STUDY OF CHEMICAL ETCHING PROCEDURE USED TO REMOVE SURFACE OXYGEN CONTAMINATION IN CHARGED PARTICLE ACTIVATION ANALYSIS
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In charged particle activation analysis, the procedure used to eliminate surface oxygen contamination is to use a single post-irradiation chemical etch deep enough to remove the activated surface layer including recoil activity. Fluorine-18 is the radioisotope produced by most analytically useful charged particle reactions with oxygen. It is assumed with this procedure that adsorbed activity from the etching solution onto the sample surface can be neglected. However, the results of this experimental study show that adsorbed fluorine-18 activity can become a significant source of error in the determination of oxygen in aluminum matrices. For example in the case of a helium-3 activation, the determination of 10 ppb oxygen would be affected by an error of approximately 500%. It was found that this potential interference can be eliminated by using a post-irradiation etching procedure which employed two successive etches, the first to remove the activated oxide layer and recoil activity, and the second, of less than 5 microns per face, to remove adsorbed activity. 1968, American Chemical Society. All rights reserved.
