A new probe based on the complex of 1,2 dihydro-2-oxoquinoloine-4-carboxylic acid (DOCA) as a ligand with Europium (III) ion was developed for the quantitation of Moxifloxacin HCl (Moxi.HCl) in pharmaceuticals and human plasma using a luminescence method. The metal to ligand ratio of the complex is 1:2 as determined by a Job plot. The determination of Moxi.HCl is based on static quenching of the luminescence of the probe upon coordination of Moxi.HCl. The negative value for Delta G proves that this reaction is spontaneous. The calibration curve was constructed based on a Stern-Volmer equation and the quantitation range was 0.05-80 mu g mL(-1). This is low enough to determine the drug in blood plasma, even hours after administration, which is not feasible with the methods published so far. The LOD was 15 ng mL(-1). The accuracy of the method was demonstrated by good recoveries of spiking experiments in tablets, ophthalmic eyedrops and human blood plasma, where the mean recovery was 99% with RSDs below 5%. The method was validated by closely matching concentrations of the drug found in all these real samples by HPLC. Additionally, Moxi.HCl can be assessed semi-quantitatively by eye vision upon excitation with a UV lamp at 365 nm by a gradual color shift from red to blue with increasing concentrations of Moxi.HCl.