Spectrofluorimetric determination of bile acid using a europium-doxycycline probe.

A new spectrofluorimetric method was developed for the determination of trace amounts of bile acid (BA). Using europium ion (Eu(3+))-doxycycline (DC) as a fluorescent probe, in a buffer solution of pH=7.0, BA can remarkably reduce the fluorescence intensity of the DC-Eu(3+) complex at lambda=612 nm; the reduced fluorescence intensity of the Eu(3+) is proportional to the concentration of BA. Optimum conditions for the determination of BA were also investigated. The linear range and detection limit for the determination of BA were 5.0 x 10(-8) mol/L to 5.5 x 10(-7) mol/L and 1.1 x 10(-8) mol/L, respectively. This method is practical and relatively free of interference from coexisting substances, and can be successfully applied to assess BA in serum samples.