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

Abstract

The luminescence emission from the complexes between EuIII 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 EuIII–tetracycline–Triton X-100 system was shown to be quenched by free EuIII ions and followed the Stern–Volmer equation for collisional quenching provided that an allowance was made for the native emission from the free EuIII. 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).