ORIGINAL PAPER Method for determination of fluoroquinolones based on the plasmonic interaction between their fluorescent terbium complexes and silver nanoparticles Mohammad Kamruzzaman & Al-Mahmnur Alam & Sang Hak Lee & Yeoun Suk Suh & Young Ho Kim & Gyu Man Kim & Sung Hong Kim Received: 18 February 2011 /Accepted: 30 May 2011 /Published online: 7 June 2011 # Springer-Verlag 2011 Abstract We report on a fluorometric method for the determination of the fluoroquinolones levofloxacin (LEV) and moxifloxacin (MOXI). It is based on the Tb(III)- sensitized luminescence that is plasmonically enhanced by silver nanoparticles (Ag NPs). The emission of the Tb(III) complexes has maximum at 545 nm after excitation at 284 nm and is strongly enhanced in the presence of the colloidal Ag NPs. Under optimum experimental conditions, luminescence intensity increases linearly with the concentration in the range from 4.16×10 -17 -3.59×10 -15 M of LEV, and from 4.98× 10 -17 -2.49×10 -15 M for MOXI with correlation coeffi- cients of 0.9996 and 0.9996, respectively. The limits of detection are 7.19×10 -18 M and 8.47×10 -18 M, respec- tively, and the relative standard deviations are 1.3 and 1.5% for 5 replicate measurements at 6.08×10 -14 M of LEV and 5.48×10 -14 M of MOXI. The method was successfully applied to the determination of LEV and MOXI in pharmaceutical samples, in urine and in serum. Keywords Fluorescence . Levofloxacin . Moxifloxacin . Terbium . Colloidal silver nanoparticles Introduction Fluoroquinolones (FQs) such as levofloxacin (LEV) and moxifloxacin (MOXI) are a new group of synthetic antibacterial agents with broad-spectrum activity for both of Gram positive and negative bacteria through inhibition of DNA gyrase [1]. They are the second generation of quinolone derivatives which obtained by the addition of a fluorine group in position 6 of quinolones and bearing a piperazinyl moiety at position 7 of quinolones [2]. The FQs produced by the modification of quinolones have high antibacterial properties in a wide range of application and improved bioavailability to combat infections caused by a microorganism [3]. FQs are useful antibacterial agents for treatment of an infection in a human body which could destroy pathogenic bacteria or prevent their growth because of their excellent pharmacokinetic profile, good tissue penetration and wide scope of activity. LEV (( -)-( S)-9-fluoro-2,3-dihydro-3-methyl-10-(4- methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de]-1,4-ben- zoxazine-6-carboxylic acid) exerts antibacterial activity via antagonism of the interaction between DNA gyrase and bacterial DNA to resist intracellular pathogens responsible for a typical pneumonia [4, 5]. LEV exhibits high potency and oral bioavailability, extensive tissue penetration, low Electronic supplementary material The online version of this article (doi:10.1007/s00604-011-0633-0) contains supplementary material, which is available to authorized users. M. Kamruzzaman : A.-M. Alam : S. H. Lee : Y . S. Suh Department of Chemistry, Kyungpook National University, Daegu 702-701, South Korea Y . H. Kim (*) Research Institute of Advanced Energy Technology, Kyungpook National University, Daegu 702-701, South Korea e-mail: youngkim@knu.ac.kr G. M. Kim School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, South Korea S. H. Lee (*) : S. H. Kim Korea Basic Science Institute Daegu Center, Daegu 702-701, South Korea e-mail: shlee@knu.ac.kr Microchim Acta (2011) 174:353–360 DOI 10.1007/s00604-011-0633-0