Vol. 59 No. 11
Water is a typical diamagnetic liquid, but the property has rarely been utilized in analytical method. However, the magnetic force is sufficiently strong to migrate micro-organic particles in water and vice versa, if the magnetic field and its gradient are properly designed on the micrometer scale. The magnetic susceptibility has additivity on those of the components, and can thus be used, for example, to determine paramagnetic ion in an organic droplet in water as smaller as 10−18 mol, and the interfacial concentration on the order of 10−10 mol cm−2 on a microdroplet in water. The magnetophoretic trapping force can be used for the size separation of microparticles in aqueous solution. On the other hand, the Faraday effect, which is a typical magneto-optical effect, reflects the diamagnetic property of water and the σ-bonding property of water molecules. Faraday imaging, observed by an optical microscope under the application of a pulsed magnetic field, can recognize the magnetic property and the π-electron property of liquid components. The Faraday rotation angle also shows additivity on those of the components. On a series of lanthanide(III) ions with a different number of 4f electrons, the regularity between the observed effective Faraday transition probability and the magnetic moment has been understood. In this article, promising potentials of magnetophoresis and Faraday rotation measurement as new micro-analytical methods are described.
The water quality of the Seto Inland Sea has recently improved compared with that in the 1970s and early 1980s, but the fisheries yield of species such as sardine and short-neck clam has decreased. Since 2002, the Nori (Porphyra) culture has been particularly heavily damaged due to a lack of nutrients. In this paper, we review our previous water quality results of the Seto Inland Sea, which focused on the Nori culture directly influenced by the nutrient concentrations. Moreover, we discuss the potential mechanism for low levels of dissolved inorganic nitrogen (DIN) concentrations and poor Nori production. Our results suggest that the reasons for the recent decreases in nutrient concentrations are (1) decrease of nutrient loading from riverine sources, (2) an increase of nutrient uptake by phytoplankton growth due to an increase of euphotic depth, (3) the diffusion of nutrients in the bottom marine layer due to a decrease in stratification, and (4) a decrease of the upward nutrient flux across the overlying water-sediment interface.
Surface force measurements represent a powerful tool for the molecular-level characterization of water at solid-liquid interfaces, which is important for various functionalized interfaces, including biointerfaces. We have studied the properties of interfacial water using surface force measurements and resonance shear measurements, which we developed. This paper summarizes some of our recent research : (1) water confined between mica surfaces and (2) the molecular macrocluster formation of water adsorbed on silica surfaces.
To clarify the spatial and temporal variations and the chemodynamics of persistent organic pollutants in seawater on a global scale, we developed monitoring systems and installed them in merchant vessels as voluntary observation ships. We also observed persistent organic pollutants in seawater in the Pacific Ocean and the South China Sea. We used a balk carrier between Japan and Australia, a cruse vessel on the South Pacific Ocean and Antarctic Ocean, and a container ship between East Asia and North America as voluntary observation ships. For sampling persistent organic pollutants, we used a solid-phase extraction method, and 100 L of seawater was passed through columns containing solid-phase extractors, and immediately the sample was stored on the vessel at −20°C. The sample was stored in a freezer at the National Institute for Environment Studies, and analyzed by the HRGC/HRMS-SIM method. We detected persistent organic pollutants in all samples, and their concentrations and contents of isomer were very characteristic. These data give much information for analyzing the emission source and the transporting route.
The continuous development of the soft ionization technique is thought to have sparked the advancement of mass spectrometry (MS). Cold-spray ionization (CSI) has been adapted for analyses of various unstable organometallic complexes and biomolecules in solution. A combination of unique analytical capabilities, including CSI-MS, NMR and XRD has been developed to provide new insights about molecular interactions. CSI is designed for the mass spectrometric detection of labile organic species. It may be an appropriate method to analyze in solution the structure of bimolecular complexes, labile organic species including Grignard reagents, asymmetric catalysts, and supramolecules in solution. The method, a variant of ESI-MS, operating under low temperature, allows for a simple and precise characterization of labile noncovalent complexes that are difficult, or impossible, to observe by conventional ionization techniques. The principle of the CSI method and applications of the method in conjunction with other analytical techniques to a wide variety of labile organic species such, as molecular clusters, supramolecular polymers and host-guest complexes in solution, are presented. A new ionization method that uses metal-complex-based ionization probes to ionize large complex molecules, including biomacromolecules, are also shown.
A method for determining strontium and lead isotope ratios of grains was developed. The samples investigated in this study were rice, barley and wheat. The samples were digested with nitric acid and hydrogen peroxide, and heated in a heating block. Strontium and lead were separated from the matrix by adding an acid digested solution into a column packed with Sr resin, which has selectivity for the absorption of strontium and lead. Strontium and lead isotope ratios were determined using a high-resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) with a single collector. The intraday relative standard deviations of 87Sr/86Sr and lead isotope ratios (204Pb/206Pb, 207Pb/206Pb, 208Pb/206Pb) by HR-ICP-MS measurements were < 0.06% and around 0.1%, respectively. This method enabled us to determine strontium and lead isotope ratios in two days.
Pyrolysis-gas chromatography (PyGC) was used for cured novolac resins with hexamethylenetetramine (HMTA) in order to investigate the cross-linked structure. Several kinds of novolac fractions having various molecular weights and ortho ratios of methylene linkage (OR) were pyrolyzed at 670°C. Phenol and methylphenols which were pyrolysis products were determined quantitatively using a gas chromatograph. There was a correlation between the composition of pyrolysis products and the structure of resin and the formulae to estimate OR and M/P from PyGC data were obtained. Based on PyGC analyses of cured high-ortho novolac or random novolac resins with HMTA by using the obtained formulae, it was shown that random novolac efficiently reacted with HMTA than high-ortho novolac.
COD (chemical oxygen demand) is one of the most popular methods for evaluating organic pollutants. In the present paper, a chemiluminescence detection method for measuring the concentration of permanganate ion after reacting with organic compounds is described ; the chemiluminescence occurs based on the direct reaction between permanganate and luminol. In order to use this system, a buffer solution, the concentrations of permanganate and luminol were inspected. Fifty μM of MnO4− was reacted with the sample, and then the chemiluminescence was detected with a mixture solution (250 mL of 1.5 mM luminol, 250 mL of 0.01 M 1,10-phenanthroline, and 500 mL of 1 M ammonium sulfate at pH 9.6 (adjusted with 25% ammonium solution). Also, a method for reducing the COD was proposed : where the sample solution flows a 100 m length PFA (perfluoroalkoxy-fluororesin) microtube (i.d. = 0.2 mm and o.d. = 0.4 mm). The PFA tube was wound around the outside of a quartz tube (o.d. = 30 mm, length = 120 mm). Two low-pressure mercury lamps (5 μW at 1 m distance) were inserted into the quartz tube. It could be calculated that about 45% of 254 nm radiation of the lamp reached the inside the PFA microtube. When this photo-decomposition system is applied, 0 to 90% of COD can be reduced. A total flow system for the photo-decomposition-chemiluminescence detection system for COD was constructed.
A visual spot test has been developed to make it possible to discriminate between different types of fine paper using Bromochlorophenol Blue (BCPB)-hydrochloric acid solutions. When a drop of the solution is dropped onto a piece of paper, the solution retains a semispherical shape or spreads through the capillaries depending on the water repellency of the paper, and depending the on paper composition, either a yellow or blue stain appears. When six BCPB solutions with different concentrations of hydrochloric acid in the range of 0.01〜0.6 N were separately applied to eight kinds of paper, they were able to be classified into six groups according to differences in their water repellency and the color change of BCPB upon drying. Furthermore, the eight kinds of paper that had been printed using an inkjet printer were also able to be classified into five different groups, despite a loss of water repellency due to printing. There was good agreement between the color change of BCPB on the paper and the amount of calcium carbonate filler in the paper. Our visual method serves as a first-stage screening test for the discrimination of paper without any special equipment, and will be useful in practical forensic examinations.
Stripping voltammetry using a boron-doped diamond (BDD)-electrode is described for the determination of uranium. A uranium solution adjusted to pH 3 was supplied to the surface of an electrode continuously by a carrier solution at 0.10 mL min−1, and uranium in the solution was accumulated. An accumulation potential of −2.5 V (vs. Ag/AgCl) was applied to the BDD-electrode. After the accumulation step, the flow of the carrier solution was stopped and the stripping voltammogram, ranging from −2.5 V to 1.0 V (vs. Ag/AgCl), was recorded. A linear relationship between the stripping peak current and the uranium concentration existed in the range from 0 to 1270 ng mL−1, and the relative standard deviation of five repeated analyses was approximately 5% for 0.50 mL of an uranium standard solution of 127 ng mL−1. The method was applied to the determination of uranium in low active liquid wastes from a spent nuclear-fuel reprocessing plant.
Printer identification based on nondestructive analysis has many desirable forensic applications, for example counterfeit currency and documents. In the present work we investigated the residual solvents with pigment ink on printings by gas chromatograph mass spectrometer (GCMS) after methanol extraction without any destruction. Seven compounds were identified by GCMS using standard chemicals. We proposed that trimethylolpropane (TMP) is an important compound to discriminate four printers. Two of them have TMP, and the others do not. After extracting yellow pigment with dichloromethane, magenta points were measured by a microscope-spectrometer. First-order derivative spectra from four printings were also divided into two groups. One group had the maximum absorbance wavelength at 510 nm and 545 nm, and the other one was at 520 nm and 555 nm. Four inkjet color printers produced by EPSON were clearly discriminated by GCMS and microscope-spectrometer.
An estimation of the chemical composition of cement in hardened concrete by an electron probe microanalyzer was studied. Concretes were prepared with ordinary Portland cement (OPC) and blast furnace slag cement (BSC). Two square areas of 400 micrometers by 400 micrometers in the concrete were subjected to mapping analysis to quantify nine major elements of cement. The size of a pixel for analysis was fixed at 1 micrometer by 1 micrometer. Quantified values of the elements (as oxide) in each pixel were converted by treating their sum as 97% or 98% and retaining their relative ratios. The average of the converted composition for many pixels was caluculated, and it was regarded as being the estimated composition of cement. The average for all 160000 pixels was higher in SiO2 and Al2O3 and lower in CaO than the actual chemical composition of cement. Aggregates were considered to be the reason for high SiO2 and Al2O3 and low CaO in the estimated composition. It was clarified that the exclusion of pixels corresponding to aggregates was important for a proper estimation. The exclusion of pixels corresponding to aggregates based on the values of SiO2 and CaO made it possible to obtain the estimated composition close to the actual one. An estimation of a concrete collected from an actual structure clarified that the chemical change in the cement paste, such as carbonation or solution of CaO, lowered the accuracy of the estimation. Areas at which such a change proceeded should be determined by mapping analysis for a wide area, and they should not be selected as the area for an estimation.
We developed a new staining method for the distribution of peroxidase (POD), which is a coloration caused by the reaction between luminol and hydrogen peroxide in the presence of POD. Using this method, the hydrogen peroxide revelation promoted the extension of bud and the induction of peroxidase on the germination of brown rice. From the above result, this method has been determined to be a useful technique for studing its role for POD in plants.
A flow injection system for simultaneous determination of phosphate and silicate ions based on the formation of molybdenum blue is developed. This system is based on the difference of sulfuric acid concentration between phosphate and silicate on the formation of molybdenum blue. In this system, a part of sample zone in carrier is mixed with sulfuric acid solution and then, high and low concentrations of sulfuric acid zones are formed in the sample zone. In the low concentration zone, phosphomolybdenum, silicomolybdenum and isopolymolybdenum blues are formed. In the high concentration zone, only phosphomolybdenum blue is formed. Phosphate and silicate ions are determined by the difference of absorbance (830 nm) between high and low concentration zones. The determination limit of phosphate ion estimated was 0.003 mg L−1 as P and that of silicate ion was 0.04 mg L−1 as Si. The analysis rate was 6 samples h−1. This system was available for phosphate and silicate ions in the sea water.
Analytical methods for various organic compounds using a smaller number of reference materials were developed. Two reactors were connected between the separation column of the gas chromatograph (GC) and a flame ionization detector (FID) to prepare a post-column reaction GC-FID system. In this system, analytes were separated, transformed, first to carbon dioxide, then to methane, and finally detected as methane. Hydrocarbons and oxygen-containing organic compounds, such as alcohols, ethers, esters, and ketones, were selected as the target compounds. It was shown that they were all converted to methane quantitatively, and gave the same sensitivity. Thus, their precise quantitative analyses were able to be performed by the developed method using one reference material. The relative standard uncertainties of the analytical values were below 1%. The developed method was validated using SI-traceable reference materials. Statistical inspections of the obtained results were carried out using the En number, and showed satisfactory performance. By applying the developed method to evaluate reference materials, the number of necessary primary and/or secondary standards for calibration will be decreased.