Ts. Amartaivan

MICROBEAM ANALYSIS SYSTEM AT TOHOKU UNIVERSITY

A microbeam analysis system has been developed at Tohoku University for biological applications. Spatial resolution of less than 1 μm has been achieved with a beam current of ~40 pA. In microbeam analysis of biological specimens, simultaneous measurement of structural and elemental properties is very important. Our system is applicable to simultaneous in-air/vacuum PIXE, RBS and STIM analyses. Typical results of biological application are shown.

Microbeam Analysis at Tohoku University for Biological Studies

A microbeam analysis system at Tohoku University has been improved in detection efficiency for application to single cell analysis. The system is applicable to STIM analysis and to simultaneous PIXE and RBS analysis. Sample preparation methods suitable for non-adhesive single cell analysis were developed and first results with the improved analysis system are shown.

MICROBEAM ANALYSIS OF SINGLE AEROSOL PARTICLES AT TOHOKU UNIVERSITY

A microbeam system has been developed for the analysis of single aerosol particles. Combination of PIXE, RBS and off-axis STIM methods enabled simultaneous analysis for hydrogen to metal elements. Aerosol particles were collected on thin polycarbonate film (~0.3 μm) resulting in good signal-to-noise ratio. Quantitative elemental correlation was measured for single aerosol particles. A total of 270 particles were analyzed and clustered into 4 groups. The analysis system reveals the chemical composition of aerosol particles and is a powerful tool for source identification.

PIXE Analysis of Trace Heavy-Metals in River Waters Using an Ion-Exchange Cellulose Filter Paper

A simple but precise method for the PIXE analysis of trace heavy-metals in aqueous samples was developed, in which the PIXE targets were prepared by pre-concentrating heavy metals on a cellulose phosphate ion-exchange filter paper and no additional chemical treatment was required. Heavy metals in trace concentrations were quantitatively retained up to 16.7 μ-equivalent on a sheet of filter paper due to the excellent selectivity for heavy metals and ion-exchange kinetics of phosphate groups in cellulose matrix. Heavy metals of less than 1 μg on one filter paper are precisely and rapidly determined by PIXE analysis using 3-MeV proton beams. The present method is compared with the method preparing a PIXE target for each dissolved species of an element contained in aqueous samples. It will be resulted that the newly developed method enables an on-line PIXE analysis for river waters.

MULTI-SITE AEROSOL MONITORING USING MINI STEP SAMPLER

We developed mini step samplers with low manufacturing and running costs for application in multi-site air-pollution monitoring. The miniaturization of the sampler was achieved by reducing the suction nozzle size. We tested the samplers with suction nozzle diameters of 2 and 4 mm through simultaneous exposure in the same site. Elemental concentrations of aerosol collected by these samplers were consistent within ±20% during comparison and the sample uniformity did not differ significantly. Sampling with small suction nozzle did not adversely affect aerosol collection. Aerosol samples were collected simultaneously at two sites in our laboratory and in the hall outside for 3 days and analyzed subsequently by PIXE. The time variation of elemental concentrations was high during daytime and low at night time and also during the weekend. Elemental concentrations in the hall were always higher than those in the laboratory. In our laboratory, we change shoes at the entrance and therefore, elemental concentrations inside the lab are lower than in the hall. In a second field experiment, we carried out simultaneous multi-site aerosol sampling during two periods in correlation with meteorological data (wind direction and velocity). It was observed that elemental concentrations of some soil origin elements changed periodically. On the other hand, the concentration of Cu and Zn showed irregular concentration spikes whose pattern showed a variation with the sites. Analysis using the data of wind directions showed that Cu had been transported to the sites from northeasterly direction and that the concentration of Zn was influenced by two big factories nearby. In conclusion, it has been demonstrated that the multi-site sampling system combined with meteorological data is well suited to identify sources of pollution.

IN-AIR MICRO-PIXE ANALYSIS OF TISSUE SAMPLES

Micro-PIXE is capable of providing spatial distributions of elements in the micro-meter scale and its application to biology is useful to elucidate the cellular metabolism. Since, in this method, a sample target is usually irradiated with proton or α-particle beams in vacuum, beam heating results in evaporation of volatile elements and shrinking of the sample. In order to avoid these side effects, we previously developed a technique of in-air micro-PIXE analysis for samples of cultured cells. In addition to these, analysis of exposed tissue samples from living subjects is highly desirable in biological and medical research. Here, we describe a technique of in-air micro-PIXE analysis of such tissue samples. The target samples of exposed tissue slices from a Donryu rat, in which a tumor had been transplanted, were analyzed with proton micro-beams of 2.6 MeV. We report that the shape of cells and the distribution of volatile elements in the tissue sample remain uncharged when using a target preparation based on a freeze-drying method.

PIXE ANALYSIS OF TRACE HEAVY METALS IN RIVER AND TAP WATER USING AN ION-EXCHANGE CELLULOSE PHOSPHATE FILTER

An ion-exchange cellulose phosphate filter was used to prepare in-line PIXE targets for long-term monitoring of heavy metal concentrations in river and tap water. River water samples were taken every 30 minutes during 7 hours, and tap water samples every 5 hours during 150 hours. A PIXE target was prepared passing 300 ml of water sample and 2 ml of 20 ppm Y standard solution through a single sheet of the filter paper. Heavy metals (Mn, Fe, Cu, Zn, Pb and Hg) were detected by PIXE analysis with lower detection limits of 0.5-1.0 ppb. Analysis results show that the filter paper can trace concentration changes of heavy metals in a wide range.

BEAM DAMAGE OF CELLULAR SAMPLES IN IN-AIR MICRO PIXE ANALYSIS

The change of shape and elemental concentration of cellular samples in In-Air micro PIXE analysis was investigated. Cultured bovine aortic endothelial cells were analyzed in the atmosphere by using 2.6 MeV proton micro-beams. The shape of cross-sections of cells was not so much distorted by beam irradiation and the concentrations of trace elements did not change too, except for S. The concentration of S changed with strongly depending on the temperature rise due to beam irradiation.

PIXE ELEMENTAL ANALYSIS OF DRINKING WATER SUPPLIES

In this study, we carried out PIXE analysis of raw and treated water at five water treatment plants as well as of tap water from several houses located in each supply route. We used a simple fast procedure for preparing thin uniform targets of inorganic components in both soluble and insoluble fractions of aqueous samples in combination with preconcentration of trace heavy metals; that is, Nuclepore filtration targets for coarse particles, preconcentration targets for heavy metal ions and deposit targets for fine particles and soluble major constituents. The target preparation and the PIXE measurement are not time-consuming, and a broad range of concentrations (several tenths of ppb to a few tens of ppm) of 19 elements from Na to Pb is determined simultaneously with a precision sufficient to reveal the elemental distribution in the soluble and insoluble fractions. Tap water quality was examined as a function of elemental distribution in untreated water at the plants. We confirmed the increase of insoluble components of some heavy metals in untreated water taken from river due to heavy rainfall and the elution of Cu, Zn and Pb in drinking water by corrosion of the piping in some part of the water distribution systems.

MAPPING OF HEAVY METALS ACCUMULATED IN PLANTS USING A SUBMILLI-PIXE CAMERA

Phytoremediation is a technology for remediation of contaminated soils. In this study, we used a submilli-PIXE camera to analyze plants and soils from a shooting range. Some heavy metals were rapidly and easily detected in these samples. Element dot-maps of the plant show Cu and Pb accumulated in the epidermis of subterranean stems and the venation of leaves. From these findings, it is possible to map the distribution of heavy metals and to detail their location in the plant, using the submilli-PIXE camera. PIXE analysis is an effective tool for undertaking phytoremediation research.