Study of micellar solutions to enhance the europium-sensitized luminescence of tetracyclines

Abstract

The luminescence emission from the complexes between Eu^III and tetracyclines was found to be greatly enhanced by surfactants. Under optimum conditions, viz., pH 8.0 and 1.0% m/v cetylpyridinium chloride or Triton X-100 surfactant, an enhancement by a factor of up to approximately 34 was observed for some tetracyclines. Small structural differences between the various tetracyclines studied had a marked effect on the intensity of emission. The luminescence of the Eu^III–tetracycline–Triton X-100 system was shown to be quenched by free Eu^III ions and followed the Stern–Volmer equation for collisional quenching provided that an allowance was made for the native emission from the free Eu^III. The luminescence intensity for tetracycline was linear over the concentration range from 2.0 × 10^–8 to 1.0 × 10^–5 mol dm^–3 with a detection limit of about 2 × 10^–9 mol dm^–3(three standard deviations of the blank).