The distribution of minor and trace elements in biological samples is very informative for bio-medical and environmental research.
Particle induced X-ray emission (PIXE) analysis is a powerful tool for this subject since it can analyze many elements in
samples non-destructively at high sensitivity and, with an advantage of micro-beam scanning capability. Recent studies in
Japan on the application of PIXE analysis to these fields are introduced in this paper.
In 2000, micro-beam scanning particle induced X-ray emission (PIXE) analysis system was installed in NIRS. This system provides
the ability of multi-elemental mapping on maximum 2.5 mm×2.5 mm area in a spatial resolution of about 1 μm with quadrupole
triplet magnets and a scanning coil. The estimated beam size on good tuning was 0.40×0.65 μm2, that is one of the best capacity of micro-beam scanning PIXE system in the world. The performance was tested using small
biological samples such as fish scale, pollen and small fish eye. Fine elemental maps were obtained in the samples of about
30 μm to a few mm size in the special resolution of about 1 μm.
In order to investigate the ingestion of iodine by human body and to know its content in organs, instrumental epithermal neutron activation analysis was used in conjunction with Compton suppression gamma-ray spectrometry by measuring the 128I short-lived nuclide. The interferences of 24Na and 38Cl induced from NaCl in a sample were reduced by factors of about 6 and 15 to 41 by employing the epithermal neutron activation and Compton suppression gamma-ray spectrometry, respectively. The present method can be used to determine iodine at levels higher than 11 ppb. It was applied to the determination of iodine of more than 35 ppb in various biological reference materials.
Authors:H. Aki, H. Ikeda, M. Yukawa, Y. Iwase, and N. Mibu
The complexation of β-lactam antibiotics, amoxicillin (AMPC), ampicillin (ABPC) and benzylpenicillin (PCG), with 2-hydroxypropyl-β-cyclodextrin
(HPCD) was studied at various pH values using microcalorimetry, 1H NMR spectroscopy, and molecular dynamic simulation. In the strong acid solution, two different types of inclusion complex
with a 1:1 stoichiometry, Complex I with a phenyl ring of β-lactam antibiotics penetrated into the cavity of HPCD and Complex
II with a penam included in the cavity, were formed by hydrophobic interaction, and Complex II was more stable than Complex
I. In aqueous solution at pH≥4.5, only Complex I was formed, where the penam of PCG was more deeply penetrated into the cavity
to keep it stable than those of AMPC and ABPC. The charged carboxyl-group on the penam was less affinity to form Complex II.
Authors:S. Homma-Takeda, Y. Nishimura, H. Iso, T. Ishikawa, H. Imaseki, and M. Yukawa
Microbeam analysis is used in biomedical and environmental sciences to determine the presence and concentration of trace elements.
However, quantitative analyses of biological samples are challenging because the chemical and physical compositions of existing
standards differ from those typically encountered in biological samples. We developed a thin standard using polyvinyl alcohol
and assessed its quality by microbeam scanning particle induced X-ray emission (micro-PIXE) analysis. The relationship between
metal concentration and X-ray intensity was linear for certain standards up to 500 μg·g−1. Using this new thin standard, micro-PIXE analysis of Zn content in samples of human hair agreed well with analysis performed
by inductively-coupled plasma mass spectrometry, validating the use of these new thin standards for quantitative mapping with
Authors:M. Yukawa, K. Aoki, H. Iso, K. Kodama, H. Imaseki, and Y. Ishikawa
The balance of essential elements in organisms can be changed by environmental stresses. A small fresh water fish, the medaka,
was irradiated with X-rays (total dose: 17 Gy, which is not a lethal dose for this fish). Essential elements in the liver,
gall bladder, kidney, spleen, heart and brain of the fish were measured by the particle induced X-ray emission (PIXE) method
and compared with those of a control fish. Various changes in the elemental balance shift were observed. The PIXE method can
analyze many elements in a small sample simultaneously, and so the changes in elemental content induced by irradiation were