Determination of lasalocid with sensitized terbium(III) luminescence detection

The luminescence of the lasalocid-terbium(III) system in the presence of Triton X-100 and trioctylphosphine oxide has been studied by obtaining kinetic and equilibrium measurements and using the stopped-flow mixing technique. The initial rate and luminescence signal of this system are directly proportional to the lasalocid concentration, which allows one to develop very simple, fast, automatic methods for the determination of this analyte. Kinetic and equilibrium data can be obtained in only 0.1 and 10 s, respectively. The calibration graphs were linear over the range 0.004-5.0 mug ml(-1) (kinetic method) and 0.01-5.0 mug ml(-1) (equilibrium method) and the detection limits achieved were 1 and 3 ng ml(-1), respectively, equivalent to 2 and 6 ng g(-1) lasalocid in a chicken liver sample, which are similar to those afforded by the chromatographic methods described for this determination. The relative standard deviation of both methods was close to 2%. The analytical recoveries obtained by applying the kinetic and equilibrium methods to drinking water, poultry feed and chicken liver samples ranged from 95.6 to 102.1% and from 95.9 to 104.9%, respectively.