Spectrofluorimetric determination of thiols by use of N[P-(2-benzoxazolyl)phenyl]maleimide

The weak fluorescence of N-[P-(2-benzoxazolyl)phenyl]maleimide (BOPM) can be greatly enhanced by thiol-containing compounds. A sensitive and simple spectrofluorimetric method based on the use of BOPM has been developed for the determination of thiols such as cysteine (Cys) and reduced glutathione (GSH). Calibration plots were linear in the concentration range from 0 to 1.6 x 10(-7) mol L(-1) for Cys and 0 to 1.7 x 10(-7) mol L(-1) for GSH. The detection limits (3a) were 2.36 x 10(-10) mol L(-1) for Cys and 1.49 x 10(-10) mol L(-1) for GSH. Many other amino acids (present at 100-fold greater concentrations) did not interfere with the determination. The proposed method has been used for the determination of Cys in protein hydrolysate and cystine electrolyte or GSH in serum, with recoveries of 95.4-103.7%.     

Spectrofluorimetric determination of thiols by use of N-[P-(2-benzoxazolyl)- phenyl]maleimide

The weak fluorescence of N-[P-2-benzoxazolyl)phenyl]maleimide (BOPM) can be greatly enhanced by thiol-containing compounds. A sensitive and simple spectrofluorimetric method based on the use of BOPM has been developed for the determination of thiols such as cysteine (Cys) and reduced glutathione (GSH). Calibration plots were linear in the concentration range from 0 to 1.6 × 10^–7 mol L^–1 for Cys and 0 to 1.7 × 10^–7 mol L^–1 for GSH. The detection limits (3σ) were 2.36 × 10^–10 mol L^–1 for Cys and 1.49 × 10^–10 mol L^–1 for GSH. Many other amino acids (present at 100-fold greater concentrations) did not interfere with the determination. The proposed method has been used for the determination of Cys in protein hydrolysate and cystine electrolyte or GSH in serum, with recoveries of 95.4–103.7%.     

Spectrofluorimetric determination of cysteine by 5-maleimidyl-2-(m-methylphenyl)benzoxazole

A new thiol weak-fluorescence probe, 5-maleimidyl-2-(m-methylphenyl)benzoxazole (MMPB), gives a highly fluorescence product in the presence of Cys. In this paper, MMPB has been developed for the fluorimetric determination of cysteine (Cys). At lambda(ex)/lambda(em) = 305.6/425.6 nm, the linear range is from 0 to 3.3 x 10(-7) mol l(-1) and the detection limit (sigma = 3) of 6.2 x 10(-10) mol l(-1). The main advantage of this method lies in the relative high selectivity compared with the methods using other N-substituted maleimide type of thiol reagents, in which 0.15-fold (molar ratio) of GSH is allowed and most of other amino acids at 100-fold (molar ratio) level had no obvious effect on the results. The proposed method has been applied to the determination of Cys in real samples.     

Direct spectrofluorimetric determination of glutathione in biological samples using 5-maleimidyl-2-(m-methylphenyl) benzoxazole

A new thiol fluorescence probe, 5-maleimidyl-2-(m-methylphenyl)benzoxazole (MMPB) has been developed for the direct determination of reduced glutathione (GSH) in real samples. Compared to the reported N-substituted maleimide type of thiol reagents, the main advantage of MMPB is its rather high selectivity for GSH to cysteine (Cys), which often coexists with GSH in biological samples. Under mild conditions similar to the physiological environment, MMPB reacted with GSH to give a highly fluorescent derivative with the excitation and emission wavelengths of 299.2 and 355.8 nm, respectively. In the presence of 0.40-fold (molar ratio) of Cys, a linear relationship was found in the range of 0-1.62×10⁻⁷ mol l⁻¹ with the detection limit (3σ) of 3.23×10⁻¹⁰ mol l⁻¹ for GSH determination. Many other amino acids (100-fold) did not interfere with the determination. Since the molar ratio of Cys to GSH in mammalian tissues and blood does not exceed the value of 0.40:1, the proposed method has been used in the direct determination of GSH in these kinds of biological samples, such as human blood, pig’s liver and heart with the recoveries of 94.3-104.5%     

Sensitive detection of biothiols and histidine based on the recovered fluorescence of the carbon quantum dots–Hg(II) system

In this paper, we presented a novel, rapid and highly sensitive sensor for glutathione (GSH), cysteine (Cys) and histidine (His) based on the recovered fluorescence of the carbon quantum dots (CQDs)–Hg(II) system. The CQDs were synthesized by microwave-assisted approach in one pot according to our previous report. The fluorescence of CQDs could be quenched in the presence of Hg(II) due to the coordination occurring between Hg(II) and functional groups on the surface of CQDs. Subsequently, the fluorescence of the CQDs–Hg(II) system was recovered gradually with the addition of GSH, Cys or His due to their stronger affinity with Hg(II). A good linear relationship was obtained from 0.10 to 20 μmol L⁻¹ for GSH, from 0.20 to 45 μmol L⁻¹ for Cys and from 0.50 to 60 μmol L⁻¹ for His, respectively. This method has been successfully applied to the trace detection of GSH, Cys or His in human serum samples with satisfactory results. The proposed method was simple in design and fast in operation, which demonstrated great potential in bio-sensing fields.     

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

We 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 3.0?×?10^?7 to 1.2?×?10^?5?mol?L^?1, with a correlation coefficient (R) of 0.9978. The limit of detection (3σ) is 4.0?×?10^?8?mol?L^?1. The relative standard deviation (RSD) in the determination of 11 samples containing 5.0?×?10^?6?mol?L^?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.

Simultaneous femtomole determination of cysteine, reduced and oxidized glutathione, and phytochelatin in maize (Zea mays L.) kernels using high-performance liquid chromatography with electrochemical detection

Thiol compounds such as cysteine (Cys), reduced (GSH) and oxidized (GSSG) gluathione, and phytochelatins (PCs) play an important role in heavy metal detoxification in plants. These thiols are biological active compounds whose function is elimination of oxidative stress in plant cells. The aim of our work was to optimise sensitive and rapid method of high-performance liquid chromatography coupled with electrochemical detector (HPLC-ED) for determination of the abovementioned thiol compounds in maize (Zea mays L.) kernels. New approach for evaluation of HPLC-ED parameters is described. The most suitable isocratic mobile phase for the separation and detection of Cys, GSH, GSSG and PC2 consisted of methanol (MeOH) and trifluoroacetic acid (TFA). In addition, the influence of concentrations of TFA and ratio of MeOH:TFA on chromatographic separation and detection of the thiol compounds were studied. The mobile phase consisting from methanol and 0.05% (v/v) TFA in ratio 97:3 (%; v/v) was found the most suitable for the thiol compounds determination. Optimal flow rate of the mobile phase was 0.18 ml min(-1) and the column and detector temperature 35 degrees C. Hydrodynamic voltammograms of all studied compounds was obtained due to the selection of the most effective working electrodes potentials. Two most effective detection potentials were selected: 780 mV for the GSSG and PC2 and 680 mV for determination of Cys and GSH. The optimised HPLC-ED method was capable to determine femtomole levels of studied compounds. The detection limits (3 S/N) of the studied thiol compounds were for cysteine 112.8 fmol, GSH 63.5 fmol, GSSG 112.2 fmol and PC2 2.53 pmol per injection (5 microl). The optimised HPLC-ED method was applied to study of the influence of different cadmium concentrations (0, 10 and 100 microM Cd) on content of Cys, GSH, GSSG and PC2 in maize kernels. According to the increasing time of Cd treatment, content of GSH, GSSG and PC2 in maize kernels increased but content of Cys decreased. Decreasing Cys concentration probably relates with the increasing GSH and phytochelatins synthesis.     

Preparation of a novel fluorescence nanoparticles and its application in the determination of Hg(II)

The strong fluorescence 2-vinylnaphthalene and acrylic acid polymer nanoparticles have been prepared under ultrasonic radiation. Based on the fluorescence quenching of polymer by Hg(II), a method for the selective determination of Hg(II) was developed. The reaction conditions between Hg(II) and polymer were investigated in detail. The assay is very few interference stable fluorescence signals (at least 2h), simple instrument (common spectrofluorometer) and simple step. Under optimal experimental conditions, a limit of detection of 0.01 microg ml(-1) was achieved. The calibration curve was linear over the concentration range 0.04-0.1 microg ml(-1) with a correlation coefficient of 0.9927. The proposed method has been applied to the selective quantification of Hg(II) in synthetic samples with the satisfactory results.     

Amperometric determination of glutathione and cysteine on a Pd-IrO(2) modified electrode with high performance liquid chromatography in rat brain microdialysate

A Pd/IrO(2) co-electrodeposited glassy carbon electrode was prepared and the electrochemical behavior of glutathione (GSH) at this chemically modified electrode (CME) has been studied by cyclic voltammetry (CV). The results indicated that the modified electrode efficiently exhibited electrocatalytic oxidation for GSH with relatively high sensitivity, stability, and long-life. Coupled with high-performance liquid chromatography (HPLC), the Pd/IrO(2) modified electrode was utilized for the electrochemical detection (ECD) of the thiocompounds, glutathione and cysteine (Cys). The peak currents were linear with the substance concentrations in the range of 1.0 x 10(-5) mol L(-1) to 8.0 x 10(-4) mol L(-1) for GSH and 4.0 x 10(-6) mol L(-1) to 2.0 x 10(-4) mol L(-1) for Cys. The detection limits were 2.0 x 10(-6) mol L(-1) for GSH and 5.0 x 10(-7) mol L(-1) for Cys with S/N of 3. The method has been successfully applied to assess the contents of GSH and Cys in rat brain microdialysates.     

A regenerable fluorescent quantum dot based nanoprobe for zinc(II), and the design of a molecular logic gate

We report on a simple, sensitive and regenerable fluorescent nanoprobe for Zn(II) ion. It is based on the use of glutathione capped CdTe quantum dots (GSH-CdTe Q-dots). The bright fluorescence of these Q-dots is quenched on addition of diethylenetriaminepentaacetic acid (DTPA) due to the binding of DTPA to GSH. If, however, Zn(II) is added, it will bind DTPA and detach it from the surface of the Q-dots, this resulting in the fluorescence recovery. Under optimum conditions, the intensity of the restored fluorescence is proportional to the concentration of Zn(II) in the 0.48 to 90 μmol · L⁻¹ range, with a limit of detection of 0.14 μmol · L⁻¹. The nanoprobe was applied to the determination of Zn(II) in spiked tap water and river water and gave satisfactory results. The findings were also applied to design a molecular logic gate where DTPA acts as the first input to the system by quenching the fluorescence of the GSH-CdTe Q-dots. Zn(II) acts as the second input and causes the detachment of DTPA from the Q-dots and a restoration of fluorescence. This system therefore represents a new IMP (IMPLICATION) logic gate.

We describe a fluorescent nanoprobe for Zn(II) based on quantum dots, and its use in an IMP molecular logic gate. The nanoprobe was successfully applied to the determination of Zn(II) in spiked tap water and river water.

     

Spectrofluorimetric determination of zinc in foods with 8-(p-toluenesulphonamido)quinoline in micellar medium

A new method for the spectrofluorimetric determination of zinc with 8-(p-toluene- sulphonamido)quinoline in a Brij-35 micellar medium has been developed. This method allows the determination of 8-550 ng/ml Zn(II) and is relatively free from interferences. It has been applied to food samples with satisfactory results.     

Enhancement of the fluorescence of the beryllium-morin complex by non-ionic surfactants

The effect of surfactants on the fluorescence of the beryllium-morin system has been studied. Non-ionic surfactants strongly enhance the fluorescence intensity of the beryllium complex. The addition of Triton X-100 makes possible the fluorimetric determination of submicrogram quantities of beryllium in feebly acidic media (pH 5.8-6.2, hexamine buffer). The fluorescence is excited at 440 nm and measured at 530 nm. The calibration graph is linear up to 10 ng/ml Be and the detection limit is 0.04 ng/ml. The relative standard deviation is 2.2% for beryllium at 0.5 ng/ml concentration and 0.7% for 5.0 ng/ml. The effects of 25 ions commonly found in water have also been studied; Zn(2+) and F(-) give the main interference. The method has been applied to the determination of beryllium in water pollution quality-control samples with satisfactory results.     

Simultaneous determination of copper, mercury and zinc in water with a tailored fluorescent bipyridine ligand entrapped in silica sol-gel

A novel fluorescent ligand, (4-[(E)-2-(4'-methyl-2,2'-bipyridin-4-yl)vinyl]phenol) (abbreviated BSOH), has been designed and prepared for simultaneous determination of heavy metals in water. Its photophysical and photochemical properties in the absence and in the presence of Cd(II), Cu(II), Hg(II), Ni(II) and Zn(II) were determined, and the respective complexation constants (7.4 × 10(3)-2.8 × 10(8) l mol(-1)) and stoichiometries were extracted thereof. The Stern-Volmer emission intensity and lifetime plots indicate an efficient static quenching of the indicator dye with the heavy metals. The BSOH fluorescent reagent has been successfully immobilised in a silica sol-gel matrix for automation of the analytical method, and the sensing phase demonstrated a reversible response to Cu(II), Hg(II) and Zn(II) but not to Cd(II) and Ni(II). Characterisation of the sensor showed that its response to those heavy metals is linear in the 2.5 to 50 μmol l(-1) range, with a response time (t (90)) on the order of 100 min, providing detection limits of 9.0 × 10(-7), 4.7 × 10(-7) and 2.9 × 10(-7) mol l (-1) for Zn(II), Cu(II) and Hg(II), respectively. Due to the stability of the immobilised ligand, which presented no leaching from the sol-gel matrix, the simultaneous determination of the three cations in water was feasible by employing multivariate calibration techniques coupled to fluorescence quenching measurements. The sensor was validated with recovery tests by addition of Cu(II) and Hg(II) ions to spring waters, providing results with standard errors lower than 4.1 μmol l (-1).     

Efficient generation of volatile species for cadmium analysis in seafood and rice samples by a modified chemical vapor generation system coupled with atomic fluorescence spectrometry

A vapor generation procedure to determine Cd by atomic fluorescence spectrometry (AFS) has been established. Volatile species of Cd are generated by following reaction of acidified sample containing Fe(II) and l-cysteine (Cys) with sodium tetrahydroborate (NaBH₄). The presence of 5 mg L⁻¹ Fe(II) and 0.05% m/v Cys improves the efficiency of Cd vapor generation substantially about four-fold compared with conventional thiourea and Co(II) system. Three experiments with different mixing sequences and reaction times are designed to study the reaction mechanism. The results document that the stability of Cd(II)–Cys complexes is better than Cys–THB complexes (THB means NaBH₄) while the Cys–THB complexes have more contribution to improve the Cd vapor generation efficiency than Cd(II)–Cys complexes. Meanwhile, the adding of Fe(II) can catalyze the Cd vapor generation. Under the optimized conditions, the detection limit of Cd is 0.012 μg L⁻¹; relative standard deviations vary between 0.8% and 5.5% for replicate measurements of the standard solution. In the presence of 0.01% DDTC, Cu(II), Pb(II) and Zn(II) have no significant influence up to 5 mg L⁻¹, 10 mg L⁻¹and 10 mg L⁻¹, respectively. The accuracy of the method is verified through analysis of the certificated reference materials and the proposed method has been applied in the determination of Cd in seafood and rice samples.     

A multisite-binding fluorescent probe for simultaneous monitoring of mitochondrial homocysteine,cysteine and glutathione in live cells and zebrafish

Homocysteine(Hcy), cysteine(Cys) and glutathione(GSH) play crucial roles in redox homeostasis during mitochondria functions. Simultaneous differentiation and visualization of mitochondrial biothiols dynamics are significant for understanding cell metabolism and their related diseases. Herein, a multisitebinding fluorescent probe(MCP) was developed for simultaneous sensing of mitochondrial Cys, GSH and Hcy from three fluorescence channels for the first time. This novel probe exhibited rapid fluor...     

A highly sensitive assay for spectrofluorimetric determination of reduced glutathione using organic nano-probes

In this study, the new nanometer-sized fluorescent particles (1-pyrenemethylamine nanoparticles) have been prepared by reprecipitation method under ultrasonic radiation. These nanoparticles have the potential to overcome problems encountered by organic small molecules by combining the advantages of high photobleaching threshold, high quantum yield, long fluorescence lifetime, good chemical stability, and wide excitation spectral properties. These nanoparticles will be able to be directly used as fluorescent nanoparticles probe without modification. A new fluorimetric method for the determination of reduced glutathione (GSH) has been developed with these nanoparticles. Under optimal conditions, the organic nanoparticles reacted with GSH and o-phthalaldehyde (OPA) to give a highly fluorescent derivative in Na2CO3-HCl buffer (pH=9.0). The fluorescence excitation and emission wavelengths of fluorescent derivative were located at 345 and 400 nm, respectively. The relative fluorescence intensity (RF) was linear in the range of the GSH concentration from 8.0x10(-7) to 1.1x10(-4)moll(-1). Limit of detection of 7.1x10(-8)moll(-1) was achieved for the reduced glutathione. The method was validated and applied to the analysis of three synthetic samples containing reduced glutathione.     

Synthesis, characterization and applications of pyrocatechol modified amberlite XAD-2 resin for preconcentration and determination of metal ions in water samples by flame atomic absorption spectrometry (FAAS)

A new chelating resin is prepared by coupling Amberlite XAD-2 with pyrocatechol through an azo spacer, characterized (by elemental analysis, IR and TGA) and studied for preconcentrating Cd(II), Co(II), Cu(II), Fe(III), Ni(II) and Zn(II) using flame atomic absorption spectrometry (FAAS) for metal monitoring. The sorption is quantitative in the pH range 3.0-6.5, whereas quantitative desorption occurs instantaneously with 2 M HCl or HNO(3) The sorption capacity has been found to be in the range 0.023-0.092 mmol g(-1) of resin. The loading half time (t(1/2)) is 1.4, 4.8, 1.6, 3.2, 2.3 and 1.8 min, respectively for Cd, Co, Cu, Fe, Ni and Zn. The tolerance limits of electrolytes NaCl, NaBr, NaNO(3), Na(2)SO(4) and Na(3)PO(4) in the sorption of all the six metal ions (0.2 mug ml(-1)) are reported. The Mg(II) and Ca(II) are tolerable with each of them (0.2 mug ml(-1)) up to a concentration level of 0.01-1.0 M. The enrichment factor has been found to be 200 except for Fe and Cu for which the values are 80 and 100, respectively. The lowest concentration of metal ion for quantitative recovery is 5, 10, 20, 25, 10 and 10 mug l(-1) for Cd, Co, Cu, Fe, Ni and Zn, respectively. The simultaneous determination of all these metal ions is possible and the method has been applied to determine all the six metal ions in tap and river water samples (RSD相似文献   

1,8-Dihydroxyanthraquinone anchored on silica gel: synthesis and application as solid phase extractant for lead(II), zinc(II) and cadmium(II) prior to their determination by flame atomic absorption spectrometry

A new chelating matrix has been prepared by immobilizing 1,8-dihydroxyanthraquinone (DHAQ) on silica gel modified with (3-aminopropyl)triethoxysilane. After characterizing the matrix with thermogravimetric analysis (TGA), cross polarization magic angle spinning (CPMAS) NMR and diffuse reflectance infrared fourier transformation (DRIFT) spectroscopy, it has been used to preconcentrate Pb(II), Cd(II) and Zn(II) prior to their determination by flame atomic absorption spectrometry. The optimum pH ranges for quantitative sorption are 6.0-7.5, 7.0-8.0 and 6.0-8.0 for Pb, Zn, and Cd, respectively. All the metal ions can be desorbed with 2 mol l(-1) HCl/HNO(3). The sorption capacity of the matrix has been found to be 76.0, 180.0 and 70.2 mumol g(-1) for Pb, Zn and Cd, respectively, with the preconcentration factor of approximately 200. The limits upto which electrolytes NaNO(3), NaCl, NaBr, Na(2)SO(4), Na(3)PO(4) sodium citrate, EDTA, glycine and humic acid and cations Ca(II), Mg(II), Cu(II), Co(II), Ni(II), Mn(II) Al(III), Cr(III) and Fe(III) can co-exist with the metal ions during their sorption without any adverse effect are reported. The lowest concentration of metal ions for quantitative recovery is 5.0 ng ml(-1) The simultaneous enrichment and determination of all the metals is possible if total load of metal ions is less than sorption capacity. The flame AAS was used to determine these metal ions in underground, tap and river water samples (relative standard deviation (R.S.D.)相似文献   

柱前衍生高效液相色谱-荧光检测法测定水稻中7种巯基化合物

建立了水稻中半胱氨酸(Cys)、谷胱甘肽(GSH)和植物螯合肽(phytochelatin, PC:PC₂、PC₃、PC₄、PC₅、PC₆)7种巯基化合物的柱前衍生高效液相色谱-荧光检测分析方法.样品经0.1%三氟乙酸(TFA)(含6.3 mmol/L二乙烯三胺五乙酸(DTPA))超声提取,然后以单溴二胺(mBrB)为衍生剂在pH 8.0的4-羟乙基哌嗪丙磺酸(HEPPS)缓冲溶液中衍生化.采用的色谱分离柱为Agilent Eclipse plus C_l8柱,流动相为0.1%TFA(pH 2.5)和100%乙腈(ACN),梯度洗脱,流速为0.8 mL/min.荧光检测的激发波长和发射波长分别为380 nm和470 nm.结果表明,7种巯基化合物在0.7~100.0 mg/L范围内,峰面积与质量浓度之间的线性关系良好(r²≥0.9991);检出限为0.03~0.20 mg/L;加标回收率为89.26%~99.42%,相对标准偏差为2.05%~5.87%.该方法准确、灵敏度高、重现性好,为水稻中巯基化合物的研究提供了检测手段.