Chemiluminescence determination of fluoroquinolone antibiotics using a soluble manganese (IV)-sulphite system.

The reaction of soluble manganese (IV) with sulphite in acidic condition was found to elicit weak chemiluminescence (CL). The CL signal was remarkably enhanced in the presence of three fluoroquinolones, viz. norfloxacin, ofloxacin and ciprofloxacin. Based on these observations, a new flow-injection CL method was developed for the determination of these fluoroquinolones. The method allows determination in the range 5.0 x 10(-8)-1.0 x 10(-6) mol/L for norfloxacin, 1.0 x 10(-7)-8.0 x 10(-6) mol/L for ofloxacin and 1.0 x 10(-7)-3.0 x 10(-5) mol/L for ciprofloxacin, with detection limits of 3 x 10(-8) mol/L, 5 x 10(-8) mol/L and 3 x 10(-8) mol/L, respectively. The method was applied to the determination of fluoroquinolones in pharmaceutical preparations.     

Study of the catalytic effect of PAR on the luminol-potassium ferricyanide reaction using a flow-injection chemiluminescence method.

We discovered that 4-(2-pyridylazo) resorcinol (PAR) has a strong catalytic effect on luminol-potassium ferricyanide chemiluminescence (CL). Results indicated that the chemiluminescence intensities at maximum light emission were linearly corrected with the concentration of PAR over the range 1.0 x 10(-5)-1.0 x 10(-7) mol/L. A detection limit of 5.7 x 10(-8) mol/L for PAR was achieved. It was found that some metal ions strongly affected this catalytic reaction. Based on this finding, the luminol-potassium ferricyanide-PAR reaction was developed for the determination of metal ions. The detection limits (S/N = 3) for Ni2+, Cr3+, Zn2+, Co2+ and Mn2+ were determined to be 1.0 x 10(-9) mol/L, 5.0 x 10(-9) mol/L, 5.0 x 10(-8) mol/L, 1.0 x 10(-9) mol/L and 1.0 x 10(-8) mol/L, respectively. In addition, the relative standard deviation values for these metal ion assays were in the range 0.82-2.72% (n = 6).     

Determination of tetracycline, chlortetracycline and oxytetracycline by flow injection with inhibitory chemiluminescence detection using copper(II) as a probe ion.

This paper reports an indirect flow-injection (FI) method for the determination of the tetracycline drugs (TCs), tetracycline (TC), chlortetracycline (CTC) and oxytetracycline (OTC), using copper(II) as a probe ion. The method was based on the inhibition caused by these TCs to the copper(II)-catalysed chemiluminescence (CL) reaction between luminol and H(2)O(2). The CL reaction was induced on-line and injection of the sample produced negative peaks as a result of the copper(II) complexation or displacement by the analytes. The height of the peaks was proportional to the drug concentration in the sample. The choice of the catalyst ion, the concentration of luminol, H(2)O(2) and copper(II) are discussed. The linear range was 3.6 x 10(-8)-1.0 x 10(-5), 1.1 x 10(-7)-1.0 x 10(-5) and 1.9 x 10(-7)-1.0 x 10(-5) mol/L for TC, CTC and OTC, respectively. The detection limit was 5.0 x 10(-9) mol/L for TC, 1.0 x 10(-8) mol/L for CTC and 2.0 x 10(-8) mol/L for OTC (3sigma), respectively. The method was applied to the determination of TCs in pharmaceutical preparations and human urine with recoveries in the range 95-105%.     

Determination of bisphenol A using a flow injection inhibitory chemiluminescence method.

A new flow injection chemiluminescence (CL) method has been developed for the determination of bisphenol A (BPA), based on the inhibitory effect of BPA on the chemiluminescence reaction between luminol and potassium hexacyanoferrate. Under optimum conditions, the decrease in CL emission intensity was linear with BPA concentration in the range 8.0 x 10(-7)-1.2 x 10(-5) mol/L, and the detection limit was 3.1 x 10(-7) mol/L. The relative standard deviation (RSD) of 11 replicate measurements was 2.6% for 2.0 x 10(-6) mol/L BPA (n = 11). The sampling frequency was calculated to be ca. 120/h. This method has been successfully used to determine the content of BPA in aqueous solution of polycarbonate materials. A brief discussion on the possible chemiluminescence reaction mechanism is presented.     

Flow-injection chemiluminescence determination of catecholamines based on their enhancing effects on the luminol-potassium periodate system.

A rapid and sensitive chemiluminescence (CL) method using flow injection analysis is described for the determination of four catecholamines, dopamine, adrenaline, isoprenaline and noradrenaline, based on their greatly enhancing effects on the CL reaction of luminol-potassium periodate in basic solutions. The optimized chemical conditions for the chemiluminescence reaction were 1.0 x 10(-4) mol/L luminol and 1.0 x 10(-5) mol/L potassium periodate in 0.2 mol/L sodium hydroxide (NaOH). Under the optimized conditions, the calibration graphs relating the CL signal intensity (peak height) to the concentration of the analytes were curvilinear and they were suitable for determining dopamine, adrenaline, isoprenaline, and noradrenaline in the range 0.1-10 ng/mL, 0.1-100 ng/mL, 1-100 ng/mL and 5-50 ng/mL, respectively, with the relative standard deviations of 0.8-1.7%. The detection limits of the method are 0.02 ng/mL for dopamine, 0.01 ng/mL for adrenaline, 0.1 ng/mL for isoprenaline and 2.0 ng/mL for noradrenaline. The sampling frequency was calculated to be about 60/h. The selectivity of the method was good, because a series of common ions or excipients, such as K(+), Ba(2+), CO(3)(2-), NO(3)(-), SO(4)(2-), PO(4)(3-), sodium citrate, sodium bisulphite, oxidate dopamine, starch, lactose, carbamide and gelatin, could not produce interference when their concentrations were 1000-fold than those of dopamine. The present method was successfully applied to the determination of the four catecholamines in pharmaceutical injections.     

Chemiluminescence of synephrine based on the cerium(IV)-rhodamine B system.

A new chemiluminescence (CL) method is described for the determination of synephrine. It is based on the reaction between synephrine and Ce(IV) in a nitric acid medium and measurement of the CL intensity produced by rhodamine B used as a luminophore, similar to luminol or lucigenin in basic media, instead of as a sensitizer. In the optimum conditions, the increase of CL intensity was correlated with synephrine concentration over the range 5.0 x 10(-9)-1.0 x 10(-6) g/mL with a detection limit of 1.0 x 10(-9) g/mL. The relative standard deviation (RSD) was 2.9% for 1.0 x 10(-7) g/mL synephrine (n = 11). The method was applied to the determination of a drug in herbal products, citrus fruit and biological samples, with satisfactory results. The results given by the proposed method are in good agreement with those given by HPLC-UV and UV spectrophotometry.     

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.     

An assay for inorganic mercury(II) based on its post-catalytic enhancement effect on the potassium permanganate-luminol system.

A strong chemiluminescence (CL) response is observed when potassium permanganate solution is injected into basic luminol solution. When the CL reaction terminates, subsequent injection of Hg2+ solution into the reaction mixture results in a new CL reaction. Based on the post-catalytic enhancement effect of Hg2+ on the potassium permanganate-luminol system in basic media, a fast and simple CL-coupled flow injection analysis for the determination of Hg2+ was developed. In optimum conditions, CL intensity is proportional to Hg2+ concentration over the range 1.0 x 10(-8)-1.0 x 10(-5) g/mL, with a detection limit of 2.0 x 10(-9) g/mL. The relative standard deviation (RSD) is 3.6% for 1.0 x 10(-7) g/mL Hg2+ (n = 11). After pretreatment with sulphydryl cotton fibre, environmental water samples were analysed by the proposed method for total mercury determination with satisfactory results. The results were in good agreement with those given by hydride generation-cold vapour atomic absorption spectrometry (HG-CVAAS).     

High-sensitive determination of coenzyme Q(10) in iodinate-beta-cyclodextrin medium by inclusion reaction and catalytic polarography

A novel polarographic method for the determination of coenzyme Q(10) in beta-cyclodextrin (beta-CD) and iodinate system is proposed. The stability of coenzyme Q(10) to light was improved by the formation of coenzyme Q(10)-beta-CD inclusion complex. In addition, the sensitivity for the determination of coenzyme Q(10) was enhanced by both the formation and the polarographic catalytic wave of the inclusion complex in the presence of iodinate. In 0.1 mol/L HAc-NaAc (pH 4.7)-5.0 x 10(-5) mol/L beta-CD-1.2 x 10(-3) mol/L potassium iodinate-ethanol/water (60:40, v/v) medium, coenzyme Q(10)-beta-CD inclusion complex yielded a sensitive association/parallel catalytic wave. The second-order derivative peak current of the catalytic wave was proportional to coenzyme Q(10) concentration in the range of 6.0 x 10(-8)-2.5 x 10(-7) mol/L, and the detection limit was 1.0 x 10(-8) mol/L. The proposed method has high analytical sensitivity and is allowed to determine coenzyme Q(10) under light.     

Flow-injection electrogenerated chemiluminescence determination of fluoroquinolones based on its sensitizing effect.

A simple and sensitive flow-injection electrogenerated chemiluminescence (ECL) method for the determination of fluoroquinolones was developed. The method is based on the sensitizing effect of fluoroquinolones on the weak ECL signal of electrochemical oxidation of luminol on the surface of the platinum flake electrode in the medium of 0.1 mol/L Na2CO3-NaHCO3. At the optimum experimental conditions, the relative ECL intensity increased linearly with increasing fluoroquinolones concentration, in the ranges 1.0 x 10(-8)-2.0 x 10(-4) g/mL for norfloxacin, 5.0 x 10(-9)-6.0 x 10(-6) g/mL for oxfloxacin, 2.0 x 10(-8)-1.4 x 10(-5) g/mL for ciprofloxacin, 1.0 x 10(-8)-1.4 x 10(-5) g/mL for pefloxacin, and 1.0 x 10(-9)-1.0 x 10(-5) g/mL for enoxacin, with detection limits of 4.0 x 10(-9) g/mL, 2.0 x 10(-9) g/mL, 1.0 x 10(-8) g/mL, 8.0 x 10(-9) g/mL, and 8.0 x 10(-10) g/mL, respectively. The relative standard deviations were all less than 2.5% for the determination of 2.0 x 10(-6) g/mL fluoroquinolones (n = 11). The method was used to determine these medicines in pharmaceutical samples with satisfactory results.     

Post‐chemiluminescence determination of chloramphenicol based on luminol–potassium periodate system

A post‐chemiluminescence (PCL) phenomenon was observed when chloramphenicol was injected into a mixture of luminol and potassium periodate after the chemiluminescence (CL) reaction of luminol–potassium periodate had finished. The possible reaction mechanism was proposed based on studies of the CL kinetic characteristics, the CL spectra, the fluorescence spectra and the UV‐vis absorption spectra of the related substances. Based on the PCL reaction, a rapid and sensitive method for the determination of chloramphenicol was established. The linear response range was 6.0 × 10^?7–1.0 × 10^?5 mol/L, with a correlation coefficient of 0.9986. The relative standard deviation (RSD) for 5.0 × 10^?6 mol/L chloramphenicol was 2.3% (n = 11). The detection limit was 1.6 × 10^?7 mol/L. The method has been applied to the determination of chloramphenicol in pharmaceutical samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrochemical behaviors of diethylstilbestrol and its application in pharmacokinetics

The electrochemical behaviors of diethylstilbestrol (DES) at a glassy carbon electrode were investigated by cyclic voltammetry, linear sweep voltammetry, and differential pulse voltammetry (DPV). Based on these, a sensitive and selective DPV method was developed for determination of DES. The linear response range of DES is 1.0 x 10(-4)-2.0 x 10(-6) mol/L and the detection limit was 8.0 x 10(-8) mol/L. The developed method has been used for the pharmacokinetics of DES in rabbit blood plasma.     

Sensitive determination of 2‐methoxyestradiol in pharmaceutical preparations and serum samples using flow injection chemiluminescence

A rapid and sensitive flow injection chemiluminescence (FI–CL) method is described for the determination of 2‐methoxyestradiol (2ME) based on enhancement of the CL intensity from a potassium ferricyanide–calcein system in sodium hydroxide medium. The optimum conditions for the CL emission were investigated. Under optimized conditions, a linear calibration graph was obtained over the range 1.0 × 10^‐8 to 1.0 × 10^‐6 mol/L (r = 0.998) 2ME with a detection limit (3σ) of 5.4 × 10^‐9 mol/L. The relative standard deviation (RSD) for 5.0 × 10^‐7 mol/L 2ME was 1.7%. As a preliminary application, the proposed method was successfully applied to the determination of 2ME in injection solutions and serum samples. The possible CL mechanism was also proposed. Copyright © 2013 John Wiley & Sons, Ltd.     

A new sensitive flow-injection chemiluminescence method for the determination of H(2)-receptor antagonists.

Based on the chemiluminescence (CL) intensity generated from the potassium ferricyanide [K(3)Fe(CN)(6)]-rhodamine 6G system in sodium hydroxide (NaOH) medium, a new sensitive flow-injection chemiluminescence (FI-CL) method has been developed, validated and applied for the determination of three kinds of H(2)-receptor antagonists: cimetidine (CIMT), ranitidine (RANT) hydrochloride and famotidine (FAMT). Under the optimum conditions, the linear range for the determination was 1.0 x 10(-9)-7.0 x 10(-5) g/ml for CIMT, 1.0 x 10(-9)-5.0 x 10(-5) g/mL for RANT hydrochloride and 5.0 x 10(-9)-7.0 x 10(-5) g/mL for FAMT. During 11 repeated measurements of 1.0 x 10(-6) g/mL sample solutions, the relative standard deviations (RSDs) were all <5%. The detection limit was 8.56 x 10(-10) g/mL for CIMT, 8.69 x 10(-10) g/mL for RANT hydrochloride and 2.35 x 10(-9) g/mL for FAMT (S:N = 3). This method has been successfully implemented for the analysis of H(2)-receptor antagonists in pharmaceuticals.     

A novel chemiluminescence system for the determination of daidzein and its hydroxyl radical-scavenging capacity

A novel chemiluminescence (CL) system was established for the determinations of daidzein in pharmaceutical preparations and to assess its ability to scavenge hydroxyl radicals. It was shown that a strong CL signal generated when eosin Y was mixed with Fenton reagent was decreased significantly when daidzein was added to the reaction system due to partial scavenging of the hydroxyl radicals in the solution. The extent of decrease in the CL intensity had a good stoichiometric relationship with the daidzein concentration. Based on this, we developed a new method for the determination of daidzein, using a flow‐injection chemiluminescence (FI–CL) technique. Under the optimal conditions, the linear range of daidzein concentration was 8.0 × 10^–8–3.0 × 10^–6 mol/L (R = 0.9982), with a detection limit of 9.0 × 10^–9 mol/L (S:N = 3), and the RSD was 5.8% for 1.0 × 10^–6 mol/L daidzein (n = 11). This method was successfully used in the determination of daidzein in tablets and for evaluation of the hydroxyl radical‐scavenging capacity of daidzein. The possible reaction mechanism of the CL system is discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Spectrofluorimetric determination of dopamine using 1,5-bis(4,6-dicholro-1,3,5-triazinylamino) naphthalene.

A new fluorescent reagent, 1,5-bis(4,6-dichloro-1,3,5-triazinylamino)naphthalene, containing two active chlorines, was synthesized by a one-step reaction. Under the optimum conditions for the determination of dopamine, the enhanced fluorescence intensity is proportional to the dopamine concentration. The fluorescence intensity was measured at lambda(ex/em) = 400/460 nm, with and without dopamine. The linear range and detection limit for the determination of dopamine were 1.0 x 10(-7) mol/L-5.0 x 10(-5) mol/L and 4.0 x 10(-8) mol/L. This method is simple, practical, can afford good precision and accuracy and can be successfully applied to assess dopamine in injections and human serum samples.     

Flow injection spectrophotometric determination of the antibiotic fosfomycin in pharmaceutical products and urine samples after on-line thermal-induced digestion

A new flow injection (FI) method for the precise and rapid spectrophotometric determination of the antibiotic fosfomycin (FMC) in urine and pharmaceutical samples is described. The method is based on the on-line quantitative thermal-induced digestion of the analyte prior to injection into the FI system. Ammonium persulfate was used as the oxidation reagent. The resulting orthophosphate ions were determined spectrophotometrically (lambda(max) = 690 nm) using the molybdenum blue approach. Chemical and FI variables that affected on-line oxidation were studied and optimized. The proposed method is very precise (s(r) = 1.2% at 1.0 x 10(-4) mol L(-1) FMC, n = 12), offers a high sampling rate of 60 h(-1), and allows for the determination of the analyte in the range 3.0 x 10(-6) to 3.0 x 10(-4) mol L(-1) with a satisfactory 3sigma detection limit of 1.0 x 10(-6) mol L(-1). Application of the proposed method to urine and pharmaceutical samples yielded accurate results with percentage recoveries in the range 96.4-102.5%.     

Spectrofluorimetric determination of 5-hydroxytryptamine using chlorosulphonylthenoyltrifluoroacetone-europium probe.

A new spectrofluorimetric method was developed for the determination of trace amounts of 5-hydroxytryptamine (5-HT). Using chlorosulphonylthenoyltrifluoroacetone (CTTA)-europium (Eu(3+)) ion as a fluorescent probe in a buffer solution at pH 11.0, 5-HT can remarkably enhance the fluorescence intensity of the CTTA-Eu(3+) complex at lambda = 612 nm; the enhanced fluorescence intensity of Eu(3+) is proportional to the concentration of 5-HT. Optimum conditions for the determination of 5-HT were also investigated. The linear range and detection limit for the determination of 5-HT were 1.0 x 10(-7)-1.2 x 10(-5) mol/L and 8.5 x 10(-8) mol/L, respectively. This method is simple, practical and relatively free of interference from coexisting substances, and can be applied to assess 5-HT in urine samples.     

DPPH·–luminol chemiluminescence system and its application in the determination of scutellarin in pharmaceutical injections and rat plasma with flow injection analysis

In this article, a DPPH·–luminol chemiluminescence (CL) system was reported and the CL mechanism was discussed according to the CL kinetic properties after sequence injecting DPPH· into the DPPH·–luminol reaction mixture. It was observed that scutellarin could inhibit the CL response of the DPPH·–luminol system. Based on this observation, a simple and rapid flow injection CL method was developed for the determination of scutellarin using the inhibition effect in alkaline medium. The optimized chemical conditions for the CL reaction were 5 × 10^?6 mol/L DPPH · and 1.0 × 10^?4 mol/L luminol in 0.01 mol/L NaOH. Under optimized conditions, the CL intensity was inversely proportional to the concentration of scutellarin over the ranges 5–2000 and 40–3200 ng/ml in pharmaceutical injection and rat plasma, respectively. The limits of detection (S/N  = 3) were 5 and 40 ng/ml in preparations and rat plasma, respectively. Furthermore, the precision, recovery and stability of the validated method were acceptable for the determination of scutellarin in both pharmaceutical injections and rat plasma. The presented method was successfully applied in the determination of scutellarin in pharmaceutical injections and real rat plasma samples.     

Flow injection chemiluminescence determination of isoniazid using the lucigenin-periodate system.

A weak chemiluminescence (CL) signal was observed during the mixing of isoniazid with lucigenin in alkaline aqueous solution. The CL signal was enhanced more than 100 times in the presence of potassium periodate. This CL system was developed for the determination of isoniazid using a flow injection mode. The CL intensity is proportional to the concentration of isoniazid in the range 0.005-1.0 mg/L. The limit of detection is 0.0034 mg/L and the relative standard deviation is 2.0% for 0.2 mg/L isoniazid solution in 11 repeated measurements. The method was applied to the determination of isoniazid in pharmaceutical preparations and satisfactory results were obtained.