Simultaneous determination of ciprofloxacin and tetracycline in biological fluids based on dual-lanthanide sensitised luminescence using dry reagent chemical technology Original Research Article

Terbium(III) and europium(III) have been used as dry reagents for the simultaneous determination of ciprofloxacin and tetracycline in serum and urine samples. These lanthanide ions were immobilised by adsorption in paper strips, which were previously treated with sucrose. The terbium(III)-ciprofloxacin chelate presents an intense luminescence at λex=284 nm and λem=545 nm and the europium(III)-tetracycline chelate does it at λex=395 nm and λem=615 nm. Luminescence measurements have been performed using the time-resolved mode. The linear ranges of the calibration graphs using standard solutions are 0.03–1.5 μg ml−1 for ciprofloxacin and 0.03–2.5 μg ml−1 for tetracycline and the calculated 3σ detection limits are 9 and 11 ng ml−1, for ciprofloxacin and tetracycline, respectively. Quantification limits (10σ) in the original human urine and serum samples were 125 and 1.3 μg ml−1, respectively, for ciprofloxacin, and 75 and 0.8 μg ml−1, respectively, for tetracycline. The features of the dry reagent method have been compared to those provided by the measurements carried out in solution. Mixtures of ciprofloxacin and tetracycline ranged in weight ratios between 5:1 and 1:10 were satisfactorily resolved with errors <6% using the dry reagent method, which was applied to the analysis of several serum and urine samples with recoveries ranging from 88.7 to 109.3%.