Determination of Sr in soil by tungsten coil atomic emission spectrometry
Abstract Strontium was determined in soil by tungsten coil atomic emission spectrometry (WCAES). Since aluminum enhances strontium emission and is a common component of soil, it was first necessary to develop a method to remove aluminum from digested soil solutions. This was accomplished by buffering solutions to a pH of 5.5 with ammonium bicarbonate. Each buffered solution was filtered through a 0.45 μm syringe filter. Twenty-five μL of the filtrate were injected into a WCAES instrument and analyzed. The method effectively removed aluminum from digested samples. The next goal was to develop a fast soil digestion method that could be used in field analyses. A potential application for a fast method is the detection of radioisotopes after the detonation of a radioactive dispersion device (dirty bomb). Such devices could potentially contain strontium-90, and a field method would be necessary to quickly determine the concentration of strontium. Two different soil digestion methods were tested. The first (method A) was a typical method using aqua regia, hydrogen peroxide, and heat. The second (method B) was a faster method that involved shaking soil with concentrated acid for 30 s. Strontium spike recoveries showed that method B was not as effective at recovering strontium from soil. The % strontium recoveries (method B) were 87% compared to 93% for method A. A NIST SRM San Joaquin Soil was analyzed using both soil digestion methods. Strontium recoveries were 76% and 59% for methods A and B respectively, suggesting that digestion conditions needed to be more thorough.