BUNSEKI KAGAKU Abstracts

The dissolution of amorphous silica in aqueous solution in the presence of organic compounds was investigated as a preliminary experiment to elucidate the effect of organic compound on the Si concentration in soil solution. The organic compounds used in this study were Poly-N-vinylpyrrolidone (PNVP) and N-methyl-2-pyrrolidone (NMP) with carbonyl group that is a common functional groups of natural organic compounds. The dissolution rate and solubility of amorphous silica in each solution containing the organic compounds were investigated and compared with those of pure water under same condition. In PNVP solution, the dissolution of amorphous silica was retarded by covering PNVP adsorbed on silica surface. This fact may be due to stabilization by simultaneous and many hydrogen bonds between silanol groups on silica and carbonyl groups in PNVP. In contrast, in NMP solution, the solubility of amorphous silica increased compared with that in pure water, suggesting the formation of NMP-silicic acid complex. The DFT calculation showed that the stability energy of NMP–silicic acid complex was lager than that of silicic acid-water complex {Si(OH)₄ + NMP > Si(OH)₄ + H₂O} in gas phase, suggesting that NMP-silicic acid complex may be stabilized in aqueous solution.

Purified water is one of the most commonly utilized reagents in the laboratory. It is used throughout experimental protocols in virtually every type of laboratory application : as blanks, for the dissolution and dilution of samples, the dilution of standards, preparation of mobile phases and for media and buffer preparation. Contaminants present in purified water can therefore have a significant impact on results. Hence, it is important to ensure that the laboratory water-purification system contains a combination of purification technologies to target specific impurities related to each application. This article looks at some of these technologies and their relevance for specific applications, such as HPLC, LC/MS, and ion chromatography (IC).

Thermal behavior, structure and dynamics of water confined in mesoporous materials MCM-41 with various pore sizes have been investigated over a temperature range of 298 to 170 K by differential scanning calorimetry (DSC), FTIR, X-ray diffraction (XRD), quasielastic neutron scattering (QENS), and neutron spin echo (NSE) measurements. The DSC data showed that the smaller the pore size the lower the freezing and melting points. It has been found that water confined in pores of 20 Å diameter keeps the liquid state at temperatures down to 170 K. The X-ray radial distribution functions showed that the capillary-condensed water in the pores has more distorted tetrahedral structure than in bulk water with decreasing pore size. The QENS data showed that when the pore size decreases the translational diffusion of confined water is retarded to almost half compared with bulk water. The temperature dependence of the relaxation time of rotational diffusion and the residence time of translational diffusion of confined water showed the Arrhenius type behavior. The NSE data showed that the relaxation time of water confined in pores whose diameter is 20 Å follows the VTF equation above 220 K, whereas below 220 K they shows the Arrhenius type behavior, i.e. the dynamical crossover takes place in the confined water.

Understanding of the source and chemical characteristics of groundwater provides important strategies for the quality management of mineral water and food materials. To identify the source of groundwater used for food materials, water chemistry and stable isotopes of hydrogen and oxygen were examined in well-water from Sayama city, Japan. The well-water samples had similar chemical characteristics to river water in the west-rim of the Kanto plane. The hydrogen and oxygen isotopic ratios of the well-water samples indicated that their origin was solely meteoric, and that the groundwater mainly originated from upstream of the Iruma River (and other rivers) in the west-rim of the Kanto plane. A subsequent groundwater simulation produced down streamlines from the upstream areas of the Iruma River that correspond well with the groundwater flow estimated from the δD and δ¹⁸O values of the samples. Thus, the stable isotopes and water chemistry of the sampled water, groundwater flow simulation appears to be useful tools for tracing the origin of groundwater used for food materials.

Volatile sulfuric and nitrogenous compounds are well- known odor compounds derived from the breath. Recently, some short-chain fatty acids have been suggested to be related to oral malodor caused by certain oral diseases. Details of the mechanisms of oral malodor, however, have not been well understood, partly because of little content of such short-chain fatty acids in the breath and of the difficulty to collect sufficient amounts of them for analysis. To solve this problem, we have developed a new method, where the needle-type solid-phase micro-extraction technique and gas-chromatography mass spectrometry for collecting and for determining those fatty acids were utilized, respectively. As a result, isovaleric acid, butanoic acid and 2-methyl butanoic acid were detected in mouth air, and we determined the concentration of them under well-controlled conditions. The concentrations of isovaleric acid in saliva were also determined for a comparison, and found to be in accordance with those in the mouth air. (r = 0.4953, p < 0.0001). Therefore, such short-chain fatty acids in mouth air may originate from saliva. There was a correlation between the amount of the isovaleric acid and the strength of the oral malodor assessed by organoleptic tests (r = 0.3426, p < 0.001). Those results showed that the short-chain fatty acids could cause the oral malodor.

We developed a novel reversed-phase high-performance liquid chromatographic (RP-HPLC) method with a mobile phase containing an alkylammonium phosphate as an ion-pairing reagent for the simultaneous determination of iodide (I⁻) and iodothyronines {thyronine (T0), triiodothyronine (T3), reverse triiodothyronine (rT3) and thyroxine (T4)}. The iodo compounds were chromatographed on a Sunrise C18 column (150 × 4.6 mm I.D.) at a flow-rate of 1.0 mL min⁻¹ with UV detection at 225 nm and 10-μL injection. We investigated the influence of the mobile-phase parameters, which were the pH, the concentration of an ion-pairing reagent, the concentration of an organic modifier and the type of ion-pairing reagent, for the retention of iodo compounds. Good RP-HPLC separation of the iodo compounds was achieved using a mobile phase of 5 mM tributylammonium phosphate (pH 3.0)-acetonitrile (64 : 36, v/v). The calibration curves for I⁻, T0, T3, rT3 and T4 were linear over concentration ranges of 5.0 × 10⁻⁷−5.0 × 10⁻⁴, 2.5 × 10⁻⁷−2.5 × 10⁻⁴, 2.0 × 10⁻⁷−2.0 × 10⁻⁴, 2.0 × 10⁻⁷−2.0 × 10⁻⁴ and 2.0 × 10⁻⁷−2.0 × 10⁻⁴ M, respectively. The detection limits (S/N = 3) for I⁻, T0. T3, rT3 and T4 were 2.6 × 10⁻⁸, 4.0 × 10⁻⁸, 1.2 × 10⁻⁸, 1.4 × 10⁻⁸ and 1.3 × 10⁻⁸ M, respectively. We applied this method for the simultaneous determination of I⁻ and iodothyronines in commercial thyroid tablets.

A simple and rapid analytical method using hydrophilic interaction liquid chromatograph-tandem mass spectrometer method was developed for the determination of six non-volatile amines in beer. As a result of validation tests, the linearity of the standard curves was sufficient in the range from 0.5 mg/L to 500 mg/L (r > 0.999). The recoveries were also between 73 and 122% for each analyte. These results permitted us to determine the non-volatile amines in beer. Then the analytical method developed was applied to survey the amount of non-volatile amines in Japanese domestic beer, happoushu, shin-genre, beer-taste drink and imported beer. The results indicated that the quantities of non-volatile amines in these products were lower than toxic levels, and suggested that there were no significant health concerns for ordinary persons.

The values of multiple correlation coefficients and coefficient determinations are obtained by multiple-regression analysis. The values of the multiple-correlation coefficient and coefficient determination show the extent of the variation in measured values. A known sample to more than 0.999 value of the multiple-correlation coefficient and coefficient determination was used for quantitative analysis. An inadequate unknown sample for accurate quantitative analysis was determined from the values of multiple correlation coefficients and coefficient determinations. When the multiple-correlation coefficient and coefficient determination were less than 0.99900, the unknown samples were un-suitable for the quantitative analytical results. At this time, the determinations of inadequate samples for accurate quantitative analysis using 13 measured values by GC-MS were performed by this method.

An individual determination of the structurally analogous polybrominated flame retardants by using the derivative spectrum chromatogram method with an HPLC-diode array detector was investigated. These flame retardants have a high boiling point, and could be hardly analyzed by HPLC-MS/MS and GC-MS. Two octabromodiphenyl ethers (octa BDEs) related congeners, BDE-204 and BDE-205 showed almost the same UV-spectrum and elution behaviors in RP-HPLC. Even for such similar properties, the derivative spectrum chromatogram method allowed a selective determination of the congeners. This method was applied to the polyester resin kneaded octabromodiphenyl ether (technical) to evaluate its qualitative and quantitative properties. The ratio chromatograms of the multi derivative spectrum were effective to confirm the peak purity.

For the determination of trace-level elements in metallic samples, several chemical procedures for the separation and pre-concentration from the matrix metals have been employed. However, troublesome problems are frequently encountered in the chemical separation procedure. Especially, the analytical values may contain errors due to contamination of the analyte from several experimental situations ; this phenomenon results in an increase and the variance in a blank value in analysis. For decreasing the blank value, it is necessary to evaluate the cause for contamination through the analytical procedure. The authors investigated the effects of contaminants attributed to the experimental tools, reagents and an environment on the blank value for the trace analysis of silicon in metallic samples in molybdosilicate blue spectrophotometry after silicon tetrafluoride separation. For analyzing trace silicon with better precision, the experimental instruments have to be cleaned and reagents containing the lowest concentration of silicon have to be selected and employed. Moreover, the analytical operations should be carried out in a short time and amounts of the reagents should be reduced as much as possible.

Winter rain, fresh snow, rime and glaze samples were collected on the top of Mt. Kajigamori (ALT. 1400 m), which is the watershed protection forest of Riv. Yoshinogawa with an altitude of 1400 m, Kochi, Shikoku Island in West Japan during the winter season of 2010 (December 2009 and March 2010). Lead and cadmium in the rain, snow, rime and glaze were analyzed by graphite furnace atomic absorption spectrometry together with the ionic components (Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, F⁻, Cl⁻, NO₂⁻, Br⁻, NO₃⁻, PO₄³⁻, SO₄²⁻) by ion chromatography, and pH, E.C. during the winter season. In the back-trajectory over Russia-Japan Sea, very low concentrations of Pb and Cd were observed in all samples. From the back-trajectory over North China and Korea, it was considered that the observed relatively high concentration of Pb in snow and rime and Cd in rain showed a possibility of long-range transportation from the East Asis region. The low concentration of lead in rime ice and fresh snow collected at Mt. Tateeboshiyama (ALT. 1299 m) in Shobara city, Hiroshima (Mt. Hibasan quasi-national park) was observed with back-trajectry over Russia-Japan Sea.