A study on silver nanoparticles-sensitized fluorescence and second-order scattering of the complexes of Tb(III) with ciprofloxacin and its applications.

Fluorescence of terbium(III) is sensitized when excited in the presence of ciprofloxacin (CPLX) in the aqueous solution because a Tb(III)-CPLX complex is formed and the maximum fluorescence peak locates at 545 nm. The second-order scattering (SOS) peak at 545 nm also appears for the Tb(III)-CPLX complexes with the excitation wavelength of 272 nm. The intensity at 545 nm obviously increases when the silver nanoparticles are added to the Tb(III)-CPLX system, and the relative intensity is proportional to the concentration of CPLX. Based on this phenomenon, a new method for the determination of CPLX has been developed by using a common spectrofluorometer to measure the intensity of fluorescence and SOS. The intensity is enhanced most by silver nanoparticles at pH 6.0. The calibration graph for CPLX is linear in the range of 3.0 x 10(-9) to 1.0 x 10(-5) mol l(-1). The detection limit is 8.5 x 10(-10) mol l(-1). The method was applied satisfactorily to the determination of CPLX in tablets and capsules. The results show that silver nanoparticles with certain size and concentration can enhance the fluorescence and SOS intensity of the system.

[Nanosilver sensitized fluorescence and second-order scattering of Tb (III)-norfloxacin and its application].

Norfloxacin (NFLX) can form complex with Tb(III) ion, and the intramolecular energy transfer from NFLX to Tb (III) takes place when excited. And thus the characteristic fluorescence of Tb (III) ion is enhanced and the maximum fluorescence peak locates at 545 nm. The second-order scattering (SOS) peak at 545 nm also appears for the Tb (III)-NFLX complex with the excitation wavelength of 272 rnm. When the silver nanoparticles were added to the Tb (III)-NFLX binary system, the luminescence intensity at 545 nm greatly increased. And the relative intensity is proportional to the amount of NFLX. Based on this phenomenon, a novel method for the determination of NFLX has been developed by using a common spectrofluorometer to measure the intensity of fluorescence and SOS. The calibration graphs for NFLX are linear in the range of 6.0 x 10(-9)-1.0 x 10(-5) mol x L(-1), and the detection limit is 4.4 x 10(-9) x mol x L(-1). This method was applied satisfactorily to the determination o f NFLX in capsule and eye drop samples. The experimental results showed that it is the certain size and certain concentration of silver nanoparticles that can greatly enhance the fluorescence-SOS intensity.

Determination of norfloxacin using a terbium-sensitized electrogenerated chemiluminescence method.

A simple electrogenerated chemiluminescence (ECL) analysis method for the determination of norfloxacin (NFLX) is reported. It is based on ECL produced by Na(2)SO(3), which is sensitized by the Tb-NFLX complex. The relative ECL intensity of the Tb(3+)-NFLX-Na(2)SO(3) system is proportional to the amount of NFLX. The optimized experimental conditions were investigated. The linear range and detection limit for NFLX were 1.0 x 10(-10)-8.0 x 10(-7) mol/L and 2.8 x 10(-11) mol/L, respectively. This method was successfully applied to the determination of NFLX in a capsule. NFLX in urine can be directly detected without pretreatment or separation.

Electrochemiluminescence of terbium (III)-two fluoroquinolones-sodium sulfite system in aqueous solution.

The electrochemiluminescence (ECL) of Tb3+-enoxacin-Na2SO3 system (ENX system) and Tb3+-ofloxacin-Na2SO3 system (OFLX system) in aqueous solution is reported. ECL is generated by the oxidation of Na2SO3, which is enhanced by Tb3+-fluoroquinolone (FQ) complex. The ECL intensity peak versus potential corresponds to oxidation of Na2SO3, and the ECL emission spectra (the peaks are at 490, 545, 585 and 620 nm) match the characteristic emission spectrum of Tb3+, indicating that the emission is from the excited state of Tb3+. The mechanism of ECL is proposed and the difference of ECL intensity between ENX system and OFLX system is explained. Conditions for ECL emission were optimized. The linear range of ECL intensity versus concentrations of pharmaceuticals is 2.0 x 10(-10) -8.0 x 10(-7)mol l(-1) for ENX and 6.0 x 10(-10) -6.0 x 10(-7)mol l(-1) for OFLX, respectively. A theoretical limit of detection is 5.4 x 10(-11)mol l(-1) for ENX and 1.6 x 10(-10)mol l(-1) for OFLX, respectively. The ECL was satisfactorily applied to the determination of the two FQs in dosage form and urine sample.

[A study on europium sensitized chemiluminescence of pipemidic acid].

A flow injection chemiluminescence method for the determination of Pipemidic acid (PPA) was developed. It is based on luminescence produced with KMnO4-Na2S2O4 CL system sensitized by Eu3+-PPA. The familar excipients such as starch and dextrine do not cause interference. The several kinds of affect on chemiluminescence were studied. The linear range and detection limit for PPA are 7.00 x 10(-9)-9.00 x 10(-7) mol x L(-1) and 4.09 x 10(-9) mol x L(-1), respectively. This method have successfully been applied to the determination of PPA in tablet and urine. And the mechanism of chemiluminescence is proposed.

Determination of lomefloxacin by terbium sensitized chemiluminescence method.

A simple, rapid and sensitive chemiluminescence (CL) method was proposed for the determination of lomefloxacin (LFX). This method is based on the fact that the weak CL from the redox reaction of Ce(4+)-Na(2)SO(3) can be greatly enhanced by the complex of Tb(3+)-LFX. The CL intensity is directly proportional to the concentration of LFX in the range 2.0x10(-9) to 1.0x10(-5) mol L(-1), and the detection limit (S/N=3) is 1.1x10(-9) mol L(-1). This method has been applied to the detection of LFX in pharmaceutical preparation, urine and serum samples. Recoveries were in the range 95-105%. The CL mechanism of Ce(4+)-Na(2)SO(3)-Tb(3+)-LFX system was proposed to be an intermolecular energy transfer from excited SO(2)(*) to LFX and an intramolecular energy transfer from LFX to Tb(3+).

Fleroxacin hydrochloride hydrate.

In the structure of the title compound, 4-[3-carboxy-6,8-difluoro-1-(2-fluoroethyl)-1,4-dihydro-4-oxo-7-quinolyl]-1-methylpiperazinium chloride hydrate, C(17)H(19)F(3)N(3)O(3)(+).Cl(-).H(2)O, the quinoline and its substituents, except for the fluoroethyl group, are coplanar, while the piperazinium moiety exists in a chair form. There are pi-pi-stacking interactions between the quinoline rings, and intra- and intermolecular hydrogen bonds in the crystal.