ELECTRON-ENERGY-LOSS SPECTROSCOPY (EELS) OF IODINE IN THYROXINE - PARAMETERS OF RADIATION-INDUCED LOSS OF IODINE

The loss of iodine during irradiation with electrons was measured in o rder to determine whether it can be detected by electron spectroscopic imaging (ESI). Since iodine can be bound to organic molecules, it cou ld be a candidate for tracer studies by ESI in biomedical research. A solution of thyroxine spread over a carbon film was used as a test spe cimen. Thyroxine contains four iodine atoms covalently bound to aromat ic rings. For ESI, higher doses have to be used than in conventional e lectron microscopy. The iodine content was therefore measured after ir radiation with doses of up to 3 x 10(7) el nm(-2). The measurements we re carried out for different specimen thicknesses, temperatures and do se rates, and it was found that iodine can be detected with ESI if mod erate dose rates are used at a temperature of -160 degrees C.