BUNSEKI KAGAKU Abstracts

Aerosol water droplets play important roles in Earth's climate and atmospheric chemistry. Non-contact levitation of single micrometer-sized water droplets in air can be achieved by a laser trapping technique, and is therefore a powerful means to study the aerosol chemistry. In the present work, an in situ characterization of the chemical composition and size of an aerosol water droplet was demonstrated by means of laser trapping and Raman spectroscopy. Furthermore, the laser trapping technique has been applied to direct observations of the freezing processes of single micrometer-sized water droplets in air. An artificial experimental model system corresponding to the initial steps of precipitation in clouds can be constructed by employing this technique and an optical microscope.

There are many chemical species in the atmosphere, and it is difficult to measure all of them for air-quality monitoring. Therefore, the total OH reactivity had been proposed as an indicator of air quality. The total OH reactivity can be directly measured by employing a developed system using lasers. However, this system is complicated to operate, and expensive, because it requires 3 lasers. Here, a new lower-cost and user-friendly OH reactivity measurement system using a comparative reactivity method (kind of competitive reaction method) has been developed. In this OH reactivity measurement system, a comparative reactivity substance is added to the air sample, and then the OH radical is mixed. From a decrease of the comparative reactivity substance, the total OH reactivity of the sampled air can be deduced. The decrease in the comparative reactivity substance is monitored by proton transfer reaction mass spectrometry or GC-FID. These OH reactivity measurement systems using the comparative reactivity method have been tested for ambient air measurements and were compared with the OH reactivity measurement system using lasers.

A non-target analytical method for environmental contaminants by LC/Q-ToFMS/MS is presented. The elemental compositions of ionized intact molecules, product ions and corresponding neutral losses for 112 chemicals of environmental interest were elucidated to analyze those fragmentations in MS/MS. After analyzing the fragmentations of the chemicals, all of the ions and the neutral losses (i.e. 232 of the precursor ions, 400 of the product ions and 172 of the neutral losses) were registered in a provisional database for fragmentation analysis in accordance with the relationships. A mass spectrum of Bendiocarb measured by LC/ToFMS was used for two kinds of fragmentation analyses followed by structural identifications with the method presented here and the “Met Frag”. Two kinds of pesticide including Bendiocarb were identified by the presented method. On the other hand, based on “Met Frag”, Bendiocarb was the 27th place of the similarity in the mass spectra of 1754 structures found in “Chem Spider”. The identification algorithms were different between the two. The method presented analyzes fragmentations of mass spectra, and reports possible substrates corresponding to ions and neutral losses without comparing mass patterns. This means that the method may detect possible substrates, even if no ion of the same mass number as that of the ionized intact molecule was found in the database. The provisional database of MS/MS fragmentation is too small to use for non-target analysis. Further study is necessary to develop a non-target method widely applicable and easy to use.

Our group has reported on a specific microfluidic behavior of solvents, i.e., the tube radial distribution of mixed solvents in a microspace. We in short call it the “tube radial distribution phenomenon” (TRDP). For example, when a ternary mixed homogeneous solution of water–hydrophilic/hydrophobic organic solvents is delivered into a microspace, such as a microchannel or a capillary tube, the solvent molecules are radially distributed in this microspace, generating inner and outer phases. The TRDP was examined through fluorescence photographs, the construction of a phase diagram, and the elution behavior of solutes in a capillary tube. The TRDP creates a kinetic liquid-liquid interface in a microspace. A capillary chromatography system where the outer phase functions as a pseudo-stationary phase under laminar-flow conditions has also been developed based on the TRDP. This is called “tube radial distribution chromatography” (TRDC). Otherwise, we have investigated the extraction, mixing procedure, and chemical reaction based on the TRDP. They are called “tube radial distribution extraction” (TRDE), “tube radial distribution mixing” (TRDM), and “tube radial distribution reaction” (TRDR), respectively. The concepts and experimental data regarding TRDP, TRDC, TRDE, TRDM, and TRDR are described in this manuscript.

Recent developments of Raman optical activity (ROA) spectroscopy enabled detailed structural analysis of backbone structures of proteins in solutions. ROA can be used as a powerful analytical technique for determining protein secondary structures of protein amyloid fibril and its naturing intermediates where NMR spectroscopy is difficult to be applied.

The determination of carbon monoxide hemoglobin (CO-Hb%) in blood by different calculation methods involving regression analysis (DCR) and principal component score (PCA) was carried out using 0% and 100% of CO-Hb% in blood. However, both hemoglobin and carbon monoxide hemoglobin in blood are degenerated by heat or putrefaction. As a result, the correct CO-Hb% in blood is not obtained, and any judgment of the cause of death may be mistaken. Thus, the degree of degeneration of blood was examined based on regression statistics (R2), the sum of the coefficient in the multiple-regression equation, and the sum of the third principal component score. As a result of degenerations, the values of R2 and the sum of the coefficients in multiple regression equation decreased, and the sum of the third principal-component score is increased. Consequently, the presumption of the degree of degeneration in blood was attained from the change of these values. Also, a check of the cause of degeneration was attained from the third principal-component residual spectrum of the sample blood. Furthermore, the correct CO-Hb% in the sample blood was calculated from the determination value of CO-Hb% and the absorbance of the third principal component of 533 or 570 nm.

An analytical method for the determination of Diphenylarsinic acid (DPAA), Phenylarsonic acid (PAA) and Phenylmethylarsinic acid (PMAA) in groundwater by liquid chromatography mass spectrometry (LC/MS) has been developed. The phenylarsenic compounds were separated by LC with an anion-exchange column, and identified by electrospray ionization mass spectrometry using the m/z 261, 201, and 199 as monitoring ions for DPAA, PAA and PMAA, respectively. Quantitative measurements were performed by the internal-standard method with isotope-labeled phenylarsenic compounds as internal-standard compounds, in which quantification was not influenced by the matrix effect. The instrument quantification limits by this analytical method were 0.77 μg L⁻¹, 0.48 μg L⁻¹ and 0.30 μg L⁻¹ for DPAA, PAA and PMAA, respectively. We found monitored phenylarsenic compounds in groundwater by this method for two years. The occupancy of each phenylarsenic compound to the total arsenic concentration was 85% (DPAA), 11% (PAA) and less than 1% (PMAA), respectively, until the earthquake that occurred on 11th Mar 2011, but that varied after the earthquake. The cause was presumed to be due to the exchange of the pumping wells.

Lung cancer is a leading cause of cancer-related deaths. Hence, developing early stage diagnostic tests that are highly sensitive and specific is crucial. In order to achieve a desirable preventive medicine in the future, a non-invasive diagnostic technique with a volatile biomarker is a key. In this work, we compared VOCs obtained from the urine of tumor-bearing mice and normal control mice, and found 21 VOCs to be candidate biomarkers for lung cancer. To more efficiently extract the candidate biomarkers, we tested five different pretreatment methods. Among these the most improved extraction efficiency was the addition of sodium chloride along with a heat treatment.

Metal ions play an important function related to nutrition. On the other hand, they aid in the manifestation of toxicity, and induce symptoms of systemic toxicity. Since the various roles of metal ions are not clear in many cases, high sensitivity, high selectivity, and a simple determination of metal ions are needed. Spectrophotometry was a target for three metal ions (iron, titanium, and cobalt) and a metal–related substance (ascorbic acid). Each measurement range obeyed Beer’s law with an effective molar absorptivity of 20 – 670 ng mL⁻¹, 1.3 × 10⁵ L mol⁻¹ cm⁻¹ for iron; 24 – 340 ng mL⁻¹, 2.24 × 10⁵ L mol⁻¹ cm⁻¹ for titanium; 20 – 470 ng mL⁻¹, 1.35 × 10⁵ L mol⁻¹ cm⁻¹ for cobalt; and 20 – 120 ng mL⁻¹, 2.1 × 10⁶ L mol⁻¹ cm⁻¹ for ascorbic acid. Their sensitivities were higher than those of conventional methods, and good reproducibility was achieved. Spectrofluorometry was a target for one metal ion (aluminum). The measurement range of this method was found to be 0.03 – 1.50 ng mL⁻¹, which is over 10-times higher than that for spectrophotometry measurements. In addition, we considered the composition of colored complexes, performed characterizations, and analyzed the crystal structures of xanthene dyes.