- P-ISSN 1225-0163
- E-ISSN 2288-8985
The analytical method to determine europium(III) ion in aqueous solution by fluorescence spectroscopy based upon the conformational change of calmodulin in the presence of the analyte has been studied. The fiber optic chemical sensor used in this study was constructed by entrapping a fluorescein-labeled calmodulin solution, EGTA, buffer solution at the common end of a bifurcated fiber optic bundle by means of a dialysis membrane. The calibration curve to determine europium(III) ion was obtained when concentration of calmodulin, concentration of EGTA, Tris-HCl buffer solution, pH, excitation wavelength and fluorescence wavelength were <TEX>$5.0{\times}10^{-5}M$</TEX>, 0.50 mM, 5.0 mM, 7.0, 495 nm and 520 nm, respectively. The detection limit was <TEX>$1.0{\times}10^{-11}M$</TEX> and the working range of the calibration curve for the sensor was <TEX>$1.0{\times}10^{-11}M{\sim}1.0{\times}10^{-9}M$</TEX>. The response time was 15 minutes. For the determination of europium(III) ion by the present method, <TEX>$Na^+$</TEX> and <TEX>$K^+$</TEX> ions did not interfere but <TEX>$Ca^{2+}$</TEX> ion seriously interfered.