Development of a Colorimetric Test for Uranium

摘要

This paper discusses the development of and proposed enhancements to a colorimetric test for the detection of uranium in biological samples such as urine. The goal of this work is to develop a technique for the detection of uranium that could: (1) be conducted rapidly and accurately; (2) would not require extensive sample preparation; (3) would not require expensive or complicated instrumentation; (4) would require little or no technical training to conduct; and (5) could be used in a field situation if needed. The technique described in this paper involves the following steps. A buffer is added to the sample to maintain the pH of the mixture within an experimentally acceptable range and a quaternary ammonium salt is added to aid in solubilization of the reaction components. A pyridylazo stain, 2-(5-bromo-2-pyridylazo)-5- diethylaminophenol, capable of binding a variety of metals, is used to complex the uranium. This interaction has been made specific for uranium through the use of 'masking agents.' Color development indicating the presence of uranium is monitored and can be quantitated by determining the absorbance of the reaction mixture at 578 nm, using a spectrophotometer or colorimeter. At present, the limit of sensitivity of the procedure is approximately 30 g of uranium/L. However, through the incorporation of a sample concentration step in the procedure, we believe we can greatly increase the sensitivity of the technique. The two areas we believe are amenable to our concentration efforts are prior to the addition of the assay components (pre-complexation concentration step) or after the formation of the stain/uranium complex (post- complexation concentration step). Our goal is to make the procedure more applicable while still maintaining technical simplicity and ease of use.