CO₃⁻, NO₃⁻ and NO₃⁻(HNO₃)₂, which play a central role in atmospheric chemistry. Those reliable mass spectrometry data have provided information about specific cluster sizes having particular thermochemical stability in individual cluster ion series, Y⁻(H₂O)_n, which may correspond to first hydrated shell and magic number for Y⁻(H₂O)_n. Here, we also describe the detailed mechanism of the formation of negative atmospheric ions, Y⁻, and their hydrates, Y⁻(H₂O)_n, in an atmospheric pressure corona discharge ionization mass spectrometry.

The manufacture, import, and use of bis(tributyltin) oxide (TBTO), which is a Class I Specified Chemical Substance under the "Law Concerning the Examination and Regulation of Manufacture, etc. of Chemical Substances," are prohibited in Japan. TBTO could not be analyzed by the methods used for detecting tributyltin (TBT) derivatives because TBTO could not be separated from other TBT compounds, such as TBT laurate, which is a Class II Specified Chemical Substance. Therefore, government agencies cannot regulate products containing TBTO sold on the market. We investigated a mass-spectrometry method for the detection of TBTO by direct sample injection using chemical ionization with isobutane as the reactant gas. Using bis(tributyltin) sulfide as an internal standard, quantitative analysis became more stable. The results of analysis of the resin hardeners by the method developed in this study suggested that TBTO was easily generated by the reaction of dibutyltin dimethoxide with water.

A screening method of organic pollutants in soils has been developed. In this study, we combined a rapid preparation using microwave-assisted extraction and an automated identification and quantification system with a database for GC/MS, which can measure approximately 1000 semi-volatile organic compounds. A sample (3 g) was extracted with a solvent composed of 6 mL of hexane and 4 mL of water at a temperature of 120°C for 30 min. After that, the extract of hexane was cleaned-up with silica gel, NH₂ and carbon adsorbent columns, and then applied to the GC/MS measurement. The total time required for our analytical procedure was approximately 4h. Compared with the conventional Soxhlet extraction method for a soil polluted by organochlorine pesticide, the concentration and the reproducibility by our screening method were comparable, the ratios of the total concentration were in the range of 89 – 138%, and the relative standard deviations were within 11%.

A simple and sensitive method for measuring quinoid polycyclic aromatic hydrocarbons (PAHQs) in soluble organic fraction (SOF) of airborne particles based on two-dimensional high-performance liquid chromatography (HPLC) with fluorescence detection was established. The system involves a reversed phase column with naphtylethyl groups bonded silica packing material for sample clean-up, a 6-port switching valve, an ODS column for trapping the fraction containing PAHQs, a reversed phase column with cholesteryl groups bonded silica packing material for sample separation, and a Pt-Rh catalytic column for the reduction of PAHQs to a corresponding fluorescent compound. The accuracy of the assay, as applied to airborne particulate sample extracts spiked with known amounts of PAHQs were 91 – 107%. The detection limits were 19 to 2000 fmol per injection (signal-to-noise ratio = 3), and the calibration range was from 1 to 100 pmol with excellent proportionality (R²≥0.9992) for four kinds of PAHQs: benz[a]anthracene-7,12-dione, fluoranthene-2,3-dione, pyrene-1,6-dione, and pyrene-1,8-dione. PAHQs in SOF of airborne particles collected in Kyoto, Japan were successfully measured using the established analytical method with simple sample-preparation steps: ultrasonic extraction in organic solvent and concentration under reduced pressure and/or a nitrogen stream.

On-column and on-line redox derivatization methods were developed for enhancing the separation selectivity of HPLC for the analysis of oxidizable and reduciable compounds. On-column derivatization is assisted by the redox activity of a stationary phase packing material such as porous graphitic carbon (PGC) or electrochemically manipulated using an electrochemically modulated liquid chromatographic technique. The analyte compound migrates in the column as a single zone of a mixture of oxidized and reduced forms, so that the retention of the compound is determined by the relative concentrations of the two forms in the column. On the other hand, the on-line redox derivatization system consists of two separation columns and one redox derivatization unit placed between them. The redox reaction proceeds rapidly in the derivatization unit, so that the analyte compound migrates as its original form in the first column, while as its oxidized or reduced form in the second column. The retention of the analytes is thus controlled by the lengths of the two separation columns in this system. A two-dimensional on-line redox derivatization HPLC system was also developed where ‘‘heart-cutting’’ chromatography, in conjunction with on-line redox derivatizaion, was used. This system enables one to isolate specific analytes in complex matrix samples. We have demonstrated that the on-column and on-line redox derivatization methods using porous graphitic carbon as a catalytic redox agent allows the selective separation and determination of cobalt in a manganese nodule and a stainless-steel sample without the interference of metal components coexisting at high concentrations. This technique may find applications in analysis not only of inorganic compounds, such as metal ions, but also of organic or biomolecules.

Recently, the anthropogenic uranium isotope ²³⁶U has been recognized as one of the "environmental uranium (U) isotopes". With the development of instruments and detection techniques of sufficient abundance sensitivity, the applications that use ²³⁶U as a proxy/tool for environmental and geochemical uranium studies are expanding. The origin and level of ²³⁶U in the vicinity area of the Japan Sea were deduced from measurements of ²³⁶U and ¹³⁷Cs in surface soils, seawater, suspended particulate matter and oceanic bottom sediments. This study also presents the feasibility of ²³⁶U use as an oceanic circulation tracer.

Radiocesium released by the Fukushima Daiichi nuclear power plant accident fell in mountainous areas located in northern and western regions of Gunma Prefecture. Therefore, several research groups measured the radiocesium in the sediments in lakes and rivers, as well as soils around rivers, lakes and mountains. In this study, we investigated not only the concentration of radiocesium contained in wasted-sludge samples from a water purification plant, but also the leachate behaviors from the sludge to water. As results, the concentrations of radiocesium in wasted-sludge samples collected from a water purification plant at Kiryu Bureau of Waterworks on 2013 were obviously lower than that on 2011. Additionally, the degrees of radiocesium concentrations were related to those of turbidities in raw water of the water supply. Through leachate tests of radiocesium using aqueous solutions adjusted from pH 2 to pH 10, the risk leaching from wasted-sludge to water was considered to be low without any regard to the pH values of the solutions. Furthermore, the chemical forms of radiocesium in the sludge by a sequential extraction method were expected to mainly exist as residue and oxide forms, which are classified as fractions hardly eluted in nature.

A study was conducted to allow the sorting of coal before import using only a small amount of coal by estimating the amount of leachable Cr(VI). The amount of leached Cr(VI) was determined in eight fly-ash samples from a power plant after extraction with dilute hydrochloric acid (pH 5.8 – 6.3). The Cr(VI)/total Cr ratio varied widely in the range of 0.25 to 5.0% among the coal-ash samples tested. To prepare coal-ash similar to fly-ash from a coal-fired power plant, three coal types were burned in two types of combustion furnaces. One was an experimental furnace with a burner for pulverized coal firing. The leached Cr(VI) concentrations from coal-ash prepared using the experimental furnace were in good agreement with those from a coal-fired power plant, allowing estimates of leached Cr(VI) concentrations from coal-ash prepared in the experimental furnace. The second type was an electric furnace that incinerated pulverized coal on a ceramic dish under an air atmosphere at temperatures from room temperature to a preset value, according to the Japanese Industrial Standard. The Cr(VI) concentration from coal-ash prepared using the electric furnace depended on both the incinerating temperature and type of coal; it was not possible to select an incinerating temperature suitable for all types of coal-ash that had a leached Cr(VI) concentration, in good agreement with that from a coal-fired power plant.

An investigation of the thermal deterioration characteristics of a lithium-ion secondary cell is inevitable for its utilization in electric vehicles. An accelerating rate calorimeter study revealed that a thermal runaway of the cell occurs >130°C. We considered that the analysis of the thermal behavior under high-temperature conditions as well as the thermal runaway is indispensable from the viewpoint of safety, but an analysis of the deterioration behavior in the non-heating domain is essential from the viewpoint of the battery’s lifetime. In this study, in order to analyze in detail the deterioration of the non-heating region, thermal-deterioration characteristics of the lithium-ion secondary cell stored at 70 – 100°C were investigated by varying the state of charge (SOC). To evaluate the thermal-deterioration characteristics, we estimated the activation energy from the discharge capacities before and after a heat hazard. On the other hand, impedance spectroscopy measurements of lithium-ion secondary cells at elevated temperature were carried out to determine the activation energy of charge/discharge, which is determined from the electrochemical parameters by using an equivalent circuit. Based on this analysis, the activation energy of the deterioration is known to be about two-times greater in magnitude than the activation energy of the charge/discharge. The charge/discharge and deterioration reactions are independent of each other; however, a comparison of these activation energies is an important element in order to understand the thermal deterioration of lithium-ion secondary cells that takes place in the non-heating region.