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1.
A highly sensitive and simple spectrofluorimetric method for the determination of dobutamine hydrochloride based on its inhibitory effect on the hemoglobin‐catalyzed reaction of H2O2 and l ‐tyrosine was developed. The relationship between the concentration of dobutamine hydrochloride and the fluorescence quenching (ΔF) of the system is linear under the optimal experimental conditions. The calibration graph is linear in the range 2.00 × 10‐7 to 3.00 × 10‐6 g/mL with a limit of detection of 4.83 × 10‐9 g/mL. This method can be used for the determination of dobutamine hydrochloride in its pharmaceutical formulations and in urine with satisfactory results. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

2.
In weak acidic medium, the anticancer antibiotics bleomycin A5 (BLMA5) and bleomycin A2 (BLMA2) bind with halofluorescein dyes, such as erythrosin (Ery), eosin Y (EY) and eosin B (EB), to form ion‐association complexes, which causes fluorescence quenching of halofluorescein dyes. The quenching values (ΔF) are directly in proportional to the concentrations of bleomycins over the range 0.09–2.5 µg/mL. Based on this, a fluorescence quenching method for the determination of BLMA5 and BLMA2 has been developed. The dynamic range is 0.12–2.5 µg/mL for the determination of BLMA5 and 0.09–2.0 µg/mL for BLMA2, with detection limits (3σ) of 0.04 µg/mL for BLMA5, 0.03 µg/mL for BLMA2, respectively. It has been applied to determine the two antibiotics in human serum, urine and rabbit serum samples. The recovery is in the range 90–102%. In this work, the optimum reaction conditions and the spectral characteristics of the fluorescence are investigated. The reasons for fluorescence quenching are discussed, based on the fluorescence theory. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

3.
In Britton‐Robinson (BR) buffer medium (pH 3.3), carbazochrome sodium sulfonate (CSS) can react with some aromatic amino acids such as tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe) to form a 1:1 complex by electrostatic attraction, aromatic stacking interaction and Van der Waals' force, resulting in fluorescence quenching of these amino acids. Maximum quenching wavelengths were located at 352 nm (CSS‐Trp system), 303 nm (CSS‐Tyr system) and 284 nm (CSS‐Phe system), respectively. The fluorescence quenching value (ΔF) was proportional to the concentration of CSS in a certain range. The fluorescence quenching method for the determination of CSS showed high sensitivity, with detection limits of 31.3 ng/mL (CSS‐Trp system), 44.6 ng/mL (CSS‐Tyr system) and 315.0 ng/mL (CSS‐Phe system), respectively. The optimum conditions of the reaction conditions and the effect of coexisting substances were investigated and results showed that the method had good selectivity. The method was successfully applied for the rapid determination of CSS in blood and urine samples. Based on the bimolecular quenching constant Kq, the effect of temperature and Stern‐Volmer plots, this study showed that quenching of fluorescence of amino acids by CSS was a static quenching process. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

4.
CdTe quantum dots (QDs) capped with different stabilizers, i.e. thioglycolic acid (TGA), 3‐mercaptopropionic acid (MPA) and glutathione (GSH) were investigated as fluorescent probes for the determination of Cu2+. The stabilizer was shown to play an important role in both the sensitivity and selectivity for the determination of Cu2+. TGA‐capped CdTe QDs showed the highest sensitivity, followed by the MPA and GSH‐capped CdTe QDs, respectively. The TGA‐ and MPA‐capped CdTe QDs were not selective for Cu2+ that was affected by Ag+. The GSH‐capped CdTe QDs were insensitive to Ag+ and were used to determine Cu2+ in water samples. Under optimal conditions, quenching of the fluorescence intensity (F0/F) increased linearly with the concentration of Cu2+ over a range of 0.10–4.0 µg/mL and the detection limit was 0.06 µg/mL. The developed method was successfully applied to the determination of Cu2+ in water samples. Good recoveries of 93–104%, with a relative standard deviation of < 6% demonstrated that the developed simple method was accurate and reliable. The quenching mechanisms were also described. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

5.
In pH 4.99‐6.06 Britton‐Robinson (BR) buffer medium, 6‐benzylaminopurine (6‐BA) reacted with Na2WO4 to form 1:1 anionic chelate (6‐BA·WO4)2‐, which further reacted with rhodamine 6G to form ternary ion complexes at room temperature. This resulted in a significant enhancement of resonance Rayleigh scattering (RRS) with a maximum RRS wavelength of 316 nm. Meanwhile, the fluorescence of the solution was quenched and excitation (λex) and emission (λem) wavelengths of the fluorescence were 290 and 559 nm, respectively. Intensities of RRS enhancing (ΔIRRS) and fluorescence quenching (ΔIF) were directly proportional to concentrations of 6‐BA. As a result, RRS and fluorescence quenching for determination of trace amounts of 6‐BA were developed. Under optimal conditions, linear ranges and detection limits of the two methods were 0.05‐15.00 µg/mL and 8.2 ng/mL (RRS), 0.50‐15.00 µg/mL and 17.0 ng/mL, respectively. It was found that the RRS method was superior to fluorescence quenching. The influence of these methods were investigated and results showed that RRS had good selectivity. RRS was applied to determine 6‐BA in vegetable samples with satisfactory results. Furthermore, the reaction mechanisms of the ternary ion‐association system are discussed. In addition, the polarization experiment revealed that the resonance light scattering (RLS) peak of Na2WO4‐6‐BA‐R6G consisted mainly of depolarized resonance fluorescence and resonance scattering. It was speculated that light emission fluorescence energy (EL) transformed into resonance light scattering energy (ERLS), which was a key reason for enhancement of RRS. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

6.
A rapid, novel and cost-effective spectrofluorimetric method developed to determine moxifloxacin (MFX) in pharmaceutical preparations because MFX in a pH 10 medium could reduce the fluorescence intensity of l -tryptophan. The maximum fluorescence excitation and emission wavelengths were found to be 280 and 363 nm respectively. A range of factors affecting fluorescence quenching and the effect of co-existing substances were investigated. Fluorescence quenching values (ΔF = FL-tryptophanFMoxi-L-tryptophan) displayed a strong linear relationship with the MFX concentration ranging from 0.2 to 8.0 μg/ml under optimum conditions. The limit of detection was found to be 6.1 × 10−4 μg/ml. The proposed method was shown to be suitable for MFX determination in pharmaceutical tablets and biological fluids by the linearity, recovery and limit of detection. The spectrofluorimetric approach that has been developed is extremely eco-friendly, as evidenced by the fact that all the experimental components and solvents were safe for the environment.  相似文献   

7.
A highly sensitive, simple and rapid spectrofluorimetric method was developed for the determination of azelastine HCl (AZL) in either its pure state or pharmaceutical dosage form. The proposed method was based on measuring the native fluorescence of the studied drug in 0.2 M H2SO4 at λem = 364 nm after excitation at λex = 275 nm. Different experimental parameters were studied and optimized carefully to obtain the highest fluorescence intensity. The proposed method showed a linear dependence of the fluorescence intensity on drug concentration over a concentration range of 10–250 ng/mL, with a limit of detection of 1.52 ng/mL and limit of quantitation of 4.61 ng/mL. Moreover, the method was successfully applied to pharmaceutical preparations, with percent recovery values (± SD) of 99.96 (± 0.4) and 100.1 (± 0.52) for nasal spray and eye drops, respectively. The results were in good agreement with those obtained by the comparison method, as revealed by Student's t‐test and the variance ratio F‐test. The method was extended to study the stability of AZL under stress conditions, where the drug was exposed to neutral, acidic, alkaline, oxidative and photolytic degradation according to International Conference on Harmonization (ICH) guidelines. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

8.
The aim of this work is to optimize a spectrofluorimetric method for the determination of cefdinir (CFN) using the Taguchi method. The proposed method is based on the oxidative coupling reaction of CFN and cerium(IV) sulfate. The quenching effect of CFN on the fluorescence of the produced cerous ions is measured at an emission wavelength (λem) of 358 nm after excitation (λex) at 301 nm. The Taguchi orthogonal array L9 (34) was designed to determine the optimum reaction conditions. The results were analyzed using the signal‐to‐noise (S/N) ratio and analysis of variance (ANOVA). The optimal experimental conditions obtained from this study were 1 mL of 0.2% MBTH, 0.4 mL of 0.25% Ce(IV), a reaction time of 10 min and methanol as the diluting solvent. The calibration plot displayed a good linear relationship over a range of 0.5–10.0 µg/mL. The proposed method was successfully applied to the determination of CFN in bulk powder and pharmaceutical dosage forms. The results are in good agreement with those obtained using the comparison method. Finally, the Taguchi method provided a systematic and efficient methodology for this optimization, with considerably less effort than would be required for other optimizations techniques. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

9.
A new fluorescent probe, 4‐N,N‐di(2‐hydroxyethyl)imino‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (HINBD) was synthesized in a single step with reasonably good yield. The water‐soluble HINBD emits strongly in the visible region (λex = 479 nm, λem = 545 nm) and is stable over a wide range of pH values. It was found that vitamin B12 (VB12) had the ability to quench the fluorescence of HINBD, and the quenched fluorescence intensity was proportional to the concentration of VB12. A method for VB12 determination based on the quenching fluorescence of HINBD was thus established. Interference effects of various substances, including sugars, vitamins, amino acids, inorganic cations and some organic substances have been studied. Under optimal conditions, the linear range is 0.0–2.4 × 10–5 mol/L. The determination limit is 8.3 × 10–8 mol/L. The method was applied to measure VB12 in pharmaceutical preparations with satisfactory results. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

10.
The quenching of variable fluorescence yield (qN) and the quenching of dark level fluorescence yield (q0) directly atributable to high-energy-state fluorescence quenching (qE) was studied to distinguish between energy dissipation in the antenna and light harvesting complexes (antenna quenching) and energy dissipation at the reaction centres (reaction centre quenching). A consistent relationship was obtained between qN and q0 in barley leaves, the green alga Dunaliella C9AA and in pea thylakoids with 2,3,5,6-tetramethyl-p-phenylene diamine (DAD) as mediator of cyclic electron flow around PS 1. This correlated well with the relationship obtained using m-dinitrobenzene (DNB), a chemical model for antenna quenching, to quench fluorescence in Dunaliella C9AA or pea thylakoids. The results also correlated reasonably well with theoretical predictions by the Butler model for antenna quenching, but did not correlate with the predictions for reaction centre quenching. It is postulated that qE quenching therefore occures in the antenna and light harvesting complexes, and that the small deviation from the Butler prediction is due to PS 2 heterogeneity.Abbreviations 9-aa 9-aminoacridine - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - EDTA Ethylenediaminetetra-acetic acid - Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid - Mes 2-(N-morpholino) prophanesulfonate - PS 1 photosystem 1 - PS 2 photosystem 2 - QA and QB primary and secondary stable electron acceptors of photosystem 2 - qN non-photochemical fluorescence quenching coefficient - qE high-energy-state fluorescence quenching coefficient - q0 quenching coefficient for F0 - F0 dark level fluorescence yield - Fm maximum fluorescence yield - Fv variable fluorescence yield - Fv/Fm ratio of variable to total fluorescence yield - DAD 2,3,5,6-tetramethyl-p-phenylene diamine - DNB m-dinitrobenzene  相似文献   

11.
[目的]通过对蜜环菌(Armillaria mellea)的富硒驯化,研究各菌株硒耐受性、有机硒含量及生物活性的变化规律,从而获得生物活性更强的蜜环菌,并对富硒蜜环菌的生物学特征进行初步研究.[方法]以Na2SeO3为无机硒试剂对蜜环菌进行富硒驯化;采用氢化物原子荧光光谱法测定蜜环菌的硒含量,热水浴法测定蜜环菌的无机硒...  相似文献   

12.
A simple and sensitive flow injection–chemiluminescence (FI–CL) method has been developed for the determination of puerarin, based on the fact that puerarin can greatly inhibit CL of the luminol–H2O2–haemoglobin system. The inhibition of CL intensity was linear to the logarithm of the concentration of puerarin in the range 0.08–10.0 μg/mL (r2 = 0.9912). The limit of detection was 0.05 μg/mL (3σ) and the relative standard deviation (RSD) for 1.0 μg/mL (n = 11) of puerarin solution was 1.4%. Coupled with solid‐phase extraction (SPE) as the sample pretreatment, the determination of puerarin in biological samples and a preliminary pharmocokinetic study of puerarin in rats were performed. The recoveries for plasma and urine at three different concentrations were 89.2–110.0% and 91.4–104.8%, respectively. The pharmacokinetics of puerarin in plasma of rat coincides with the two‐compartment open model. The T1/2α, T1/2β, CL/F, VZ/F, AUC(0 – t), MRT(0 – ∞), Tmax and Cmax were 0.77 ± 0.21 h, 7.55 ± 2.64 h, 2.43 ± 1.02 L/kg/h, 11.40 ± 3.45 L/kg, 56.67 ± 10.65 mg/h/L, 5.04 ± 2.78 h, 1.00 ± 0.35 h and 19.70 ± 4.67 μg/mL, respectively. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

13.
A simple, highly sensitive and validated spectrofluorimetric method was applied in the determination of clonazepam (CLZ). The method is based on reduction of the nitro group of clonazepam with zinc/CaCl2, and the product is then reacted with 2‐cyanoacetamide (2‐CNA) in the presence of ammonia (25%) yielding a highly fluorescent product. The produced fluorophore exhibits strong fluorescence intensity at ?em = 383 nm after excitation at ?ex = 333 nm. The method was rectilinear over a concentration range of 0.1–0.5 ng/mL with a limit of detection (LOD) of 0.0057 ng/mL and a limit of quantification (LOQ) of 0.017 ng/mL. The method was fully validated and successfully applied to the determination of CLZ in its tablets with a mean percentage recovery of 100.10 ± 0.75%. Method validation according to ICH Guidelines was evaluated. Statistical analysis of the results obtained using the proposed method was successfully compared with those obtained using a reference method, and there was no significance difference between the two methods in terms of accuracy and precision. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

14.
Amino‐modified silica nanoparticles (FSNPs) doped with fluorescein isothiocyanate (FITC) were synthesized by using an aqueous core of reverse‐micelle microemulsion as the nanoreactor in an easy one‐pot method. Due to the FITC conjugating with (3‐aminopropyl)triethoxysilane (APTS), the nanoparticles prevent the FITC from leaching from the silica matrix when immersed in aqueous solution. SEM, FTIR, fluorescence lifetime, a photobleaching experiment and synchronous fluorescence spectra were used to characterize the FSNPs. The synchronous fluorescence signal of FSNPs was enhanced when trace amounts of γ‐globulin (γ‐G) were added. Under the optimal experimental conditions, the enhanced fluorescence intensity (ΔF) was linear with the concentration of γ‐G (c) in the range 0.3–4.8 µg/mL, with a detection limit of 0.04 µg/mL. The proposed method is simple, sensitive for the determination of trace amounts of γ‐G and used to determine the content of γ‐G in synthetic samples with satisfactory results. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

15.
A valid, sensitive and rapid spectrofluorimetric method has been developed and validated for determination of both tadalafil (TAD) and vardenafil (VAR) either in their pure form, in their tablet dosage forms or spiked in human plasma. This method is based on measurement of the native fluorescence of both drugs in acetonitrile at λem 330 and 470 nm after excitation at 280 and 275 nm for tadalafil and vardenafil, respectively. Linear relationships were obtained over the concentration range 4–40 and 10–250 ng/mL with a minimum detection of 1 and 3 ng/mL for tadalafil and vardenafil, respectively. Various experimental parameters affecting the fluorescence intensity were carefully studied and optimized. The developed method was applied successfully for the determination of tadalafil and vardenafil in bulk drugs and tablet dosage forms. Moreover, the high sensitivity of the proposed method permitted their determination in spiked human plasma. The developed method was validated in terms of specificity, linearity, lower limit of quantification (LOQ), lower limit of detection (LOD), precision and accuracy. The mean recoveries of the analytes in pharmaceutical preparations were in agreement with those obtained from the comparison methods, as revealed by statistical analysis of the obtained results using Student's t‐test and the variance ratio F‐test. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

16.
A sensitive spectrofluorimetric method was developed for the determination of tizanidine in human plasma, urine and pharmaceutical preparations. The method is based on reaction of tizanidine with 1‐dimethylaminonaphthalene‐5‐sulphonyl chloride (dansyl chloride) in an alkaline medium to form a highly fluorescent derivative that was measured at 511 nm after excitation at 383 nm. The different experimental parameters affecting the fluorescence intensity of tizanidine was carefully studied and optimized. The fluorescence–concentration plots were rectilinear over the ranges 50–500 and 20–300 ng/mL for plasma and urine, respectively, detection limits of 1.81 and 0.54 ng/mL and quantification limits of 5.43 and 1.62 ng/mL for plasma and urine, respectively. The method presents good performance in terms of linearity, detection and quantification limits, precision, accuracy and specificity. The proposed method was successfully applied for the determination of tizanidine in pharmaceutical preparations. The results obtained were compared with a reference method, using t‐ and F‐tests. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

17.
A sensitive and accurate spectrofluorimetric method has been developed for the determination of sulpiride in pharmaceutical preparations and human plasma. The developed method is based on the derivatization reaction of 2‐cyanoacetamide with sulpiride in 30% ammonical solution. The fluorescent derivatized reaction product exhibited maximum fluorescence intensity at 379 nm after excitation at 330 nm. The optimum conditions for derivatization reactions were studied and the fluorescence intensity versus concentration plot was found to be linear over the concentration range 0.2–20.0 µg/mL with a correlation coefficient of 0.9985. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.82 and 2.73 ng/mL, respectively. The proposed method was validated according to ICH guidelines. The effects of common excipients and co‐administered drugs were also studied. The accuracy of the method was checked using the standard addition method and percent recoveries were found to be in the range of 99.00–101.25% for pharmaceutical preparations and 97.00–97.80% for spiked human plasma. The method was successfully applied to commercial formulations and the results obtained for the proposed method were compared with a high‐performance liquid chromatography reference method and statistically evaluated using the Student's t‐test for accuracy and the variance ratio F‐test for precision. A reaction pathway was also proposed. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

18.
The potential of the chlorophyll fluorescence technique in screening for frost sensitivity in a range of Trifolium species from different geographical origins was assessed by measuring the decrease in variable chlorophyll fluorescence (Fvar) of leaves after freezing at - 5°C for 60 min. The method was rapid and the results obtained agreed well with a visual assessment of freezing injury carried out after leaves were returned to optimal growth conditions for 72 h. Trifolium alexandrinum (Berseem clover) cv. Tabor originating from Israel was shown to be the most frost sensitive species studied and Trifolium subterraneum (subterranean clover) cv. Mt. Barker, from temperate regions of Australia, the most frost resistant. On extended periods of freezing, frost damage increased and this was associated with a further reduction in variable chlorophyll fluorescence and in quenching capacity of the thylakoid membranes. These results thus indicate that substantial thylakoid membrane dysfunction is induced at freezing temperatures. Furthermore, it was found that frost hardening of the frost sensitive species T. alexandrinum for 21 days at 5°C reduced the extent of damage sustained by the thylakoid membranes as shown by higher fluorescence quenching capacity, smaller reduction in variable fluorescence (Fvar) and higher initial fluorescence (Fo) when leaves of hardened plants were frozen at -5°C and -7°C.  相似文献   

19.
Water‐soluble glutathione (GSH)‐capped core/shell CdTe/CdS quantum dots (QDs) were synthesized. In pH 5.4 sodium phosphate buffer medium, the interaction between GSH‐CdTe/CdS QDs and sanguinarine (SA) was investigated by spectroscopic methods, including fluorescence spectroscopy and ultraviolet‐visible absorption spectroscopy. Addition of SA to GSH‐CdTe/CdS QDs results in fluorescence quenching of GSH‐CdTe/CdS QDs. Quenching intensity was in proportion to the concentration of SA in a certain range. Investigation of the quenching mechanism, proved that the fluorescence quenching of GSH‐CdTe/CdS QDs by SA is a result of electron transfer. Based on the quenching of the fluorescence of GSH‐CdTe/CdS QDs by SA, a novel, simple, rapid and specific method for SA determination was proposed. The detection limit for SA was 3.4 ng/mL and the quantitative determination range was 0.2–40.0 µg/mL with a correlation coefficient of 0.9988. The method has been applied to the determination of SA in synthetic samples and fresh urine samples of healthy human with satisfactory results. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

20.
We studied changes in the chlorophyll (Chl) fluorescence components in chilling-stressed sweet potato (Ipomoea batatas L. Lam) cv. Tainung 57 (TN57, chilling-tolerant) and cv. Tainung 66 (TN66, chilling-susceptible). Plants under 12-h photoperiod and 400 μmol m−2 s−1 irradiance at 24/20 °C (day/night) were treated by a 5-d chilling period at 7/7 °C. Compared to TN66, TN57 exhibited a significantly greater basic Chl fluorescence (F0), maximum fluorescence (Fm), maximum fluorescence yield during actinic irradiation (Fm′ ), and the quantum efficiency of electron transport through photosystem 2, PS2 (ΦPS2). Chilling stress resulted in decrease in the potential efficiency of PS2 (Fv/Fm), ΦPS2, non-photochemical fluorescence quenching (NPQ), non-photochemical quenching (qN), and the occurrence of chilling injury in TN66. Chilling increased the likelihood of photoinhibition, characterized by a decline in the Chl fluorescence of both cultivars, and photoinhibition during low temperature stress generally occurred more rapidly in TN66.  相似文献   

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