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 λ=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 × 10 −8  mol/L to 5.5 × 10 −7  mol/L and 1.1 × 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. J. Clin. Lab. Anal. 21:207–212, 2007. © 2007 Wiley‐Liss, Inc.