Determination of Sr in soil by tungsten coil atomic emission spectrometry

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 mu m syringe filter. Twenty-five mu L 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. (C) 2011 Elsevier B.V. All rights reserved.