Determination of Doxycycline by Europium Ion Fluorescence Probe Sensitized by Surfactant

The fluorescence property of europium（Ⅲ）-doxycycline（DC） complex and the effect of reaction condition were studied. It is found that in the buffer solution of Na2B4O7-NaOH at pH 9.63 europium can react with doxycycline to form a complex. After intramolecular energy transfer, the system shows the characteristic fluorescence of Eu 3+. The fluorescence intensity can be enhanced again in addition of non-ionic surfactant Triton X-100 with λ_ ex=375 nm, λ_ em=617 nm. Based on this, a new method using europium ion as fluorescent probe for the determination of trace doxycycline was proposed. The fluorescence intensity is linearly related to the doxycycline concentration in the range of 2.8×10 -6～2.46×10 -5 mol·L -1 with correlation coefficient 0.9973. The detection limit was 1.35×10 -8 mol·L -1. It is applied to the determination of doxycycline in pharmaceutical preparations and in serum satisfactorily. The recovery is within the range of 93%～103%.