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.     

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.     

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.     

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+).     

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.     

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.     

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.     

Spectrofluorimetric determination of trace heparin using lomefloxacin-terbium probe

A new spectrofluorimetric method was developed for determination of trace amount of heparin (Hep). Using lomefloxacin (LOM)-terbium ion (Tb3+) as a fluorescent probe, in the buffer solution of pH 8.70, Hep can remarkably enhance the fluorescence intensity of the LOM-Tb3+ complex at lambda = 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of Hep. Optimum conditions for the determination of Hep were also investigated. The linear range for the determination of Hep was 0.6-2.0 microg/ml and the detection limit was 45.22 ng/ml. 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 of Hep with the probe is 4.56 x 10(4) l/mol and binding numbers is 18.2. Moreover, the enhancement mechanism of the fluorescence intensity in the LOM-Tb3+ system and the LOM-Tb3+-Hep system have also been discussed.     

Electrochemiluminescent determination of L-cysteine with a flow-injection analysis system.

A flow-injection electrochemiluminescent method for L-cysteine determination has been developed based on its enhancement of the electrochemiluminecence of luminol at a glassy carbon electrode. This method is simple and sensitive for cysteine determination. Under the selected experimental parameters, the linear range for cysteine concentration was 1.0 x 10(-6) - 5.0 x 10(-5) mol/l, and the detection limit was 0.67 micromol/l (S/N = 3). The relative standard deviation for 11 measurements of 1.0 x 10(-5) mol/l cysteine was 4.5%. The proposed method has been applied to the detection of cysteine in pharmaceutical injections with satisfactory results.     

Determination of diclofenac sodium by capillary zone electrophoresis with electrochemical detection

Capillary zone electrophoresis was employed for the determination of diclofenac sodium using an end-column amperometric detection with a carbon fiber microelectrode, at a constant potential of 0.83 V vs. saturated calomel electrode. The optimum conditions of separation and detection are 4.90 x 10(-3) mol/l Na2HPO4-3.10 x 10(-3) mol/l NaH2PO4 (pH 7.0) for the buffer solution, 10 kV for the separation voltage, 5 kV and 10 s for the injection voltage and the injection time, respectively. The limit of detection is 2.5 x 10(-6) mol/l or 5.2 fmol (S/N=2). The relative standard deviation is 0.8% for the migration time and 4.7% for the electrophoretic peak current. The method was applied to the determination of diclofenac sodium in human urine.     

Determination of the pesticide carbaryl by chemical deoxygenation micellar-stabilized room temperature phosphorescence

This paper presents a convenient determination method for carbaryl in polluted water by micellar-stabilized room temperature phosphorescence with Na(2)SO(3) as oxygen scavenger. The effect of various experimental conditions on the determination of carbaryl is discussed in detail. The analytical curve of carbaryl gives a linear dynamic range of 2 x 10(-7)-6 x 10(-5) mol/l., and a detection limit of 2 x 10(-7) mol/l. A recovery of 90-100% was obtained for 0.05-0.1 ppm carbaryl.     

Flow-injection chemiluminometric determination of some thioxanthene derivatives in pharmaceutical formulations and biological fluids using the [Ru(dipy)3(2+)]-Ce(IV) system.

A flow-injection (FI) methodology using tris(2,2'-dipyridyl)ruthenium(II), [Ru(dipy)3(2+)], chemiluminescence (CL) was developed for the rapid and sensitive determination of three thioxanthene derivatives, namely zuclopenthixol hydrochloride, flupentixol hydrochloride and thiothixene. The method is based on the CL reaction of the studied thioxanthenes with [Ru(dipy)3(2+)] and Ce(IV) in a sulfuric acid medium. Under the optimum conditions, calibration graphs were obtained over the concentration ranges 0.002-6 migrograms/ml for zuclopenthixol hydrochloride, 0.5-15 micrograms/ml for flupentixol hydrochloride and 0.05-7.5 micrograms/ml for thiothixene. The limits of detection (s/n = 3) were 4.2 x 10(-9) mol/l zuclopenthixol hydrochloride, 2 x 10(-8) mol/l flupentixol hydrochloride and 4.5 x 10(-8) mol/l thiothixene. The method was successfully applied to the determination of these compounds in dosage forms and biological fluids.     

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.     

A fluorescence quenching method for the determination of nitrite with Rhodamine 110

A simple and sensitive fluorescence quenching method for the determination of trace nitrite has been developed. The method is based on the reaction of Rhodamine 110 with nitrite in acidic medium to form a new compound, which has much lower fluorescence. The optimum experimental conditions were studied. The linear range was obtained at a nitrite concentration of 1.0 x 10(-8)-3.0 x 10(-7)mol l(-1) with a detection limit of 7.0 x 10(-10) mol l(-1) (S/N=3). The proposed method has been successfully applied to the determination of nitrite in tap water and lake water without extraction.     

Spectrophotometric determination of fluoxetine by batch and flow injection methods

A rapid, simple, and accurate spectrophotometric method is presented for the determination of fluoxetine by batch and flow injection analysis methods. The method is based on fluoxetine competitive complexation reaction with phenolphthalein-beta-cyclodextrin (PHP-beta-CD) inclusion complex. The increase in the absorbance of the solution at 554 nm by the addition of fluoxetine was measured. The formation constant for fluoxetin-beta-CD was calculated by non-linear least squares fitting. Fluoxetine can be determined in the range 7.0 x 10(-6)-2.4 x 10(-4) mol l(-1) and 5.0 x 10(-5)-1.0 x 10(-2) mol l(-1) by batch and flow methods, respectively. The limit of detection and limit of quantification were respectively 4.13 x 10(-6) mol l(-1) and 1.38 x 10(-5) mol l(-1) for batch and 2.46 x 10(-5) mol l(-1) and 8.22 x 10(-5) mol l(-1) for flow method. The sampling rate in flow injection analysis method was 80+/-5 samples h(-1). The method was applied to the determination of fluoxetine in pharmaceutical formulations and after addition to human urine samples.     

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.     

Chemiluminescence determination of sulfite in sugar and sulfur dioxide in air using Tris(2,2'-bipyridyl)ruthenium(II)-permanganate system

A chemiluminescence (CL) detection for the determination of sulfite using the reaction of Ru(bipy)(3)(2+) (bipy=2,2'-bipyridyl) -SO(3)(2-)-KMnO(4) is described. The concentration of sulfite is proportional to the CL intensity from 5.0x10(-8) to 1.25x10(-4) mol l(-1). The limit of detection is 2.5x10(-8) mol l(-1) and the relative standard deviation is 4.9% for the 2x10(-5) mol l(-1) sulfite solution in six repeated measurements. This method has been successfully applied to the determination of sulfite in sugar and sulfur dioxide in air by using triethanolamine (TEA) as the absorbent material.     

A tripod ligand as new sensitiser for the enzyme amplified lanthanide luminescence determination of esterase

Screening of a small library of tripod ligands resulted in the discovery of bis(2-pyridylmethyl)-(2-hydroxybenzyl)amine (HL1) as a new sensitiser, which is able to transfer its excitation energy to terbium(III). After synthesis of the acetic acid ester of HL1, a highly selective method for the determination of porcine liver esterase by means of enzyme amplified lanthanide luminescence (EALL) was developed. Enzyme-catalysed cleavage of the ester results in the formation of HL1. After excitation at 297 nm, the characteristic emission of Tb(III) at 545 nm is observed and used to determine the esterase concentration. In contrast to existing EALL methods, this method may be carried out at neutral pH and without further additives. Limit of detection for porcine liver esterase is 10(-9) mol l(-1) and limit of quantification is 3 x 10(-9) mol l(-1). A linear calibration range of two decades starting at the limit of quantification is observed.     

Permanganate-based chemiluminescence analysis of ferulic acid using flow injection.

A simple, sensitive and rapid flow-injection chemiluminescence method has been developed for the determination of ferulic acid based on the chemiluminescence reaction of ferulic acid with potassium permanganate in a nitric acid medium. A strong chemiluminescence signal was observed when ferulic acid was injected into an acidic potassium permanganate solution in a flow-cell. The present method allowed the determination of ferulic acid in the concentration range of 6.0 x 10(-6) to 2.0 x 10(-4) mol l(-1); the detection limit (3sigma) for ferulic acid was 9.6 x 10(-8) mol l(-1). The relative standard deviation was 1.0% for 11 replicate analyses of 2.0 x 10(-4) mol l(-1) ferulic acid. The proposed method was applied to the determination of ferulic acid in real samples with satisfactory results. Moreover, the reaction mechanism of the chemiluminescence system was primarily considered.     

Determination of morphine in process streams by sequential injection analysis with chemiluminescence detection

A procedure for the determination of morphine in process streams by sequential injection analysis based on the chemiluminescence reaction of morphine with acidic potassium permanganate in the presence of sodium hexametaphosphate is presented. The chemiluminescence emission has been monitored using an in-house detection system which consisted of a fibre optic flowthrough cell and a sensitive, low dark current, photomultiplier tube. The calibration graph (range 2 x 10(-8) to 1 x 10(-4) mol/l) was not linear over the entire range of concentration, with a polynomial equation of best fit of y = 1.0 x 10(15) x(3) - 2.2 x 10(11) x(2) + 1.3 x 10(7) x - 8.3. The calibration function approximates linearity over the concentration range 2.5 x 10(-6) to 3.0 x 10(-5) mol/l where the slope of the log-log plot is 1.09 +/- 0.16. The detection limit was estimated at about 10(-8) mol/l from the response of the lowest calibration standard (2.5 x 10(-8) mol/l) which gave a signal to noise ratio of 3 : 1. Although the structurally related codeine did not interfere significantly the results suggest that this method may be susceptible to matrix effects, dependent on the location of sampling from the process stream.