Patent ID: 6228651
Filing Date: 2001-05-08
Classification: C01B,H01L,Y10S,Y10T

Abstract:
A process for the preparation of an analytical sample for use in quantitative analysis of a radioactive impurity in phosphoric acid, comprising:heating said phosphoric acid to a temperature of between about 120.degree. to 170.degree. C.;adding an isotope of the radioactive impurity as a tracer:dipping, with heating, for a time period sufficient to reduce the impurity content to a level of not more than 10.sup.-3 Bw/mL as defined by the concentration of the radioactive impurity in the phosphoric acid, a semiconductor base in said phosphoric acid as heated to deposit the impurity from said phosphoric acid onto said semiconductor base; andremoving said semiconductor base, having deposited thereon said impurity, from said phosphoric acid to use the same as said analytical sample.