Application of proton induced x-ray emission to the qualitative and quantitative analysis of iodine in biological samples

Particle-induced x-ray emission (PIXE) was applied to evaluate the loss of volatile elements such as iodine in biological samples. The analytical quality of the method is comparable or better than spectrophotometry. The temperature dependence of volatility loss of trace iodine was characteristic, and the feature was divided into three temperature regions. The first one (20-200 deg C) showed only a slight loss below 20% on drying; the second one (200-350 deg C) where carbonizing processes became prominent, showed a remarkable loss up to 50%. The last one, beyond 350 deg C, was accompanied by a considerable loss of iodine (more than 80%) with ashing. Even in the analysis using low temperature ashing with oxygen plasma, the loss of iodine observed was considerable (nearly 80%). The significance of these findings by PIXE in trace analysis is noted to improve analytical quality of volatile elements, such as iodine, in biological, medical and environmental fields. (author)