Determination of lasalocid with sensitized terbium(III) luminescence detection

The luminescence of the lasalocid-terbium(III) system in the presence of Tr iton X-100 and trioctylphosphine oxide has been studied by obtaining kineti c and equilibrium measurements and using the stopped-flow mixing technique. The initial rate and luminescence signal of this system are directly propo rtional to the lasalocid concentration, which allows one to develop very si mple, fast, automatic methods for the determination of this analyte. Kineti c 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 mu g ml(-1) (ki netic method) and 0.01-5.0 mu g ml(-1) (equilibrium method) and the detecti on limits achieved were 1 and 3 ng ml(-1), respectively, equivalent to 2 an d 6 ng g(-1) lasalocid in a chicken liver sample, which are similar to thos e afforded by the chromatographic methods described for this determination. The relative standard deviation of both methods was close to 2%. The analy tical recoveries obtained by applying the kinetic and equilibrium methods t o drinking water, poultry feed and chicken liver samples ranged from 95.6 t o 102.1% and from 95.9 to 104.9%, respectively. (C) 1999 Elsevier Science B .V. All rights reserved.