BUNSEKI KAGAKU Abstracts

Humic substances (HSs) are naturally occurring surface-active materials that have an amphiphilic nature for both hydrophilic and hydrophobic properties. Such functions of HSs do not serve as only sorption of hydrophobic organic pollutants (HOPs), such as polycyclic aromatic hydrocarbons, polychlorinated dibenzo-p-dioxins and pesticides to soil particles, but also as solubilization that leads to the movement and diffusion of HOPs. These antithetic properties of HSs have been attempted to apply to remediation techniques for contaminated soils and groundwater. Such unique characters of HSs for HOPs can be attributed to the fact that HSs are known to be heterogeneous materials in which the structural features are varied by the conditions of their genesis. However, the heterogeneity of HSs can yield difficulties in estimating how HSs are effective when these are applied to contaminated sites. In this paper, we review previous studies concerning the functions of HSs with respect to the interaction with HOPs ; also prospects for applying the HS functions to soil remediation are discussed.

During the process for the bioleaching of sulfides, the surface of the target mineral is sometimes covered with intermediates, and the final products that interfere with the extraction of the target metal. Understanding the characterization and formation order of the secondary minerals responsible for passivation is a key to resolving the passivation mechanism. The present article reviews identification of secondary minerals and intermediates in a process of bioleaching of several sulfides by X-ray photoelectron spectroscopy, Raman spectroscopy, identification of the jarosite group minerals using Raman spectroscopy, and expectation of the formation order of the secondary minerals by SEM-EDX and TEM. The TEM observation in a nano-domain provides useful information about amorphous the secondary minerals. A passivation model was proposed to keep maximizing Cu recovery and minimizing As solubilization for the bioleaching of arsenic-bearing copper sulfides using super-thermophilic archaea, which are expected to be new target minerals in the near future.

Mineral resources are indispensable to human beings, as well as modern civilization and technology. Thus, our current lifestyles depend on a stable supply of mineral resources. This paper reports several isotopic studies on the genesis of mineral deposits to assist mineral exploration. Following a basic description of hydrothermal ore deposits and light-element isotopes, several studies on hydrothermal ore deposits are reported. These deposits include a skarn-type ore deposit (the Kamioka deposit), hypothermal ore deposits (the Ohtani and Kaneuchi deposits) and epithermal ore deposits (the Noya and Kushikino deposits). Secondary ion mass spectrometry (SIMS) for the microanalysis of microscopic textures of minerals from ore deposits is further described. Some SIMS applications other than for ore deposits are also mentioned.

Poly(N-isopropylacrylamide), PNIPAAm, is quite soluble in water and alcohol, but insoluble in certain mixtures of them. This property, called co-nonsolvency, was applied to the extraction of oils from ethanol eluate and turbidimetric detection. Oils were eluted with a PNIPAAm – ethanol solution by passing through the soil sample. Subsequently the oils were extracted into a dispersed polymer phase, forming from the eluate with the addition of an aqueous NaCl solution. The polymer phase adherent on the wall of a polypropylene bottle was separated from the liquid phase, and dissolved into freshly added water. The oils in the polymer phase were deflocculated as an emulsion particulate in the water. The turbidity of the emulsion was dependent on amounts of the oils. A column-type eluting apparatus equipped with a filter, a bottle for the reaction, and a portable photometer were proposed as a kit for on-site analysis. Oils at 400 – 5000 mg kg⁻¹ in 1.0 g of soil could be determined within about 10 min of the entire procedure. The results from simulated polluted samples were successfully related linearly to the value of the total petroleum hydrocarbon (TPH) measured by GC. The proposed method is a useful screening tool for judging soil pollution with mineral oil.

Isotope ratio analysis for ²³⁵U and ²³⁸U in soil samples using a microwave digestion procedure associated with ICP-MS was proposed and demonstrated. In the microwave digestion procedure, the dissolution of natural uranium in silicate (in rocks) was reduced by using a mixture of nitric acid and hydrogen peroxide (to measure the radioactive uranium from a disaster). Upon ICP-MS, the isotope ratio of the certificated geochemical reference material was realized to precisely correct the isotope ratio in real soil samples. In addition, cell-pass voltages can be available to make calibrations and/or to correct the mass bias in the mass-spectrometer. By these effects, the isotope ration of uranium can be measured with an accuracy of 0.37% without using a radioactive standard source. ²³⁵U and ²³⁸U were quantitatively determined, and those detection limits were both 0.010 μg/kg. In the case of an emergency, like a nuclear hazard, the proposed method is useful to immediately gather a large amount of information in large area as compared with a common method such as a complete dissolution process associated with an α-ray spectrometer or ICP-MS. In addition, the survey of how radioactive uranium spreads was conducted from 7 to 80 km around the Fukushima Daiichi Nuclear Power Plant (Fukushima-DNPP) (115 points in Fukushima prefecture). As a result, the values of the uranium isotope ratio for those soils were similar to the natural abundance, although the various concentrations of uranium were detected from sampling points.

New anion-exchange di-cation type stationary phases D₆C_m (m＝1, 6, 10, 14) having two quaternary nitrogen atoms were synthesized in two steps : first from the reaction of chloromethylated styrene-divinylbenzene copolymer and N,N,N',N'-tetramethyl-1,6-diaminohexane to give monocation-type stationary phase, D₆, with a quaternary nitrogen atom ; then by the reaction of D₆ with alkyl methanesulfonates having different alkyl chain lengths. The ion-exchange capacities of D₆ and D₆C_m were determined by Mohr method. The separation of all aldopentoses was successfully performed on the new stationary phases, D₆C_m, using 0.1 M NaOH eluent.

To obtain a performance evaluation method that is required in the simultaneous analysis of semi-volatile organic compounds using a gas chromatograph – quadrupole mass spectrometer (GC-QMS) and an automated identification and quantification system with a database, a set of performance check standards, which can monitor the transition of GC-QMS’s conditions caused by measurements of real samples, have been developed. First, food samples were injected into GC-QMS 160 times as a matrix source ; then the exchange of an injection port liner, cutting off of both edges of capillary column, cleaning and replacement of the ion-source parts have been carried out one by one. During these operations, a solution of 220 kinds of candidate compounds was measured 29 times to obtain the changes of the detected amounts and shifts of the retention times. As a result, the detected amounts of 115 compounds had changed to less than 80% or over than 120% of those in the first analysis ; the retention times of 5 compounds shifted by more than 6 s through a matrix load test. In addition, the detected amounts of 77 compounds decreased to less than 70% of those in the first analysis through the ion-source maintenance operation. From these results, 19 compounds were proposed as a set of suitable compounds for performance check standards to monitor the inertness of the injection port, capillary column and ion-source parts, shifts of the retention times, and drifts of mass spectrometry tuning.

Since the separation and concentration of fluorescent sample molecules occur simultaneously in capillary isoelectric focusing (cIEF) with laser-induced fluorescence (LIF) detection (cIEF-LIF), this is an effective technique for a highly sensitive analysis method. However, with the conventional cIEF-LIF, in which the fluorescent sample molecules are separated on the basis of differences in their isoelectric points (pIs), the application of this technique was limited in the case of poor differences of their pIs. Combining the molecular mass measurement of separated fluorescent sample molecules with cIEF-LIF is expected to overcome this problem. To confirm this possibility, we have developed the new system that combines microchip isoelectric focusing with laser-induced fluorescence detection (mIEF-LIF) and fluorescence correlation spectroscopy (FCS). FCS provides the average number of fluorescent molecules and the diffusion constant, which reflects their molecular mass in the detection field. The developed system consisted of three kinds of technical elements : microchip-based mIEF, scanning LIF detection and FCS measurement. Two kinds of fluorescent sample molecules (tetrametylrhodamine labeled peptide and protein) were focused in the channel by isoelectric focusing ; the channel was scanned by using the principle of Laser Scanning Microscopes, and a FCS measurement was performed at a focused zone of fluorescent sample molecules in the channel. Consequently, we found that the developed system was 20-times more sensitive than before focusing, and the molecular weight was estimated by the measured diffusion time in the microchip with a pH gradient. The mIEF-FCS, which combines separation analysis by mIEF-LIF and FCS, is expected to be a new analysis system.