Progress toward the determination of Sr2+ in highly basic solutions using imaging optical fiber sensor arrays

Abstract

This manuscript describes initial progress toward the development of an imaging optical fiber microsphere sensor array for real-time monitoring of Sr²⁺ in process streams from high-level radioactive waste (HLW) remediation. Fura-2, a fluorescent molecular recognition compound, which displays increased fluorescence intensity upon complexation with divalent cations, was employed as a probe to quantify Sr²⁺. The solution-based detection of Sr²⁺ using Fura-2 was investigated in the presence of low Ca²⁺ concentrations and at high pH and ionic strength. A linear range of 6.7 × 10⁻⁷ M to 6.7 × 10⁻⁴ M was obtained for Sr²⁺ in neutral solutions containing trace Ca²⁺ and 6.7 × 10⁻⁸ M and 6.7 × 10⁻⁴ M for Sr²⁺ in high pH, high ionic strength solutions. Additionally, the stability of imaging optical fibers to harsh, high pH conditions was examined. These experiments suggest the fiber surface may need to be modified so that they are stable during the anticipated measurement times required for HLW.