With the exception of studies of the radiation chemistry of relatively dilute and essentially pure aqueous solutions of substances that may serve as analytical reagents, little research has been carried out to establish the effects of radiation on analytical chemistry methods. In the last several decades and, in particular, with the advent of nuclear power reactors, it has become necessary to carry out analytical procedures under conditions of fairly high levels of radiation. The effect of both the kind and level of radiation on the specific methods has not been established except in a very few cases t'2. The exact effect can only be determined by radiation experiments under the same conditions under which the procedures must be performed.
The determination of trace amounts of iron under conditions of high levels of radiation has become increasingly important. A great deal of research is being carried on to determine corrosion rates in the various types of reactors and reactor vessels being used. In many cases, the primary materials being studied are iron-based alloys. The results of such studies must, of necessity, be based on the ability to determine quickly and accurately trace amounts of iron. Colorimetric or spectrophotometric methods are, therefore, a natural and logical solution to meet this need. Probably the most widely used colorimetric methods for the determination of trace amounts of iron are based on use of the following three reagents: thiocyanate 3, 1,10phenanthroline 4, and a,~'-bipyridyl 5. The latter two methods are currently used in this laboratory for the determination of iron in reactor materials under remote handling conditions and high levels of radiation.
In this study the effect of relatively high levels of y-radiation on the accuracy and precision of the three above-mentioned methods was determined.
EXPERIMENTAL
Apparatus
Irradiation of the samples was carried out in pre-irradiated Β½-ounce glass bottles placed in reproducible positions with respect to a 300-curie cobalt-60 source. The dose rates in these positions, as determined by Fricke dosimeter 6, were of the order of 6-104 rad h -1. The dose rate was determined periodically over the period of time covered by the investigation. All work was carried out at ambient temperature.