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1.
Two simple, accurate and highly sensitive spectrofluorometric methods were developed for the determination of ethamsylate
(ETM). Method I is based on measuring the native fluorescence of ethamsylate in water at 354 nm after excitation at 302 nm.
The calibration plot was rectilinear over the range of 0.05–1 μg/mL for ETM with limits of detection and quantitation of 7.9
and 26 ng/mL, respectively. Method II involved synchronous and first derivative synchronous fluorometric methods for the simultaneous
determination of ethamsylate (ETM) and hydroquinone (HQ) which is considered as an impurity and/or acidic degradation product.
The synchronous fluorescence of both the drug and its impurity were measured in methanol at Δ λ of 40 nm. The peak amplitudes
(1D) were estimated at 293.85 or 334.17 nm for ETM and at 309.05 nm for HQ. Good linearity was obtained for ETM over the ranges
0.1–1.4 μg/mL and 0.1–1.0 μg/mL at 293.85 and 334.17 nm, respectively. For HQ, the calibration plot was rectilinear over the
range of 0.01–0.14 μg/mL at 309.05 nm. Limits of detection were 20, 2.01 ng/mL and limits of quantitation were 60, 6.7 ng/mL
for ETM and HQ by method II, respectively. Both methods were successfully applied to commercial ampoules and tablets. The
results were in good agreement with those obtained by the reference method. Method I was utilized to study the stability of
ETM and its degradation kinetics using peroxide. The apparent first-order rate constant, half-life times and activation energy
of the degradation process were calculated. Method I was further extended to the in-vitro and in-vivo determination of ETM
in spiked and real plasma samples. The mean% recoveries were 99.57 ± 3.85 and 89.39 ± 5.93 for spiked and real human plasma,
respectively. 相似文献
2.
M. Walash M. Sharaf El-Din Nahed El-Enany M. Eid Sh. Shalan 《Journal of fluorescence》2010,20(6):1275-1285
A rapid, simple and highly sensitive first derivative synchronous fluorometric method has been developed for the simultaneous
analysis of binary mixture of sulpiride (SUL) and mebeverine hydrochloride (MEB). The method is based upon measurement of
the synchronous fluorescence intensity of these drugs at ∆λ = 100 nm in water. The different experimental parameters affecting
the fluorescence of the two drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear
over the range of 0.05–1 μg/mL and 0.2–3.2 μg/mL for SUL and MEB respectively with lower detection limits (LOD) of 0.006 and
0.01 μg/mL and quantification limits (LOQ) of 0.0.02 and 0.05 μg/mL for SUL and MEB, respectively. The proposed method was
successfully applied for the determination of the two compounds in synthetic mixtures and in commercial tablets. The high
sensitivity attained by the proposed method allowed the determination of both of SUL and MEB metabolite (veratic acid) in
real human plasma samples applying second derivative synchronous fluorometric technique. The mean% recoveries (n = 3) for both MEB metabolite (veratic acid) and SUL were 99.82 ± 2.53 and 98.84 ± 6.20 for spiked human plasma respectively,
while for real human plasma, the mean% recoveries (n = 3) were 91.49 ± 4.25 and 91.36 ± 8.46 respectively. 相似文献
3.
D. R. El-Wasseef D. T. El-Sherbiny M. A. Abu-El-Enein S. M. El-Ashry 《Journal of fluorescence》2009,19(5):817-828
A rapid, simple and highly sensitive first derivative synchronous spectrofluorimetric method was developed for the simultaneous
analysis of a binary mixture of labetalol HCl (LBT) and furosemide (FUR) without prior separation. The method was based upon
measuring the first derivative of synchronous fluorescence spectra of the two drugs at Δλ =130 nm in aqueous ethanol (55%
V/V). The different experimental parameters affecting the synchronous fluorescence of the studied drugs were carefully studied
and optimized. The first derivative amplitude-concentration plots were rectilinear over the range of 0.10 to 1.00 μg/mL and
0.05–0.50 μg/mL with lower detection limits of 0.0149 and 7×10−3 μg/mL and quantification limits of 0.045 and 0.021 μg/mL for LBT and FUR, respectively. The proposed method was successfully
applied for the determination of the studied drugs in synthetic mixtures. The results obtained were in good agreement with
those obtained by the reference methods. 相似文献
4.
A sensitive time- resolved luminescence method for the determination of meloxicam (MX) in methanol and in aqueous solution
is described. The method is based on the luminescence sensitization of europium (Eu3+) by formation of ternary complex with MX in the presence of 1,10- phenanthroline as coligand, Tween-80 as surfactant and
gadolinium ion as a co-luminescence reagent. The signal for Eu- MX-1, 10- phenanthroline is monitored at λex = 360 nm and λem = 620 nm. Optimum conditions for the formation of the complex in aqueous system were 0.01 M TRIS buffer, pH 8.0, 1,10- phenanthroline
(6.0 × 10−6 M) , Gd3+ (7.0 × 10−6 M), Tween-80 (0.28%) and 1.75 mM of Eu3+ which allows the determination of 20–800 ppb of MX with limit of detection (LOD) of 7 ppb. The relative standard deviations
of the method range between 0.1 and 1.1% indicating excellent reproducibility of the method. The proposed method was successfully
applied for the assay of MX in pharmaceutical formulations, plasma and in urine samples. Average recoveries of 99.8 ± 1.1%,
100.2 ± 0.9% and 100.9 ± 1.1% were obtained for MX in tablet, plasma and urine sample respectively. 相似文献
5.
Ryosuke Nakahara Satomi Kashitani Kumi Hayakawa Yuuki Kitani Takako Yamaguchi Yoshikazu Fujita 《Journal of fluorescence》2009,19(5):769-775
A fluorophotometric method for the determination of hydrogen peroxide (H2O2) using fluorescin was developed. This method was based on the oxidative reaction of fluorescin, a colorless, non-fluorescent
lactoid fluorescein, by H2O2 to give highly fluorescein fluorescence emission. In the determination of H2O2, the calibration curve exhibited linearity over the H2O2 concentration range of 1.5–310 ng mL−1 at an emission wavelength of 525 nm with an excitation of 500 nm and with relative standard deviations (n = 6) of 2.51%, 2.48%, and 1.31% for 3.1 ng mL−1, 30.8 ng mL−1, and for 308 ng mL−1 of H2O2, respectively. The detection limit for H2O2 was 1.9 ng mL−1 six blank determinations was performed (ρ = 6). This proposed method was applied to detection of other reactive oxygen species and nitrogen species (ROS/RNS) such
as singlet oxygen (1O2), hydroxyl radical (•OH), peroxynitrite (ONOO−) etc., and it was possible to detect them with a high sensitivity. In addition, this proposed method was applied to the recovery
tests of H2O2 in calf serum, human saliva, rain water, and wheat noodles; the results were satisfactory. 相似文献
6.
A simple, sensitive and rapid spectrofluorometric method for determination of methocarbamol in pharmaceutical formulations
and spiked human plasma has been developed. The proposed method is based on the measurement of the native fluorescence of
methocarbamol in methanol at 313 nm after excitation at 277 nm. The relative fluorescence intensity-concentration plot was
rectilinear over the range of 0.05–2.0 μg/mL, with good correlation (r = 0.9999), limit of detection of 0.007 μg/ mL and a lower limit of quantification of 0.022 μg/ mL. The described method was
successfully applied for the determination of methocarbamol in its tablets without interference from co-formulated drugs,
such as aspirin, diclofenac, paracetamol and ibuprofen, The results obtained were in good agreement with those obtained using
the official method (USP 30).The high sensitivity of the method allowed the determination of the studied drug in spiked human
plasma with average percentage recovery of 99.42 ± 3.84. 相似文献
7.
In our study, terbium-acetylacetone (Tb-acac) composite nanoparticles have been prepared under vigorous ultrasonic irradiation.
The nanoparticles are water soluble, stable and have extremely narrow emission bands and high internal quantum efficiencies.
They were used as fluorescence probes in the determination of enoxacin (Enox) based on the fluorescence enhancement of nanoparticles
through fluorescence resonance energy transfer (FRET). The influence of buffer solution on the fluorescence intensity was
investigated. Under the optimum conditions, the fluorescence intensity of the Tb-acac-Enox system is linearly proportional
to the Enox concentration in the Enox concentration range of 2 × 10−7–1 × 10−4 M. The correlation coefficient for the calibration curve was 0.9976. The limit of detection as defined by IUPAC, C
LOD = 3S
b/m (where S
b is the standard deviation of the blank signals and m is the slope of the calibration graph) was found to be 3 × 10−8 M. The relative standard deviation (RSD) for six repeated measurements of 1 × 10−4 M Enox was 1.35%. The method was applied to the determination of Enox in pharmaceutical formulation and recovery results
were obtained from urine samples. 相似文献
8.
In this work, a new simple and sensitive flow injection method is developed for the determination of homocysteine with spectrofluorimetric
detection technique. This method is based on the oxidation of homocysteine with Tl (III) in acidic media, producing fluorescence
reagent, TlCl32- (λex = 237 nm, λem = 419 nm). The effects of chemical parameters (including pH of the solutions, the buffer, Tl (III) and potassium chloride
concentrations), instrumental parameters (such as flow rate of the solutions, reaction coil length, and sample loop volume)
and temperature on the fluorescence intensity as an analytical signal are studied and optimized. In the optimum conditions
of the above variables, homocysteine can be determined in the range 4.0 × 10-7–40.0 × 10-6 M with the LDR from 4.0 × 10-7 to 25.0 × 10-6 M. The detection limit (with S/N = 3) is 6.0 × 10-8 M of homocysteine and precision for the injection of 5.0, 10.0 and 15.0 μM of homocysteine are 0.8%, 1.5% and 2.5% (n = 10) respectively. The rate of analysis is 90 samples per hour. The influence of potential interfering substances, including
amino acids and carbohydrates is also studied. The proposed method has been successfully used for the determination of homocysteine
in the real sample (blood serum and tap water) matrix. 相似文献
9.
A simple and sensitive spectrofluorimetric method was developed for the determination of ezetimibe in its pharmaceutical formulations.
The proposed method is based on investigation of the fluorescence spectral behavior of ezetimibe in sodium dodecyl sulfate
(SDS) micellar system. In aqueous solution of acetate buffer pH 5.0, the fluorescence intensity of ezetimibe was greatly enhanced,
200% enhancement, in the presence of SDS. The fluorescence intensity of ezetimibe was measured at 380 nm after excitation
at 268 nm. The fluorescence-concentration plot was rectilinear over the range of 0.03–3.0 μg/mL with lower detection limit
of 3.08 × 10−3 μg/mL. The method was successfully applied to the analysis of ezetimibe in its commercial tablets; the results were in good
agreement with those obtained with the reported method. The application of the proposed method was extended to the stability
studies of ezetimibe after exposure to different forced degradation conditions, such as acidic, alkaline, photo and oxidative
conditions, according to ICH guidelines. 相似文献
10.
A simple, economic, selective, and stability indicating spectrofluorimetric method was developed for the determination of
famotidine (FMT); is based on its reaction with 9, 10-phenanthraquinone in alkaline medium to give a highly fluorescent derivative
measured at 560 nm after excitation at 283 nm. The fluorescence intensity - concentration plot was rectilinear over the concentration
range of 50–600 ng/ml with minimum quantification limit (LOQ) of 13.0 ng/ml and minimum detection limit (LOD) of 4.3 ng/ml.
The factors affecting the development of the fluorescence intensity of the reaction product were carefully studied and optimized.
The method was applied for the determination of FMT in its dosage forms. The stability of the compound was studied, and the
proposed method was found to be stability indicating one. The results obtained were in good agreement with those obtained
by the official method. Furthermore, the method was applied for the determination of FMT in spiked and real human plasma.
The mean % recovery (n = 4) was found to be 99.94 ± 0.24, and 105.13 ± 0.64 for spiked and real human plasma, respectively. The composition of the
reaction product as well as its stability constant was also investigated. Moreover, the method was utilized to investigate
the kinetics of both alkaline and oxidative induced degradation of the drug. The apparent first order rate constant and half
life time of the degradation product was calculated. A proposal of the reaction pathway was postulated. 相似文献
11.
The synthesis and functionalization of carbon nanoparticles with PEG200 and mercaptosuccinic acid, rendering fluorescent carbon dots, is described. Fluorescent carbon dots (maximum excitation and
emission at 320 and 430 nm, respectively) with average dimension 267 nm were obtained. The lifetime decay of the functionalized
carbon dots is complex and a three component decay time model originated a good fit with the following lifetimes: τ
1 = 2.71 ns; τ
2 = 7.36 ns; τ
3 = 0.38 ns. The fluorescence intensity of the carbon dots is affected by the solvent, pH (apparent pK
a of 7.4 ± 0.2) and iodide (Stern-Volmer constant of 78 ± 2 M−1). 相似文献
12.
The binding of quercetin to lysozyme (LYSO) in aqueous solution was investigated by fluorescence spectroscopy, UV-vis absorption
spectroscopy and molecular simulation at pH 7.4. The fluorescence quenching of LYSO by addition of quercetin is due to static
quenching, the binding constants, K
a
, were 3.63 × 104, 3.31 × 104 and 2.85 × 104 L·mol−1 at 288, 298 and 308 K, respectively. The thermodynamic parameters, enthalpy change, ∆H, and entropy change, ∆S, were noted to be −7.56 kJ·mol−1 and 61.07 J·mol−1·K−1. The results indicated that hydrophobic interaction may play a major role in the binding process. The distance r between the donor (LYSO) and acceptor (quercetin) was determined as 3.34 nm by the fluorescence resonance energy transfer.
The synchronous fluorescence spectroscopy showed the polarity around the tryptophan residues increased and the hydrophobicity
decreased. Furthermore, the study of molecular simulation indicated that quercetin could bind to the active site (a pocket
made up of 24 amino-acid residues) of LYSO mainly via hydrophobic interactions and that there were hydrogen interactions between
the residues (Gln 57, Ile 98) of LYSO and quercetin. The accessible surface area (ASA) calculation verified the important
roles of tryptophan (Trp) residues during the binding process. 相似文献
13.
CdHgTe nanoparticles (NPs) with the emission in the near-infrared regions were prepared in aqueous solution, and were characterized
by transmission electron microscopy, X-ray diffraction spectrometry, spectrofluorometry and ultraviolet-visible spectrometry.
Based on the fluorescence quenching of CdHgTe NPs in the presence of proteins, a novel method for the determination of proteins
with CdHgTe NPs as a near-infrared fluorescence probe was developed. Maximum fluorescence quenching was observed with the
excitation and emission wavelengths of 500 and 693 nm, respectively. Under the optimal conditions, the calibration graphs
were linear in the range of 0.04 × 10−6–5.6 × 10−6 g ml−1 for lysozyme (Lyz) and 0.06 × 10−6–6.1 × 10−6 g ml−1 for bovine hemoglobin (BHb), respectively. The limits of detection were 13 ng ml−1 for Lyz and 27 ng ml−1 for BHb, respectively. Four synthetic samples were determined and the results were satisfied. 相似文献
14.
A new, simple and accurate spectrofluorimetric method for the determination of metoclopramide hydrochloride was developed.
The metoclopramide hydrochloride can remarkably enhance the luminescence intensity of the Tb3+ ion doped in PMMA matrix at λex = 360 nm in methanol at pH 6.9. The intensity of the emission band at 545 nm of Tb3+ ion doped in PMMA matrix is increased due to the energy transfer from metoclopramide hydrochloride to Tb3+ in the excited stated. The effect of different parameters, e.g., pH, temperature, Tb3+ concentration, foreign ions that control the fluorescence intensity of the produced ion associate was critically investigated.
The calibration curve of the emission intensity at 545 nm shows linear response of metoclopramide over a concentration range
of 5 × 10−5–5.0 × 10−8 M with detection limit of 8.7 × 10−10 M. The method was used successfully for the determination of metoclopramide in pharmaceutical preparations and human serum.
The average recovery of 99.48% with standard deviation of 0.32% and 96.98% with standard deviation of 0.4%, of pharmaceutical
preparations and human serum respectively, were obtained which compared will with the results obtained from standard LC method
of average recovery 99.04% and standard deviation of 0.6% and average recovery of 98.19% with standard deviation of 0.6% of
pharmaceutical preparations and human serum, respectively. 相似文献
15.
An Immunonanogold Resonance Scattering-Quenching Probe for Rapid and Sensitive Assay of Microalbumin
A novel and sensitive immunonanogold resonance scattering (RS) spectral probe was obtained for rapid detection of microalbumin
(Malb), using 10 nm gold nanaoparticle to label goat anti-human Malb. It was based on that the gold-labeled anti-Malb took
place nonspecific aggregation and exhibited a strong RS peak at 577 nm in pH 5.2 C6H8O7–Na2HPO4 buffer solution containing polyethylene glycol (PEG), and the immunocomplex formed after specific reaction of gold-labeled
anti-Malb with Malb, which led to a decrease in the intensity of RS peak at 577 nm considerably. The decreased RS intensity
at 577 nm (ΔI
577nm) was linear to the concentration of Malb in the range of 4–128 ng/mL, with a detection limit of 3.2 ng/mL. The proposed method
was applied to detect Malb in healthy human urine samples with satisfactory results. 相似文献
16.
Water-soluble Mn2+-doped ZnS quantum dots (QDs) were prepared using mercaptoacetic acid as the stabilizer. The optical properties and structure
features were characterized by X-Ray, absorption spectrum, IR spectrum and fluorescence spectrum. In pH 7.8 Tris-HCl buffer,
the QDs emitted strong fluorescence peaked at 590 nm with excitation wavelength at 300 nm. The presence of sulfide anion resulted
in the quenching of fluorescence and the intensity decrease was proportional to the S2− concentration. The linear range was from 2.5 × 10−6 to 3.8 × 10−5 mol L−1 with detection limit as 1.5 × 10−7 mol L−1. Most anions such as F−, Cl−, Br−, I−, CH3CO2
−, ClO4
−, CO3
2−, NO2
−, NO3
−, S2O3
2−, SO3
2− and SO4
2− did not interfere with the determination. Thus a highly selective assay was proposed and applied to the determination of
S2− in discharged water with the recovery of ca. 103%. 相似文献
17.
Bruno B. Campos Manuel Algarra Joaquim C. G. Esteves da Silva 《Journal of fluorescence》2010,20(1):143-151
A fluorescent hybrid cadmium sulphide quantum dots (QDs) dendrimer nanocomposite (DAB-CdS) synthesised in water and stable
in aqueous solution is described. The dendrimer, DAB-G5 dendrimer (polypropylenimine tetrahexacontaamine) generation 5, a
diaminobutene core with 64 amine terminal primary groups. The maximum of the excitation and emission spectra, Stokes’ shift
and the emission full width of half maximum of this nanocomposite are, respectively: 351, 535, 204 and 212 nm. The fluorescence
time decay was complex and a four component decay time model originated a good fit (χ = 1.20) with the following lifetimes: τ
1 = 657 ps; τ
2 = 10.0 ns; τ
3 = 59.42 ns; and τ
4 = 265 ns. The fluorescence intensity of the nanocomposite is markedly quenched by the presence of nitromethane with a dynamic
Stern-Volmer constant of 25 M−1. The quenching profiles show that about 81% of the CdS QDs are located in the external layer of the dendrimer accessible
to the quencher. PARAFAC analysis of the excitation emission matrices (EEM) acquired as function of the nitromethane concentration
showed a trilinear data structure with only one linearly independent component describing the quenching which allows robust
estimation of the excitation and emission spectra and of the quenching profiles. This water soluble and fluorescent nanocomposite
shows a set of favourable properties to its use in sensor applications. 相似文献
18.
Thioflavin T (ThT) has been widely employed to detect amyloid fibrils in tissues and recently in presence of SDS micelles.
However, the contribution of membranes or micelles to ThT fluorescence has never been investigated. In this paper, we show
for the first time that the anionic micellar microenvironment of SDS has a profound impact on the absorption and fluorescence
spectra of ThT in sharp contrast to cationic (CTAB) and neutral micelles (Triton X-100 & Tween 20). Unlike CTAB or Triton
X-100 or Tween 20 micelles, formation of SDS micelles shifts the λmax for ThT absorption from 412 nm in buffer to 428 nm inside the micelle, with a 28% increase in the peak molar absorptivity
and a ∼13 fold increase in ThT fluorescence (λmax = 489 nm). Extending these observations to cell plasma membranes, we show that ThT can quickly enter and appear selectively
fluorescent inside mammalian cells like BHK21 and HT29, against a dark background owing to negligible fluorescence from free ThT in aqueous medium. The above results suggest that
ThT can be a useful probe for live cell imaging and for selectively labeling micelles on the basis of the charge in the polar
headgroup.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
The interaction between a classic uncoupler (2,4-dinitrophenol, DNP) and bovine serum albumin (BSA) was investigated by fluorescence
spectroscopy under the physiological conditions. The fluorescence quenching constants were calculated by the Stern-Volmer
equation, and based upon the temperature dependence of quenching constants, it was proved that DNP caused a static quenching
of the intrinsic fluorescence of BSA. Owing to the static quenching mechanism, different associative binding constants at
various temperatures were determined and thus the thermodynamic parameters, namely enthalpy (ΔH = −21.12 kJ mol−1) and entropy changes (ΔS = 23.51 J mol−1 K−1) could be calculated based on the binding constants. Moreover, the enthalpy and entropy changes are consistent with the “Enthalpy-Entropy
Compensation” equation obtained from our previous work. The negative enthalpy and positive entropy indicated that the electrostatic
interactions played a major role in DNP-BSA binding process. Site marker competitive displacement experiments were carried
out by using fluorescence and isothermal titration calorimetry (ITC) methods. These results showed that DNP bound with high
affinity to Sudlow’s site I (subdomain IIA) of BSA. The distance (r = 3.78 nm) between donor (BSA) and acceptor (DNP) was obtained according to the mechanism of fluorescence resonance energy
transfer (FRET). Furthermore, the results of synchronous fluorescence and circular dichroism (CD) spectroscopic studies indicated
that the microenvironment and the secondary conformation of BSA were altered. The above results were supported by theoretical
molecular modeling methods. 相似文献
20.
Glutathione capped CdTe quantum dots (QD) were synthesised using a simple experimental procedure and two samples were subjected
of study (QD550 and QD600). The maximum of the excitation and emission spectra and the emission full width of half maximum of these two QD were: QD550, 307, 550 and 37 nm; QD600, 307, 600 and 39 nm. The steady state fluorescence properties of the two QD undergo variation when the pH of the aqueous
solution is varied and are characterised by different apparent pKa: QD550, 5.2 ± 0.1; QD600, 6.3 ± 0.3. The fluorescence intensity of the QD550 is markedly quenched by the presence of micromolar quantities of Pb(II) ion (Stern–Volmer constant of about 7 × 105 M−1). PARAFAC analysis of the excitation emission matrices (EEM) of QD550 acquired as function of the Pb(II) ion showed that only one linearly independent component describes the quenching of the
QD550 by the Pb(II) ion allowing robust estimation of the excitation and emission spectra and of the quenching profiles. 相似文献