PIXE and micro-PIXE studies on the distribution of metal ions in environmental and biological samples

PIXE--Proton Induced X-ray Emission is a novel and powerful tool for non-destructive multi-element analysis with excellent sensitivity. This technique has been applied to several biological and environmental studies at the University of Arizona. The first application reported here is the study of carrot tissue samples, obtained from plants irrigated with uranium, molybdenum, selenium or manganese contaminated water. The carrots were analyzed with PIXE for the concentrations of these elements taken up by the plants from water. The standard addition method along with an added internal standard was utilized for the study of thick targets made from carrot powder. ICP was also used to analyze the same samples for purposes of comparison. Excellent agreement was found between the PIXE and ICP results. The second study with the PIXE technique was to measure the uptake of mercury by the kidney. Mercury tubule suspensions from the rabbit kidney were incubated with various mercury compounds and enzymes and analyzed with PIXE for their mercury content. Mercury was successfully fixed by exposing the tubule or tissue samples to hydrogen sulfide to convert all forms of mercury to mercury(II) sulfide. Saturated and unsaturated chlorinated aliphatic hydrocarbons are often found as contaminants in ground water. A palladized-iron bimetallic system can be used to completely dechlorinate these compounds. The third application of PIXE was to study the surface of the bimetallic system before and after dechlorination and acid regeneration. There were no significant changes in the surface composition before and after dechlorination. A dilute hydrochloric or oxalic acid solution could be used to regenerate the palladized iron surface