Fang Chen

Highly sensitive and selective determination of cupric ions by using N,N′-bis(salicylidene)-o-phenylenediamine as fluorescent chemosensor and related applications

A sensitive and selective copper(II) fluorescence Schiff base chemical sensor receptor 1 (short for N,N-bis(salicylidene)-o-phenylenediamine) has been prepared. The fluorescence of receptor 1 in pH 8.2 phosphate buffer solution can be dramatically quenched by Cu(2+), whereas it is nearly unaffected by other metal ions. Based on this, a sensitive and selective fluorescent quenching method for Cu(2+) detection has been established. Under the optimum conditions, a good linear relation exists between the quenching efficiency (F0/F) and the concentration of Cu(2+) in the range of 1.0 × 10(-7)-2.5 × 10(-6) mol L(-1). The detection limit (3σ) for Cu(2+) determination is 2.0 × 10(-8) mol L(-1). The present method has been successfully used for quantification of Cu(2+) in soybean milk powder. Furthermore, the fluorescence switch property of the system was explored, and the system might be applied for determination of glutathione and construction of molecular logic gate.

Determination of L-cysteine base on the reversion of fluorescence quenching of calcein by copper(II) ion

AbstractWe report on a simple and sensitive method for the determination of L-cysteine (Cys). It is based on a redox reaction between the non-fluorescent Cu(II)-calcein complex and Cys which results in fluorescence recovery of calcein. When Cys is added to a solution of the Cu(II)-calcein complex, Cu(II) is reduced to Cu(I), and calcein is released to form a strongly fluorescent complex with Zn(II). The effect was used to develop a fluorescence enhancement method for the determination of Cys. Under the optimum conditions, the increase in signal intensity is linear in the range from 3.0u2009×u200910−7 to 1.2u2009×u200910−5xa0molxa0L−1, with a correlation coefficient (R) of 0.9978. The limit of detection (3σ) is 4.0u2009×u200910−8xa0molxa0L−1. The relative standard deviation (RSD) in the determination of 11 samples containing 5.0u2009×u200910−6xa0molxa0L−1 of Cys was 3.5%. There is little interference by common ions and other amino acids. The method, which is simple, rapid, and sensitive, was successfully applied to the determination of Cys in human serum samples.n FigureCalcein is strongly fluorescent in water solution. It could form a non-fluorescent complex with Cu2+. When Cys is added to a solution of the Cu(II)-calcein complex, Cu(II) is reduced to Cu(I), and calcein is released to form a strongly fluorescent complex with Zn(II).

A Direct Chemiluminescence Method for the Determination of Prulifloxacin Using Tris-(4,7-Diphenyl-1,10-Phenanthrolinedisulfonic Acid) Ruthenium(II)–Cerium(IV) System

Abstract A simple, rapid, injection chemiluminescence method is described for the determination of prulifloxacin, a commonly used antibiotic. A strong chemiluminescence signal was detected when a mixture of the analyte and tris-(4,7-diphenyl-1,10-phenanthrolinedisulfonic acid)ruthenium(II) was injected into cerium(IV) sulfate. The chemiluminescence signal is proportional to the concentration of prulifloxacin in the range 4.0 × 10−8–9.0 × 10−6 mol L−1. The detection limit is 1.0 × 10−8 mol L−1, and the relative standard deviation is 2.2% (n = 11) for the determination of 8.0 × 10−7 mol L−1 prulifloxacin. The proposed method was successfully applied to the determination of prulifloxacin in pharmaceutical preparations in capsules, spiked serum, and urine samples.

Highly Sensitive Spectrofluorimetric Determination of Trace Amounts of Superoxide Dismutase Using a Prulifloxacin-Terbium(III) Probe

Abstract A new spectrofluorimetric method was developed for determining superoxide dismutase. The interactions between prulifloxacin (PUFX) –Tb3+ complex and superoxide dismutase had been studied by using UV-Vis absorption and fluorescence spectra. Using prulifloxacin–Tb3+ as a fluorescence probe, under optimum conditions, superoxide dismutase could remarkably enhance the fluorescence intensity of the prulifloxacin–Tb3+ complex at λ = 545 nm, and the enhanced fluorescence intensity was in proportion to the concentration of superoxide dismutase. Optimum conditions for the determination of superoxide dismutase were also investigated. The dynamic range for the determination of superoxide dismutase was 0.032 to 22.56 µg mL−1, and the detection limit (S/N = 3) was 1.5 ng 4 mL−1. This method was simple, practical, and relatively free of interference from coexisting substances and could be successfully used to determine superoxide dismutase in the plant and blood samples. The mechanism of fluorescence enhancement of prulifloxacin–Tb3+ complex by superoxide dismutase was also discussed.

Fluorescence Probe Enhanced Spectrofluorimetric Method for the Determination of Prulifloxacin in Pharmaceutical Formulations and Biological Fluids

Abstract Spectrofluorimetry for the determination of prulifloxacin (PUFX) was developed based on the strong fluorescence of PUFX after adding fluorescence probe yttrium in buffer solution (pH = 6.80), and various factors of influencing fluorescence have been researched. Under the optimum conditions, the liner range was 2.0 × 10−8 to 9.1 × 10−6 mol L−1 and the detection limit was 8.5 × 10−9 mol L−1. The relative standard deviation was 2.1% for 11 measurements of 5.0 × 10−7 mol L−1 PUFX standard solution. The mechanism of the sensitizing effect of probe was discussed. The method was applied for the determination of PUFX in actual sample; the result obtained was satisfactory.

Determination of ethylenediaminetetraacetic acid base on the reversion of fluorescence quenching of 2-pyridinecarbaldehyde-p-phenyldihydrazone by ferric iron.

A fast and sensitive fluorometric method for determination of an emerging pollutant, ethylenediaminetetraacetic acid (EDTA), was proposed based on the reversion of fluorescence quenching of 2-pyridinecarbaldehyde-p-phenyldihydrazone by ferric iron. It was found that Fe(3+) could selectively quench the fluorescence of 2PC-PPH, while EDTA could recover it due to its strong coordination ability with Fe(3+). Based on this, we established an Off and On fluorescence method for determination of EDTA. Under the optimum conditions, the linear range and detection limit (3S/N) for EDTA determination were 2.0 × 10(-6)~1.4 × 10(-5) mol L(-1) and 1.5 × 10(-7) mol L(-1), respectively. The relative standard deviation for the determination of 7.0 × 10(-6)mol L(-1) EDTA was 3.7% (n=11). The method was successfully applied to determination of EDTA in tap water, lake water and investigating degradation of EDTA by TiO2/UV process.

Determination of DNA based on fluorescence quenching of terbium doped carbon dots

AbstractThis work describes the preparation of carbon dots doped with terbium(III) (Tb-CDs) via a hydrothermal method, starting from terbium ion and ethylenediamine. The size, composition and spectral properties of the Tb-CDs were characterized by transmission electron microscopy, infrared spectra, and fluorescence spectra. The results show that doping of the CDs with Tb(III) reduces the particle size and results in more uniform particles, while fluorescence (at excitation/emission peaks of 380/475xa0nm) is strongly enhanced. The interaction between Tb-CDs and ct-DNA results in fluorescence quenching of Tb-CDs. The findings were exploited to design a quenchometric method for the determination of ct-DNA. The signal drops linearly in the 80xa0ng·mL−1 to 50xa0μg·mL−1 ct-DNA concentration range, and the detection limit is 53xa0ng·mL−1. The method was applied to the determination of ct-DNA in spiked samples and gave satisfactory results. The possible fluorescence quenching mechanism (which is mainly static)xa0was investigated using thexa0Stern–Volmer equation and thermodynamic equations.n Graphical abstractA kind of carbon dots doped with terbium(III) (Tb-CDs) were prepared via a hydrothermal method, using terbium ion and ethylenediamine as precursor. Doping with Tb(III) reduced the particle size of CDs and results in uniform particle size and stronger fluorescence. The interaction between the Tb-CDs and dsDNA results in quenching of the fluorescence of Tb-CDs and can be applied to determination of dsDNA.