Flow-injection chemiluminescence determination of enrofloxacin using the Ru(phen)3(2+)-Ce(IV) system and central composite design for the optimization of chemical variables.

The main purpose of this study was to develop an inexpensive, simple, rapid and sensitive chemiluminescence (CL) method for the determination of enrofloxacin (ENRO) using a flow-injection system. This method is based on rapid reduction of Ru(phen)(3)(3+), which is produced in the reaction between Ru(phen)(3)(2+) and acidic Ce(IV) by ENRO, producing strong CL. A central composite design (CCD) was used for optimization of the chemical variables. Regression analysis of the data from the CCD demonstrated that a second-order polynomial model is an adequate description of the surface over the factor limits studied. Optimization using CCD gave approximately four-fold better results than the single-factor-at-a-time method. Under optimal experimental conditions, the CL response was proportional to the concentration of ENRO over a wide range (0.008-3.6 microg/mL) with a correlation coefficient of 0.9986 and a detection limit of 0.003 microg/mL (3sigma). The relative standard deviation for 11 repeated determinations of 0.14 microg/mL ENRO was 4.2%. This method was successfully applied to the analysis of commercial formulations, spiked plasma and spiked poultry tissue. Sample analyses showed good recovery percentages for drugs and spiked plasma (95.1-103.9%). Recovery percentages for spiked poultry tissue were in the range 77.6-87.3%. The minimum sampling rate was 100 samples/h.