Photochemical fluorescence enhancement of the terbium-lomefloxacin complex and its application

The sensitized fluorescence intensity of the terbium ion (Tb(3+)) can be notably enhanced after the Tb(3+)-lomefloxacin(LFLX) complex system was irradiated by 365nm ultraviolet light. A photochemical reaction occurs to the irradiated Tb(3+)-LFLX complex. A new Tb(3+)system with intense fluorescence is obtained. On this basis a new sensitive and selective photochemical fluorimetry for the determination of LFLX was established. Under the optimal experimental conditions, the linear range of the determination is 2.0-500x10(-8) mol l(-1) for LFLX, and the detection limit is 6.0x10(-9) mol l(-1).Without any pre-treatment the recoveries of LFLX in human urine and serum were determined.     

Spectrofluorometric determination of trace amounts of coenzyme II using norfioxacin-terbium complex as a fluorescent probe.

When terbium ion (Tb3+)-norfloxacin (NFLX) complex is issued a fluorescent probe, in a buffer solution of pH = 7.6, NADP can remarkably enhance the fluorescence intensity of the Tb3+ -NFLX complex at lambda = 545 nm. The enhanced fluorescence intensity of Tb3+ is in proportion to the concentration of NADP. The dynamic range for the determination of NADP is 1.11 x 10(-7) - 6.16 x 10(-5) mol l(-1), with a detection limit of 4.31 x 10(-8) mol l(-1). This method is simple, practical and relatively free of interference from coexisting substances, so it can be successfully applied to determination of NADP in synthetic water samples.     

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+).     

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.     

Determination of ulifloxacin by terbium-sensitized fluorescence with second-order scattering and its applications.

This paper reports the determination of ulifloxacin (UFX) by terbium-sensitized fluorescence using a second-order scattering method. UFX and Tb(III) ion form a fluorescence complex in aqueous solution, and its maximum excitation and emission wavelengths are located at 273 and 545 nm, respectively. In optimum conditions, the relative intensity at 545 nm has a linear relationship to the concentration of UFX in the range of 2.0 x 10(-8) - 1.0 x 10(-5) mol L(-1) and the detection limit is 3.9 x 10(-9) mol L(-1). The proposed method was applied to the determination of UFX in spiked human serum and urine satisfactorily. The luminescence property of UFX is also discussed by comparing with norfloxacin (NFLX) and ofloxacin (OFLX).     

Terbium sensitized determination of tosufloxacin using electrochemiluminescence method.

A novel method for determination of trace amounts of tosufloxacin (TFLX) based on electrochemiluminescence (ECL) has been developed. The calibration graphs for TFLX were linear in the range of 5.0 x 10(-11)-3.5 x 10(-7) mol/L, with the detection limit of 1.3 x 10(-11) mol/L. Key factors affecting the determination of TFLX were investigated. TFLX amounts in capsule and serum samples were successfully detected by this method. A possible mechanism of energy transfer, and thus the explanation of ECL in the Tb3+-TFLX-Na2S2O4 system are discussed.     

Flow-injection analysis of two fluoquinolones by the sensitizing effect of terbium(III) on chemiluminescence of the potassium permanganate-sodium sulfite system

A simple, rapid and sensitive method for the determination of two fluoquinolones (FQs), enoxacin (ENX) and ofloxacin (OFLX) is described by using flow injection analysis with potassium permanganate-sodium sulfite chemiluminescence detection. The calibration graphs for ENX and OFLX are linear in the range of 8.0×10⁻¹⁰-1.0×10⁻⁵ and 1.0×10⁻⁹-1.0×10⁻⁶ mol l⁻¹, respectively. The 3σ limits of detection are 2.4×10⁻¹⁰ mol l⁻¹ for ENX and 5.6×10⁻¹⁰ mol l⁻¹ for OFLX. The method is applied satisfactorily to the determination of the two FQs in dosage form and urine sample. The possible mechanism is also proposed.     

Study on the electrochemiluminescence behavior of ABEI and its application in DNA hybridization analysis

The electrogenerated chemiluminescence (ECL) behavior of N-(4-aminobutyl)-N-ethylisoluminol (ABEI) was studied and it was found that ABEI could produce emission light when oxidized at a +1.0 V (vs. Ag/AgCl) potential in alkaline solution. The addition of H2O2 markedly improved the ECL sensitivity. The pH value of the solution as well as the H2O2 concentration and working potential all have influences on the ECL response. Under optimal conditions, ABEI can be detected in the range 1.3 x 10(-6)-6.5 x 10(-12) mol L(-1). A detection limit of 2.2 x 10(-12) mol L(-1) for ABEI was obtained at a signal-to-noise ratio of 3. ABEI was then used as a marker to label a known sequence oligonucleotide, which was used as a DNA probe for identifying a target ssDNA immobilized on a PPy modified electrode based on a specific hybridization reaction. The hybridization events were evaluated by the ECL measurements. The results showed that only a complementary sequence could form a double-stranded DNA with the DNA probe and give a strong ECL response. A three-base mismatch sequence and non-complementary sequence have no response. The intensity of the ECL was linearly related to the concentration of the complementary sequence in the range 9.6 x 10(-11)-9.6 x 10(-8) mol L(-1), the detection limit was 3.0 x 10(-11) mol L(-1).     

Determination of trace terbium(III) with N, N', N"-tri(3-indolemethanal)triaminotriethylamine based on a new fluorescence enhancement system.

A new Schiff-base ligand with a tripodal structure, N,N',N"-tri(3-indolemethanal)triaminotriethylamine (TTAIM), was synthesized. Its fluorescence intensity with terbium(III) was increased by about two orders of magnitude in the present of sodium acetate (NaAc). After the adding of the organic solvent dimethyl sulfoxide (DMSO) to the above system, leading to Tb3+ the fluorescence was further enhanced by about 16 fold. The spectrofluorimetric determination of a trace amount of Tb3+ based on this phenomenon was carried out. The excitation and emission wavelengths were 330 nm and 545 nm, respectively. Under the optimal conditions, the fluorescence intensities varied linearly with the concentration of Tb3+ in the range of 5.7 x 10(-11) - 6.3 x 10(-6) mol L(-1) with a detection limit of 5.0 x 10(-11) mol L(-1). The interferences of some rare earth metals and other inorganic ions were described. The method is a selective, sensitive, rapid and simple analytical procedure for the determination of terbium(III) in a high-purity yttrium oxide and synthetic sample. The mechanism for the fluorescence enhancement was also studied.     

Fluorimetric study of the interaction between human serum albumin and quinolones-terbium complex and its application

A highly sensitive spectrofluorimetric method is proposed for determination of human serum albumin (HSA) and some quinolone drugs. Using quinolones-terbium (Tb3+) complex as a fluorescent probe, in the buffer solution of pH 7.8, HSA can remarkably enhance the fluorescence intensity of the quinolones-Tb3+ complex at 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of HSA and quinolone drugs. Optimum conditions for the determination of HSA were also investigated. The linear ranges and limits of detection are 8.0 x 10(-9) to 8.0 x 10(-8) mol L(-1), 4.20 x 10(-9) mol L(-1) (for HSA); 1.0 x 10(-6) to 4.0 x 10(-6) mol L(-1), 1.87 x 10(-8) mol L(-1) (for norfloxacin) and 1.0 x 10(-7) to 1.0 x 10(-6) mol L(-1), 4.82 x 10(-8) mol L(-1) (for enoxacine), respectively. This method is simple, practical and relatively free interference from coexisting substances, as well as much more sensitive than most of the existing assays.     

The enhanced electrochemiluminescence of luminol on the nickel phthalocyanine modified electrode

A glassy carbon electrode (GCE) modified with nickel(II) tetrasulfophthalocyanine (NiTSPc) and Nafion was used for the investigation of the catalytic oxidation of luminol. The modified electrode was found to much more effectively improve the emission of electrochemiluminescence(ECL) of luminol in a solution containing hydrogen peroxide. The enhanced ECL signal corresponded to the catalytic oxidation of both luminol and H(2)O(2) by NiTSPc. Attached Ni(II) on GCE was oxidised to Ni(III) and then used as the catalyst for the chemiluminescence of luminol. The enhanced stability of the ECL signal with Nafion would mainly result from the prevention of the dissolution of NiTSPc and the adsorption of the oxidation product of luminol on the electrode surface. The proposed method enables a detection limit for luminal of 6.0 x 10(-8) mol L(-1) to be achieved in the presence of H(2)O(2) in the neutral solution. The enhanced ECL intensity had a linear relationship with the concentration of luminol in the range of 1.0 x 10(-7)-8.0 x 10(-6) mol L(-1).     

Flow-injection electrogenerated chemiluminescence detection of hydrazine based on its in-situ electrochemical modification at a pre-anodized platinum electrode

In this paper. it was found that the enhancing effect of hydrazine on the weak electrogenerated chemiluminescence (ECL) signal of the electrooxidation of luminol at a pre-anodized platinum electrode was stronger than that of hydrazine at a bare platinum electrode. Based on this finding and the combination of this finding with a flow-injection technique, a novel, sensitive and selective ECL method for hydrazine was developed. Under the optimum experimental conditions, the relative ECL intensity was linear with hydrazine concentration over the range 2.0 x 10(-8) - 5.0 x 10(-5) mol L(-1), with a detection limit of 6.0 x 10(-9) mol L(-1).     

Flow-injection electrogenerated chemiluminescence determination of isoniazid using luminol.

Based on a new electrogenerated chemiluminescence (ECL) analytical idea, this paper explains a sensitive and selective flow-injection ECL method using luminol for the determination of isoniazid, based on the sensitizing effect of isoniazid for the weak ECL emission of electrochemically oxidized luminol. Under the optimum experimental conditions, the relative ECL intensity was linear with isoniazid concentration in the range of 4.0 x 10(-8) mol/L to 8.0 x 10(-6) mol/L and with a detecting limit of 2.8 x 10(-8) mol/L.     

Homogenous electrogenerated chemiluminescence immunoassay for human immunoglobulin G using N-(aminobutyl)-N-ethylisoluminol as luminescence label at gold nanoparticles modified paraffin-impregnated graphite electrode

A homogeneous electrogenerated chemiluminescence (ECL) immunoassay for human immunoglobulin G (hIgG) has been developed using a N-(aminobutyl)-N-ethylisoluminol (ABEI) as luminescence label at gold nanoparticles modified paraffin-impregnated graphite electrode (PIGE). ECL emission was electrochemically generated from the ABEI-labeled anti-hIgG antibody and markedly increased in the presence of hIgG antigen due to forming a more rigid structure of the ABEI moiety. The concentration of hIgG antigen was determined by the increase of ECL intensity at a gold nanoparticles modified PIGE. It was found that the ECL intensity of ABEI in presence of hydrogen peroxide was dramatically enhanced at gold nanoparticles modified PIGE in neutral aqueous solution and the detection limit of ABEI was 2 x 10(-14)mol/L (S/N=3). The integral ECL intensity was linearly related to the concentration of hIgG antigen from 3.0 x 10(-11) to 1.0 x 10(-9)g/mL with a detection limit of 1 x 10(-11)g/mL (S/N=3). The relative standard deviation was 3.1% at 1.0 x 10(-10)g/mL (n=11). This work demonstrates that the enhancement of the sensitivity of ECL and ECL immunoassay at a nanoparticles modified electrode is a promising strategy.     

Determination of heparin using ciprofloxacin-Tb3+ as a fluorescence probe.

A new spectrofluorometric method was developed for the determination of trace amounts of heparin (Hep). Using ciprofloxacin (CIP)-terbium (Tb3+) as a fluorescent probe, in a buffer solution of pH 7.20, Hep can remarkably enhance the fluorescence intensity of the CIP-Tb3+ complex at lambda = 545 nm; also, the enhanced fluorescence intensity the Tb3+ ion is proportional to the concentration of Hep. The optimum conditions for the determination of Hep were also investigated. The dynamic range for the determination of Hep is 0.1 - 1.2 microg ml(-1) with a detection limit of 6.89 ng ml(-1). This method is simple, practical and relatively free of interference from coexisting substances, and can be successfully applied to assess Hep in biological samples. By the Rosenthanl graphic method, the association constant and binding numbers of heparin with the probe are 2.44 x 10(5) l mol(-1) and 19.7. Moreover, the enhancement mechanisms of the fluorescence intensity in the CIP-Tb3+ system and the CIP-Tb3+-Hep system have also been considered.     

The enhanced electrogenerated chemiluminescence of Ru(bpy)3(2+) by glutathione on a glassy carbon electrode modified with some porphine compounds

It has been found that the electrochemical activity of glutathione was increased greatly at the glassy carbon electrodes modified with 5,10,15,20-tetraphenylporphine ruthenium(II) carbenyl (RuTPP), meso-tetraphenylporphine copper(II) complex (CuTTP) and hemin. It has been also found that glutathione would enhance the electrogenerated chemiluminescence (ECL) of Ru(bpy)3(2+) at a hemin glassy carbon electrode; the enhanced ECL intensity was linear with the concentration of glutathione in the range of 1 x 10(-7)-1 x 10(-4) mol l-1, based on which method for determination of glutathione has been developed. The detection limit of glutathione was 2 x 10(-8) mol l-1, and the relative standard deviation for 1 x 10(-6) mol l-1 glutathione was 2.7%. The mechanism for this ECL system has been proposed.     

Pulse injection analysis with chemiluminescence detection: determination of citric acid using tris-(2,2'-bipyridine) ruthenium(II)

A chemiluminescence method for the determination of citric acid was developed. The method is based on the enhancement of citric acid on the chemiluminescence light emission of tris-(2,2'-bipyridine)ruthenium(II). In the presence of tris-(2,2'-bipyridine)ruthenium(II), upon the addition of Ce(IV), resulted in intense light emission. The emission intensity is greatly enhanced by the presence of citric acid. The linear range and detection limit of citric acid are 3.0x10(-8) approximately 6.0x10(-6) mol l(-1) and 3.0x10(-8) mol l(-1), respectively. The precision of the proposed method is determined by analyzing 11 samples containing 1.0x10(-7) mol l(-1) citric acid. The relative standard deviation is 3.0%. The enhanced mechanism of citric acid was studied. The method was evaluated by carrying out an interference study with common ions and compounds, by a recovery study and by analysis of human urine and orange juice. A satisfactory result was obtained.     

Tris(2,2'-bipyridyl)ruthenium(II)-zirconia-Nafion composite films applied as solid-state electrochemiluminescence detector for capillary electrophoresis

The major goal of this work was to develop a new solid-state electrochemiluminescence (ECL) detector suitable for capillary electrophoresis (CE). The detector was fabricated by coating a sol-gel derived zirconia (ZrO(2))-Nafion composite film on a graphite electrode, then the zirconia-Nafion modified electrode was immersed in tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3) (2+)) solution to immobilize this active chemiluminescence reagent. The voltammetric and ECL behaviors of the detector were investigated and optimized in tripropylamine solution. The ratio of 53% for zirconia in the zirconia-Nafion composite provided the highest luminescence intensity of immobilized Ru(bpy)(3) (2+). The ECL can maintain its stability very well in the phosphate solution in the period of 5-90 h when the solid-state ECL detector was immersed in the solution all the time. The optimum distance of capillary outlet to the solid-state ECL detector has been found to be ca. 50-80 microm for a 75 microm capillary. The effects of ionic strength and pH of ECL solution on peak height were investigated. The CE with solid-state ECL detector system was successfully used to detect tripropylamine, lidocaine, and proline. The detection limits (S/N = 3) were 5 x 10(-9) mol.L(-1) for tripropylamine, 1 x 10(-8) mol.L(-1) for lidocaine and 5 x 10(-6) mol.L(-1) for proline, and the linear ranges were from 1.0 x 10(-8) to 1.0 x 10(-5) mol.L(-1) for tripropylamine, 5.0 x 10(-7) mol.L(-1) to 1.0 x 10(-5) mol.L(-1) for lidocaine and 1.0 x 10(-5) to 1.0 x 10(-3) mol.L(-1) for proline, respectively.     

Fluorimetric determination of ascorbic acid in vitamin C tablets using methylene blue

In this study, a simple and sensitive fluorimetric method was described for the determination of Ascorbic Acid (AA). The procedure is based on the reaction between AA and Methylene Blue (MB). The fluorescence intensity of MB was measured at excitation and emission of 664 and 682 nm, respectively. MB concentration was decreased as a function of decreasing fluorescence intensity due to forming colorless form of MB (Leuco-MB) in the reaction between AA and MB. A linear relationship was obtained between the decreasing fluorescence intensity and the concentration of AA in the range of 3.0 x 10(-7)-6.0 x 10(-6) mol.l(-1). The detection limit was 2.5 x 10(-7) mol.l(-1). The proposed method was applied successfully for the determination of AA in Vitamin C tablets.     

Tris(2,2'-bipyridine)ruthenium(II) electrogenerated chemiluminescence of alkaloid type drugs with solid phase extraction sample preparation

An electrogenerated chemiluminescence (ECL) method for the determination of pethidine, atropine, homatropine and cocaine is described. The optimum conditions were found to be similar for all of these compounds although the ECL emission intensity for cocaine was an order of magnitude lower than for pethidine due to their different chemical structures. Linear calibrations were obtained for all the compounds at pH 10 in borate buffer (0.05 mol l-1) at 1.3 V. Limits of detection of 6.8 x 10(-8), 2.2 x 10(-7), 3.2 x 10(-7) and 6.5 x 10(-7) mol l-1, respectively, were achieved for pethidine, atropine, homatropine and cocaine in standard solutions. Solid-phase extraction was used to separate the drugs from their matrix and the method was applied to the determination of spiked urine samples. The limits of quantitation for pethidine, atropine, homatropine and cocaine in urine were 1.0 x 10(-6), 2.0 x 10(-6), 2.0 x 10(-6) and 4.0 x 10(-6) mol l-1, respectively, with recoveries of between 90 and 110%.