BUNSEKI KAGAKU Abstracts

It was considered that capillary columns showed a high separation efficiency, based on a restriction of the analyte diffusion. However it had been thought that it is difficult to prepare for a capillary column with good repeatability and durability. We have developed 5 different preparation procedures for capillary columns, which use silica matrices for fixing packed particles or proteins. The five procedures have their own features, respectively and it is necessary to choose the procedure properly based on the purpose. For example, a particle-loaded column is suitable for obtaining a better separation efficiency with a similar separation property of a commercially available LC column. A protein-encapsulated column made by a sol-gel method was suitable for the preparing a highly selective column for the separation of small biomolecules. We hope that the developed columns will be used for a variety of research fields.

We found a phenomenon that the application of a voltage to a capillary column can vary the retention factor of both ionic and neutral analytes in pressurized flow driven capillary electrochromatography (pCEC). Studies of this phenomenon revealed that the retention variation depended on the magnitude of the applied voltage, its sign, and the kind of analytes. The change in the surface charge under an electric field has an important role on the retention variation. In the case of separating alkyl benzenes in an ODS column, the applied voltage changed both entropy and enthalpy of transfer of an analyte from the mobile phase to the stationary phase. However, the entropy-enthalpy compensation canceled any voltage-induced variation of the retention factor. A new injection method based on a retention variation is proposed in which the pulsed voltage was applied to the column with continuous supplying a sample solution. Furthermore, we found that the application of an alternating voltage to a capillary column can also vary the retention factor of a sample solute. The alternative voltage capillary electrochromatography (AV-CEC) was developed as an application of this phenomenon to control the retention of a sample solute. The retention factor varied according to both the amplitude and frequency of an applied alternating voltage and the variation greatly depended on the kinds of sample solutes and the packing materials.

We studied ultrafine particles with particle sizes under 100 nm in suspended particulate matter that existed in a real environment. Ultrafine particles may have a serious influence on human health. There are many papers concerning their influence on human health based on animal tests that involved exposing ultrafine particles or performing a mass concentration assessment by a lumpling analysis. However, information concerning individual ultrafine particles is not enough. By introducing individual analysis using the EPMA method, we estimated a collection plate, which was unsuitable to collect and to analyzing ultrafine particles. The purpose of this study was to obtain detailed information about ultrafine particles, including trace-element detection. Important information of ultrafine particles includes not only the chemical conformation, but also the shapes of individual particles. The shapes of individual particles were observed by a high-resolution SEM equipped with aberration correction for fine-particulate imaging. From the results, we could obtain detailed information about ultrafine particles concerning their composition and shape with nano-dimensions. The high-resolution SEM image included precise information about the origin and fate of ultrafine particles. This method suggests another estimation method for ultrafine particles.

The author attempted to estimate environmental polychlorinated biphenyl (PCB) pollution factors using principal-component analysis, cluster analysis, and 3 kinds of chemical mass balance models (CMB8, Mr-CMB, Fr-CMB), based on detailed pattern data obtained from comprehensive congener analysis of PCB. In the principal-component analysis and the cluster analysis, 4 kinds of kanechlors and combustion-caused samples were identified, and the congener patterns were characterized. Next, based on the results, the author calculated the contribution rate of each PCB pollution factor in various environmental samples with CMB8, Mr-CMB and Fr-CMB, and compared and evaluated the analysis results of CMB. As a result, the estimated contribution rates were almost the same, and the results indicated the characteristics of the target samples accurately.

The Japan Society for Analytical Chemistry has developed a synthesized wastewater certified reference material (CRM) for the determination of polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs) and dioxin-like polychlorobiphenyls (DL- PCBs). Bottom ash of a waste incinerator was pulverized into fine particles and mixed well with commercial sterilized underground water (for drinking) to make a thick suspension. The exact volume of this suspension was taken and diluted with nearly 3 kg of water, as mentioned above. By controlling the volumes of the suspension and the weight of diluting water strictly, the homogeneity of the product (200 bottles) was satisfactory. An interlaboratory comparison test was performed by participants at 21 laboratories. In a statistical analysis, z-scores in a robust method were applied to reject outliers, and were followed by the usual statistical procedure. The certified value of this CRM in TEQ (Toxic equivalence quantity) is 46.5±1.9 pg L⁻¹.

The drift in sensitivity due to carbon deposition on the sampling cone, skimmer cone and ion lenses has been a serious problem in gas chromatography/inductively coupled plasma mass spectrometry (GC/ICP-MS). To overcome this problem, a high-speed switching method between a mixed-gas plasma and a pure-argon plasma (named plasma gas switching method) using an oxygen permeation tube and a switching valve was developed. This enabled both the cleaning of deposited carbon and enhancement of the sensitivity; as a consequence, both the repeatability and the sensitivity of polybrominated diphenylether (PBDE) were improved by more than 3 times and 4 times, respectively. The drifts of sensitivity over a period of 8 hours were less than 5％ in most cases. Concerning the analytical performance of thermally labile isomers from octa- to deca-BDE, the detection limits, dynamic ranges of the calibration graphs and unequivalent sensitivities were remarkably improved by using a metal capillary separation column coated with a very thin (0.05 μm) film of immobilized-polydimethylsiloxane. The detection limits ranged from 0.014 pg (BDE-154) to 0.093 pg (BDE-209), which were equal or superior to the lowest values reported hitherto by GC/MS (high resolution). A remarkable loss of sensitivity for highly brominated isomers, such as nona- and deca-BDE, was observed in the analysis of PBDE technical mixtures when the solvent was methanol. The loss of sensitivity turned out to be due to an activation of the retention gap used for on-column injection; this problem was solved by changing methanol to isooctane in the sample-preparation step before analysis.

A novel method for the determination of phenol at a carbon-paste electrode coated with over-oxidized polypyrrole and polyvinylpyrrolidone films (OPPy/PVP) has been developed. Phenol in a 0.1 M KCl solution was preconcentrated during an open circuit for 10 min, and was then determinated in a phosphate buffer (pH 10.0). A sensitive oxidation peak was observed at about .48 V (vs. Ag/AgCl). The peak current was well-proportional to the phenol concentration in a very wide range from 1.0×10⁻⁶ to 1.0×10⁻³ M, and the detection limit was 1.0×10⁻⁷ M. The modified electrode with high sensitivity and selectivity is easy to prepare, and can be applied to the determination of phenol in waste water.

A rapid capillary electrophoresis method was developed to detect perchlorate in tissues of male rats after the administration of perchlorate. Supernatants of ethanol-precipitated rat fluids were evaporated to dryness, and silver acetate solution was added. Precipitated silver chlorides were separated by centrifugation and supernatants were injected into a capillary electrophoresis system coupled with UV detection. The separation and quantification of perchlorate was achieved using Agilent inorganic anion buffer as the carrier electrolyte, electrokinetic injection and indirect detection at 200 nm. The lower detection limits for perchlorate in fluids and tissues of rats were 0.01 μg/ml and 0.25 mg/kg, respectively. Perchlorate in biological samples was determined for the first time by capillary electrophoresis already described.

A few decomposition methods were examined in order to determine impurities in sintered magnesia and spinel samples. Pulverized samples were severely contaminated by a grinding vessel. A lump (about 0.3 g) of sintered magnesia sample was decomposed with a mixture of 0.1 mL of hydrofluoric acid and 9.9 mL of hydrochloric acid in a Teflon pressure vessel at 170℃ for 4 h. Similarly, about 0.3 g of a sintered spinel sample was decomposed with 10 mL of sulfuric acid(1＋1) at 230℃ for 5 d, or with a mixture of 0.2 mL of hydrofluoric acid and 9.8 mL of sulfuric acid(1＋1) at 230℃ for 24 h. It was necessary to match the matrix components (acids, magnesium and aluminum) in standard solutions to those in sample solutions. The proposed methods were applied to several commercial samples, and the impurities were determined by ICP-OES. The detection limits of most elements (21 elements in magnesia, 20 elements in spinel) were below several μg g⁻¹.