A highly efficient and selective turn‐on fluorescent sensor for Hg2+, Ag+ and Ag nanoparticles based on a coumarin dithioate derivative

Based on chelation‐enhanced fluorescence, a new fluorescent coumarin derivative probe 3(1‐(7‐hydroxy‐4‐methylcoumarin)ethylidene)hydrazinecarbodithioate for Hg²⁺, Ag⁺ and Ag nanoparticles is reported. Fluorescent probe acts as a rapid and highly selective “off–on” fluorescent probe and fluorescence enhancement by factors 5 to12 times was observed upon selective complexation with Hg²⁺, Ag⁺ and Ag nanoparticles. The molar ratio plots indicated the formation of 1:1 complexes between Hg²⁺ and Ag⁺ with the probe. The linear response range covers a concentration range 0.1 × 10^–5–1.9 × 10^–5 mol/L, 0.1 × 10^–5–2.3 × 10^–5 mol/L and 0.146 × 10^–12–2.63 × 10^–12 mol/L for Hg²⁺, Ag⁺ and Ag nanoparticles, respectively. The interference effect of some anions and cations was also tested. Copyright © 2013 John Wiley & Sons, Ltd.     

Enhanced electrochemiluminescence of Ru(bpy)32+ by flavone compounds

Flavones such as morin, rutin, quercitrin, quercetin and wogonin were found to be able to strongly enhance the electrochemiluminescence (ECL) of the Ru(bpy)₃²⁺ system. Based on this, a novel ECL method with good stability and reproducibility could be developed for determination of flavones. Under the optimum conditions, the enhanced ECL intensity was linear with the flavones concentration in a wide range. The detection limits (defined as S:N = 3) for morin, rutin, quercitrin, quercetin and wogonin were 3.2 × 10^–7 mol/L, 4.3 × 10^–7, 1.8 × 10^–7, 8.0 × 10^–8 and 1.0 × 10^–7 mol/L, respectively. In addition, the possible mechanism for the Ru(bpy)₃²⁺ ECL system in the presence of flavones is also discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Determination of free cholesterol based on a novel flow‐injection chemiluminescence method by immobilizing enzyme

A novel flow injection chemiluminescence method is proposed for determination of cholesterol in this paper. The cholesterol oxidase was immobilized onto sol–gel and prepared as an enzymatic reaction column. The determination of cholesterol was performed by quantitative determination of hydrogen peroxide produced from an enzymatic reaction. The luminol–H₂O₂–metal chelate diperiodatocuprate(III) system ensured that the method was highly sensitive and selective. Free cholesterol was determined over the range 5.0 × 10^–8 mol/L–5.0 × 10^–7 mol/L, with a limit of detection (3σ) of 1.9 × 10^–8 mol/L. The relative standard deviation (RSD) for 2.5 × 10^–7 mol/L was 2.7% (n = 7). The proposed method offered the advantages of sensitivity, selectivity, simplicity and rapidity for free cholesterol determination, and was successfully applied to the direct determination of free cholesterol in serum. Copyright © 2008 John Wiley & Sons, Ltd.     

Highly sensitive spectrofluorimetic determination of rutin based on its activated effect on a multi‐enzyme redox system

A highly sensitive and simple spectrofluorimetric method for the determination of rutin, based on its activated effect on a haemoglobin‐catalysed reaction, was developed. Under optimum conditions, the concentration of rutin was linear, with decreased fluorescence (ΔF) of the system under optimal experimental conditions. The calibration graph was linear in the range 1.0 × 10^–7–3.0 × 10^–5 mol/L, with a detection limit of 7.0 × 10^–8 mol/L. The relative standard deviation (RSD) was 3.26% for 11 determinations of 1.0 × 10^–5 mol/L. This method was used for the determination of rutin in pharmaceuticals with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.     

Selective recognition of acetate ion based on fluorescence enhancement chemosensor

Fluorescence study of the complexation between uranyl salophen (L) and some common anions in acetonitrile–water (90:10, v/v) solution showed a tendency of L toward acetate ion (AcO^?). The fluorescence enhancement of L is attributed to a 1:1 complex formation between L and acetate ion which was utilized as the basis for the selective detection of AcO^?. The association constant of the 1:1 complex formation of L–AcO^? was calculated as 6.60 × 10⁶. The linear response range of the fluorescent chemosensor covers a AcO^? concentration range of 1.6 × 10^?7 to 2.5 × 10^?5 mol/L, with a detection limit of 2.5 × 10^?8 mol/L. L showed a selective and sensitive fluorescence enhancement response toward acetate ion over I₃^?, NO₃^?, CN^?, CO₃^2?, Br^?, Cl^?, F^?, H₂PO4^? and SO₄^2?, which was attributed to the higher stability of inorganic complex between acetate and L. Copyright © 2012 John Wiley & Sons, Ltd.     

A highly selective fluorescent probe for pyrophosphate detection in aqueous solutions

A novel and simple fluorescence enhancement method is introduced for selective pyrophosphate (PPi) sensing in an aqueous solution. The method is based on a 1:1 metal complex formation between tris(8‐hydroxyquinoline‐5‐sulphonate) thulium(III) [Tm(QS)₃] and PPi ion. The linear response covers a concentration range of 1.6 × 10^?7–1.0 × 10^?5 mol/L PPi and the detection limit is 2.3 × 10^?8 mol/L. The association constant of Tm(QS)₃–PPi complex was calculated as 2.6 × 10⁵ mol/L. Tm(QS)₃ shows a selective and sensitive fluorescence enhancement toward PPi ion in comparion with I₃^?, NO₃^?, CN^?, CO₃^2?, Br^?, Cl^?, F^?, H₂PO₄^? and SO₄^2?, which is attributed to higher stability of the inorganic complex between pyrophosphate ion and Tm(QS)₃. Copyright © 2011 John Wiley & Sons, Ltd.     

Cupric oxide nanoparticles‐enhanced chemiluminescence method for measurement of β‐lactam antibiotics

A simple, sensitive cupric oxide nanoparticles (CuO NPs) enhanced chemiluminescence (CL) method was developed for the measurement of β‐lactam antibiotics, including amoxicillin and cefazolin sodium. The method was based on suppression of the CuO NPs–luminol–H₂O₂ CL reaction by β‐lactam antibiotics. Experimental parameters that influenced the inhibitory effect of the antibiotic drugs on the CL system, such as NaOH (mol/L), luminol (µmol/L), H₂O₂ (mol/L) and CuO NPs (mg/L) concentrations, were optimized. Calibration graphs were linear and had dynamic ranges of 1.0 × 10^–6 to 8.0 × 10^–6 mol/L and 3.0 × 10^–5 to 5.0 × 10^–3 mol/L for amoxicillin and cefazolin sodium, respectively, with corresponding detection limits of 7.9 × 10^–7 mol/L and 1.8 × 10^–5 mol/L. The relative standard deviations of five replicate measurements of 5.0 × 10^–6 amoxicillin and 5 × 10^–4 cefazolin sodium were 5.43 and 5.01%, respectively. The synthesized CuO NPs were characterized by X‐ray diffraction (XRD) and transmission electronmicroscopy (TEM). The developed approach was exploited successfully to measure antibiotics in pharmaceutical preparations. Copyright © 2014 John Wiley & Sons, Ltd.     

Rapid determination of gatifloxacin in biological samples and pharmaceutical products using europium‐sensitized fluorescence spectrophotometry

A europium‐sensitized fluorescence spectrophotometry method using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was developed for the determination of gatifloxacin (GFLX). The GFLX–Eu³⁺–SDBS system was studied and it was found that SDBS significantly enhanced the fluorescence intensity of the GFLX–Eu³⁺ complex (about 25‐fold). The optimal experimental conditions were determined as follows: excitation and emission wavelengths of 338 and 617 nm, pH 7.5, 3.0 × 10^–6 mol/L europium(III), and 5.0 × 10^–5 mol/L SDBS. The enhanced fluorescence intensity of the system (ΔI_f) showed a good linear relationship with the concentration of GFLX over the range 1.0 × 10^–8–8.0 × 10^–7 mol/L with a correlation coefficient of 0.9990. The detection limit (S:N = 3) was determined as 1.0 × 10^–9 mol/L. This method has been successfully applied for the determination of GFLX in pharmaceuticals and human urine/serum samples. Compared with most other methods reported, the rapid and simple procedure proposed here offered higher sensitivity, wider linear range and good stability. The luminescence mechanism of the system is also discussed in detail. Copyright © 2008 John Wiley & Sons, Ltd.     

Flow‐injection determination of cysteine in pharmaceuticals based on luminol–persulphate chemiluminescence detection

A flow injection (FI) method is reported for the determination of l‐ cysteine, based on its enhancement on chemiluminescence (CL) emission of luminol oxidized by sodium persulphate in alkaline solution. The calibration graph was linear over the range 1.0 × 10^–9–5.0 × 10^–7 mol/L (r² = 0.9992), with relative standard deviations (RSDs) in the range 1.1–2.3% (n = 4). The limit of detection (3σ blank) was 5.0 × 10^–10 mol/L with a sample throughput of 120/h. The method was applied to pharmaceuticals and the results obtained were in reasonable agreement with the amount labelled. The proposed method was also applied to cysteine in synthetic amino acid mixtures. Calibration graphs of N‐acetylcysteine and glutathione over the range 1.0–50 × 10^–8 and 0.5–7.5 × 10^–7 mol/L were also established (r² = 0.998 and 0.9986) with RSDs in the range 1.0–2.0% (n = 4), and the limits of detection (3σ blank) were 5.0 × 10^–9 and 1.0 × 10^–8 mol/L, respectively. Copyright © 2008 John Wiley & Sons, Ltd.     

Flow injection analysis of thiamazole based on strong Ru(bpy)32+ co‐reactant electrochemiluminescence

Based on the strong electrochemiluminescence (ECL) reaction between thiamazole and tris(2,2′‐bipyridine)ruthenium(II) (Ru(bpy)₃²⁺), a sensitive, simple and rapid flow injection analysis method for the determination of thiamazole was developed. When a Pt working electrode was maintained at a potential of +1.50 V (vs Ag/AgCl) in pH 12.0 H₃PO₄–NaOH solution containing thiamazole and Ru(bpy)₃²⁺ at a flow rate of 1.0 mL/min, a linear range of 2.0 × 10⁻⁷–1.0 × 10⁻⁴ mol/L with a detection limit of 5.0 × 10⁻⁸ mol/L was obtained for the detection of thiamazole. The method showed good reproducibility with a relative standard deviation (RSD) of 0.75%. The method has been successfully applied to the determination of thiamazole in spiked animal feeds. In addition, a co‐reactant ECL mechanism was proposed for the thiamazole–Ru(bpy)₃²⁺ system. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrophoresis–chemiluminescence detection of phenols catalyzed by hemin

Based on the catalytic activity of hemin, an efficient biocatalyst, an indirect capillary electrophoresis–chemiluminescence (CE‐CL) detection method for phenols using a hemin–luminol–hydrogen peroxide system was developed. Through a series of static injection experiments, hemin was found to perform best in a neutral solution rather than an acidic or alkaline medium. Although halide ions such as Br^? and F^? could further enhance the CL signal catalyzed by hemin, it is difficult to apply these conditions to this CE‐CL detection system because of the self‐polymerization of hemin, as it hinders the CE process. The addition of concentrated ammonium hydroxide to an aqueous/dimethyl sulfoxide solution of hemin–luminol afforded a stable CE‐CL baseline. The indirect CE‐CL detection of five phenols using this method gave the following limits of detections: 4.8 × 10^?8 mol/L (o‐sec‐butylphenol), 4.9 × 10^?8 mol/L (o‐cresol), 5.4 × 10^?8 mol/L (m‐cresol), 5.3 × 10^?8 mol/L (2,4‐dichlorophenol) and 7.1 × 10^?8 mol/L (phenol). Copyright © 2013 John Wiley & Sons, Ltd.     

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.     

Investigation on the co‐luminescence effect of europium (III)–lanthanum(III)–dopamine–sodium dodecylbenzene sulfonate system and its application

A novel luminescence, enhancement phenomenon in the europium(III)–dopamine–sodium dodecylbenzene sulfonate system was observed when lanthanum(III) was added. Based on this, a sensitive co‐luminescence method was established for the determination of dopamine. The luminescence signal for the europium (III)–lanthanum(III)–dopamine–sodium dodecylbenzene sulfonate system was monitored at λ_ex = 300 nm, λ_em =618 nm and pH 8.3. Under optimized conditions, the enhanced luminescence signal responded linearly to the concentration of dopamine in the range 1.0 × 10^–10–5.0 × 10^–7 mol/L with a correlation coefficient of 0.9993 (n = 11). The detection limit (3σ) was 2.7 × 10^–11 mol/L and the relative standard deviation for 11 parallel measurements of 3.0 × 10^–8 mol/L dopamine was 1.9%. The presented method was successfully applied for the estimation of dopamine in samples of pharmaceutical preparations, human serum and urine. The possible luminescence enhancement mechanism of the system is discussed briefly. Copyright © 2013 John Wiley & Sons, Ltd.     

Chemiluminescence method for the determination of piroxicam by the enhancement of the tris‐(4,7‐diphenyl‐1,10‐phenanthrolinedisulphonic acid) ruthenium(II) (RuBPS)–cerium(IV) system and its application

A simple, rapid chemiluminescence (CL) method was described for the determination of piroxicam, a commonly used analgesic agent drug. A strong CL signal was detected when cerium(IV) sulphate was injected into tris‐(4,7‐diphenyl‐1,10‐phenanthrolinedisulphonic acid) ruthenium(II) (RuBPS)–piroxicam solution. The CL signal was proportional to the concentration of piroxicam in the range 2.8 × 10^–8–1.2 × 10^–5 mol/L. The detection limit was 2 × 10^–8 mol/L and the relative standard deviation (RSD) was 3.7% (c = 7.0 × 10^–7 mol/L piroxicam; n = 11). The proposed method was applied to the determination of piroxicam in pharmaceutical preparations in capsules, spiked serum and urine samples with satisfactory results. Copyright © 2008 John Wiley & Sons, Ltd.     

Highly sensitive spectrofluorimetric determination of trace amounts of prulifloxacin using the aluminium(III)–prulifloxacin system

The fluorescence of the prulifloxacin (PUFX)–Al(III) system was investigated . Experiments indicated that the fluorescence intensity of prulifloxacin could be greatly enhanced by Al(III) and sensitized by sodium dodecylbenzene sulphonate (SDBS). Accordingly, a sensitive spectrofluorimetric method for the determination of prulifloxacin was established. While excited at 275 nm, the enhanced fluorescence intensity at 412 nm of the system (ΔF) showed a good linear relationship with the concentration of prulifloxacin within the range 4.0 × 10^–8–3.0 × 10^–6 mol/L. The regression equation was ΔF = 9.83 + 10.8 × 10⁷c (mol/L); the correlation coefficient and detection limit (3σ/k) were 0.99901 and 2.0 × 10^–8 mol/L, respectively. The proposed method has been successfully applied to determine prulifloxacin in real pharmaceutical samples. The luminescence mechanism of the system is also discussed in detail. Copyright © 2008 John Wiley & Sons, Ltd.     

Development of a sensitive flow‐injection–chemiluminescence detection method for the determination of laevodopa

A simple chemiluminometric method using flow injection has been developed for the determination of laevodopa, based on its sensitizing effect on the weak chemiluminescence (CL) reaction between Na₂SO₃ and acidic KMnO₄. Under optimum experimental conditions, the CL intensity was linearly related to the concentration of laevodopa from 3.4 × 10^–8 to 2.4 × 10^–5 mol/L and the detection limit was 1.1 × 10^–8 mol/L (s:n = 3). The relative standard deviation (RSD) of the proposed method calculated from 20 replicate injection of 3 × 10^–7 mol/L laevodopa was 3.3%. The correlation coefficient was 0.997. The method was successfully applied to the determination of laevodopa in commercial pharmaceutical formulations and spiked urine samples. Copyright © 2008 John Wiley & Sons, Ltd.     

Application of a lanthanide composite nanoparticle‐sensitized luminescence method for the determination of salicylic acid in pharmaceutical formulations and human plasma

Terbium‐acetylacetone (Tb–acac) composite nanoparticles were synthesized using the ultrasonic method. The nanoparticles are water‐soluble, stable and have extremely narrow emission bands and high internal quantum efficiencies. They were used as fluorimetric probes in the determination of salicylic acid (SA), based on the fluorescence enhancement of nanoparticles through fluorescence resonance energy transfer (FRET). The influence of buffer solution was investigated. Under the optimum conditions, a linear calibration graph was obtained over the SA concentration range 5 × 10^–7–1 × 10^–4 mol/L. The limit of detection was found to be 2.5 × 10^–8 mol/L. The relative standard deviation (RSD) for six repeated measurements of 1 × 10^–4 mol/LSA was 1.75%. The method was applied to the determination of SA in pharmaceutical formulations and human plasma. We believe that the proposed approach has great potential for clinical purposes. Copyright © 2008 John Wiley & Sons, Ltd.     

A sensitive method for the determination of levamisole in serum by electrochemiluminescence

A novel method was developed for the determination of levamisole by electrochemiluminescence. The method was based on electrochemiluminescence signal enhancement produced by Ru(bpy)₃²⁺, which reacted with the tertiary amine group of levamisole on a platinum electrode in 12 mmol/L borate buffer (pH 9). A linear relationship between the luminous intensity and concentration of levamisole in the range 0–1 × 10^–7 mol/L was obtained and the detection limit was 1.76 × 10^–11 mol/L. The method is sensitive, selective, simple and convenient. The method has been successfully applied to the analysis of levamisole in serum. Copyright © 2013 John Wiley & Sons, Ltd.     

The determination of glutamine with flow‐injection chemiluminescence detection and mechanism study

The main purpose of this study was to develop an inexpensive, simple, rapid and sensitive chemiluminescence (CL) method for the determination of glutamine (Gln) using a flow‐injection (FI) system. Gln was found to strongly inhibit the CL signal of the luminol–H₂O₂–CuSO₄ system in Na₂B₄O₇ solution. A new FI‐CL method was developed for the determination of Gln. Parameters affecting the reproducibility and CL detection were optimized systematically. Under the optimized conditions, the corresponding linear regression equation was established over the range of 5.0 × 10^?7 to 2.5 × 10^?6 mol/L with the detection limit of 1.8 × 10^?8 mol/L. The relative standard deviation was found to be 1.8% for 11 replicate determinations of 1.5 × 10^?6 mol/L Gln. The proposed method has been satisfactorily applied for the determination of Gln in real samples (Marzulene‐s granules) with recoveries in the range of 98.7–108.6%. The minimum sampling rate was about 100 samples/h. The possible mechanism of this inhibitory CL was studied by fluorescence spectrophotometer and UV–vis spectrophotometer. Copyright © 2009 John Wiley & Sons, Ltd.     

Utility of gold nanoparticles in luminescence determination of trovafloxacin: comparison of chemiluminescence and fluorescence detection

Two novel sensitive sequential injection chemiluminescence analysis and fluorescence methods for trovafloxacin mesylate detection have been developed. The methods were based on the enhancement effect of gold nanoparticles on luminol–ferricyanide–trovafloxacin and europium(III)–trovafloxacin complex systems. The optimum conditions for both detection methods were investigated. The chemiluminescence signal was emitted due to the enhanced effect of gold nanoparticles on the reaction of luminol–ferricyanide–trovafloxacin in an alkaline medium. The response was linear over a concentration range of 1.0 × 10^–9 to 1.0 × 10^–2 mol/L (%RSD = 1.3), (n = 9, r = 0.9991) with a detection limit of 1.7 × 10^–10 mol/L (S/N = 3). The weak fluorescence intensity signal of the oxidation complex of europium(III)–trovafloxacin was strongly enhanced by gold nanoparticles and detected at λ_ex = 330 and λ_em = 540 nm. Fluorescence detection enabled the determination of trovafloxacin mesylate over a linear range of 1.0 × 10^–8 to 1.0 × 10^–3 mol/L (%RSD = 1.2), (n = 6, r = 0.9993) with a detection limit of 3.3 × 10^–9 mol/L. The proposed methods were successfully applied to the determination of the studied drug in its bulk form and in pharmaceutical preparations. The results were treated statistically and compared with those obtained from other reported methods. Copyright © 2015 John Wiley & Sons, Ltd.