Study on the Interaction Between Verapamil Hydrochloride and Eosin Y by Absorption,Fluorescence and Resonance Rayleigh Scattering Spectra and Their Analytical Applications

In pH 2.8~3.6 HCl-NaAc buffer solution, eosin Y (EY) can react with verapamil hydrochloride(VP) to form a 1:1 ion-association complex, which not only causes the change of absorption spectra and the quenching of fluorescence, but also results in the great enhancement of resonance Rayleigh scattering (RRS). Furthermore, a new RRS spectrum with the maximum wavelength at 324 nm will appear. In this work, the spectral characteristics of absorption, fluorescence and resonance Rayleigh scattering spectra, the optimum conditions for the reaction, the influencing factors and the analytical properties have been investigated. Thereby, a sensitive, simple, rapid and new method for the determination of VP by using eosin Y as a probe has been developed. The detection limit is 0.95 ng/mL for RRS method, 6.4 ng/mL for fluorophotometry and 0.18 μg/mL for spectrophotometric method. The absorbance, RRS and fluorescence intensity is proportional to the concentration of VP in the range of 0.6036~4.0 μg/mL, 0.0032~4.5 μg/mL and 0.0213~4.0 μg/mL, respectively. The effects of the reaction of verapamil hydrochloride and eosin Y on the absorption, fluorescence and resonance Rayleigh scattering spectra have been investigated. Meanwhile, the influences of coexisting substances are tested by RRS method and the results show that this method can be satisfactorily applied to the determination of VP in tablet and human serum samples. The composition and structure of the ion-association complex and the reaction mechanism are discussed. Moreover, the energy transfer among absorption, fluorescence and RRS was investigated briefly in this work.     

Validated Spectroflurimetric Determination of Some H1 Receptor Antagonist Drugs in Pharmaceutical Preparations Through Charge Transfer Complexation

A validated simple, rapid, and selective spectrofluorimetric method was developed for the determination of some antihistaminic H₁ receptor antagonist drugs namely ebastine (EBS), cetirizine dihydrochloride (CTZ), and fexofenadine hydrochloride (FXD). The method is based on the reaction of the cited drugs with some Π acceptors namely p-chloranilic acid (CLA), tetracyanoethylene (TCNE), and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) to give highly fluorescent derivatives. The fluorescence intensity—concentration plots were rectilinear over the concentration ranges of 0.2–3.0, 0.2–2.5 and 0.15–2.0 μg/ml for EBS with CLA, DDQ, and TCNE respectively; 0.5–7.0, 0.5–6.0, and 0.2–4.0 μg/ml for CTZ with the previously mentioned reagents, and 0.2–3.5, 0.5–6.0, and 0.2–3.5 μg/ml for FXD. The factors affecting the formation of the reaction products were carefully studied and optimized. The method was applied for the determination of the studied drugs in their dosage forms. The results obtained were in good agreement with those obtained by the comparison methods. Reactions Stoichiometries of the complexes formed between the studied drugs and Π acceptors were defined by the Job’s method of the continuous variation and found in 1:1 in all cases.     

Simultaneous Determination of Labetalol and Furosemide by First-Derivative Synchronous Spectrofluorimetry

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.     

Spectrofluorometric Determination of Methocarbamol in Pharmaceutical Preparations and Human Plasma

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.     

Synthesis of Functionalized ZnSe Nanoparticles and Their Applications in the Determination of Bovine Serum Albumin

Luminescent quantum dots (QDs)-semiconductor nanocrystals were promising alternative to organic dyes for fluorescence-based applications. In this paper, we developed procedures to use mercaptoacetic acid (MAA) to modify ZnSe nanoparticles and made the nanoparticles to be soluble for the quantitative and selective determination of bovine serum albumin (BSA). Maximum fluorescence intensity was produced at pH 7.0, with excitation and emission wavelengths at 242 and 348 nm, respectively. Under optimal conditions, the straight line equation: ^△ F = 0.38 + 0.34 C (μg/ml) was found between the relative fluorescence intensity and the concentration of BSA in the range of 9.6–124.8 μg/ml, and the limit of detection was 2 μg/ml.     

Application of Functionalized ZnSe Nanoparticles to Determinate Heavy Metal Ions

In this paper, ZnSe nanoparticles, which were modified with mercaptoacetic acid (MAA), worked as novel fluorescence sensors for the quantitative determination of copper(II) and nickel(II). Under the optimal conditions, the fluorescence intensities of functionalized ZnSe nanoparticles were quenched by the addtion of copper(II) or nickel(II) ions, there were linear relationships between the relative fluorescence intensity (logF₀/F) and the concentration in the range of 140–2,000 μg/L for copper(II) (R = 0.9973) and 30–1,000 μg/L for nickel(II) (R = 0.9992), the limits of detection were 50 μg/L and 5 μg/L, respectively.     

Conventional and First Derivative Synchronous Fluorometric Determination of Ethamsylate in Pharmaceutical Preparations and Biological Fluids. Application to Stability Studies

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.     

Study on the Binding Behavior of Lysozyme with Cephalosporin Analogues by Fluorescence Spectroscopy

It was first found that the intrinsic fluorescence of lysozyme at 340 nm can be quenched by cephalosporin analogues through the static quenching and non-radiative energy transferring procedure. In the acetate buffer solution with pH 7.0 and 298 K, the quenching fluorescence intensity was in a good linearity over the concentration of drugs in the range of 1–100 μmol L⁻¹, 0.1–100 μmol L⁻¹, 0.5–100 μmol L⁻¹ and 0.05–100 μmol L⁻¹ for cefradine, cefuroxime, cefotaxime and ceftriaxone, respectively. The quenching ability or the binding ability of the studied drugs followed the pattern: ceftriaxone > cefotaxime > cefuroxime > cefradine, which was close to the order of their antibacterial ability. The binding parameters including the association constant and the number of binding potential point were calculated at different temperatures (288, 298 and 308 K), and thermodynamic parameters ΔH°, ΔS° and ΔG° were given. The binding mode of lysozyme with cephalosporins showed that the hydrophobic effect might play a major role. The binding distance between cephalosporin and tryptophan residue in lysozyme was obtained. The results provided the quantitative information for the binding of cephalosporin to lysozyme, and it was suggested that the drugs probably bound to the active site near Trp62 in lysozyme.     

Study on the interaction of tropisetron hydrochloride and l-tryptophan by spectrofluorimetry and its analytical application

A new method to determine tropisetron hydrochloride with l-tryptophan in the medium with pH=9.0 was studied, which is based on the fluorescence quenching effect of tropisetron hydrochloride on l-tryptophan. The fluorescence quenching mechanism and various factors influencing fluorescence quenching were discussed. Under the optimum conditions, the linear range and detection limit were 0.03-12.0 and 0.01 μg/mL (correlation coefficient r=0.9970), respectively. The calibration curve equation was ΔF=6.17+12.56 C (μg/mL). RSD was 3.4% (c=4.0 μg/mL, n=5); the detection limit estimated (S/N=3) was 0.01 μg/mL. The proposed method had been successfully applied to determine tropisetron hydrochloride in real samples and the obtained results were in good agreement with the results of the official method.     

First Derivative Synchronous Fluorescence Spectroscopy for the Simultaneous Determination of Sulpiride and Mebeverine Hydrochloride in Their Combined Tablets and Application to Real Human Plasma

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.     

Fluorescence Quenching Reaction of Polyvinylpyrrolidone-Eosin Y System for the Determination of Polyvinylpyrrolidone

In pH 1.8 ∼ 2.8 weak acid medium, polyvinylpyrrolidone (PVP) and Eosin Y reacted to form complex that could result in Eosin Y (EY) fluorescence quenching. The maximum quenching wavelength was at 542 nm. The fluorescence quenching (ΔF) was proportional to the concentration of polyvinylpyrrolidone in a certain range. The linear range, the correlation coefficient and the detection limit were 0.33 ∼ 2.0 μg•mL⁻¹, 0.9994 and 99.6 ng•mL⁻¹, respectively. The influences of the coexistence substances were tested and the results showed that the method had good selectivity. Therefore, a new method based on fluorescence quenching of eosin Y by PVP for the determination of trace PVP was developed. The method was sensitive, simple and rapid, which was applied to the determination of trace PVP in the beer with satisfactory results. The reaction mechanism was also discussed.     

Spectrofluorimetric Determination of Etodolac, Moxepril HCl and Fexofenadine HCl Using Europium Sensitized Fluorescence in Bulk and Pharmaceutical Preparations

A simple, selective and sensitive luminescence method has been developed for the assay of etodolac (I), moxepril HCl (II) and fexofenadine HCl (III) in bulk drug and pharmaceutical formulations. The method is based on the luminescence sensitization of europium (Eu³⁺) by complexation with the studied drugs. The fluorescence intensities of the products were measured at 667 nm for (I) and at 615 for (II) and (III) while exciting at 276 for all the studied drugs. The fluorescence intensity was directly proportional to the concentration over the range (20–280), (40–240) and (30–80) ng/ml with limits of detection (LOD) = 0.93, 0.92 and 0.95 μg/ml for drugs I, II and III respectively. Optimum conditions for the formation of the complex in methanol were carefully studied. The proposed method was successfully applied for the assay of the studied drugs in pharmaceutical formulations with excellent recovery.     

Micelle-Enhanced Spectrofluorimetric Method for Determination of Cholesterol-Reducing Drug Ezetimibe in Dosage Forms

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.     

Validated spectrophotometric method for the determination,spectroscopic characterization and thermal structural analysis of duloxetine with 1,2-naphthoquinone-4-sulphonate

A novel, selective, sensitive and simple spectrophotometric method was developed and validated for the determination of the antidepressant duloxetine hydrochloride in pharmaceutical preparation. The method was based on the reaction of duloxetine hydrochloride with 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline media to yield orange colored product. The formation of this complex was also confirmed by UV-visible, FTIR, ¹H NMR, Mass spectra techniques and thermal analysis. This method was validated for various parameters according to ICH guidelines. Beer’s law is obeyed in a range of 5.0–60 μg/mL at the maximum absorption wavelength of 480 nm. The detection limit is 0.99 μg/mL and the recovery rate is in a range of 98.10–99.57%. The proposed methods was validated and applied to the determination of duloxetine hydrochloride in pharmaceutical preparation. The results were statistically analyzed and compared to those of a reference UV spectrophotometric method.     

盐酸丁卡因与赤藓红的荧光猝灭反应及其分析应用

在pH 4.0的弱酸性介质中,盐酸丁卡因(TA·HCl)与赤藓红(ET)形成1∶1的离子缔合物,导致赤藓红溶液荧光猝灭。当分别于最大激发/最大发射(λ_ex/λem)525 nm/556 nm进行测量时,荧光猝灭值(ΔF)与TA·HCl浓度在0.28～4.8 μg·mL-1范围呈良好的线性关系。该方法灵敏度高,检出限为0.083 μg·mL-1。考察了共存物质的影响,表明方法有良好的选择性。据此发展了一种高灵敏、简便快速测定微量TA·HCl的新荧光分光光度法。该法用于人血清及尿样中盐酸丁卡因的含量测定,结果满意。文章还研究了反应体系的荧光特性,并结合量子化学AM1计算对荧光猝灭机理进行了讨论。     

Reductive Fluorescence Quenching of the Photoexcited Free Base <Emphasis Type="Italic">meso</Emphasis>-Tetrakis (Pentafluorophenyl) Porphyrin by Amines

Steady state and time resolved fluorescence quenching behaviors of meso-Tetrakis (pentafluorophenyl) porphyrin (H₂F₂₀TPP) in presence of different aliphatic and aromatic amines have been executed in homogeneous dichloromethane (DCM) solution. At room temperature in DCM, free base (H₂F₂₀TPP) shows fluorescence with two distinct peaks at 640 and 711 nm and natural lifetime τ _f = 9.8 ns which are very similar to that of meso-tetraphenyl porphyrin (TPP). Unlike TPP, addition of both aliphatic and aromatic amines to a solution containing H₂F₂₀TPP results in an efficient decrease in fluorescence intensity without altering the shape and peak position of fluorescence emission. Upon addition of amines there was no change in optical absorption spectra of H₂F₂₀TPP. The fluorescence quenching rate constants ranged from 1 × 10⁹ to 4 × 10⁹ s⁻¹, which are one order below to the diffusion control limit, and temperature dependent quenching rate constants yield the activation energies which are found to be order of 0.1 eV. Femto second transient absorption studies reveal the existence of amine cation radical and porphyrin anion radicals with very short decay time (15 ps). The fluorescence quenching reaction follows Stern–Volmer kinetics. Steady state and time-resolved data are interpreted within general kinetic scheme of Marcus semi-classical model which attributes bimolecular electron transfer process between amines and the lowest excited singlet state of H₂F₂₀TPP. Calculated internal reorganization energies are found to be in between 0.04 and 0.22 ev. Variation of electron transfer rate as function of free energy change (∆G⁰) points the ET reactions in the present systems are in Marcus normal region. This is the first example of reductive fluorescence quenching of free base neutral porphyrins in homogeneous organic solvent ever known.     

CORAL: QSPR models for solubility of [C60] and [C70] fullerene derivatives

Quantitative structure–property relationships (QSPRs) between the molecular structure of [C₆₀] and [C₇₀] fullerene derivatives and their solubility in chlorobenzene (mg/mL) have been established by means of CORAL (CORrelations And Logic) freeware. The CORAL models are based on representation of the molecular structure by simplified molecular input line entry system (SMILES). Three random splits into the training and the external validation sets have been examined. The ranges of statistical characteristics of these models are as follows: n = 18, r ² = 0.748–0.815, s = 15.1 –17.5 (mg/mL), F = 47–71 (training set); n = 9, r ² = 0.806–0.936, s = 12.5–17.5 (mg/mL), F = 29–103 (validation set).     

Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria

Copper (II) oxide multi-armed nanoparticles composed of 500–1000 nm long radiating nanospicules with 100–200 nm width near the base and 50–100 nm width at the tapered ends and ~25 nm thickness were synthesized by electrochemical deposition in the presence of an oxidant followed by calcination at 150 °C. The nanoparticles were characterized using SEM/EDX for morphology and composition, Raman spectroscopy for compound identification, and broth culture method for antibacterial efficacy. The CuO nanoparticles have shown remarkable bactericidal efficacy against Gram-positive and -negative waterborne disease causing bacteria like Escherichia coli, Salmonella typhi, staphylococcus aureus and Bacillus subtilis. E. coli has been chosen as representative species for waterborne disease causing bacteria. In antibacterial tests 500 μg/mL nano CuO killed 3 × 10⁸ CFU/mL E. coli bacteria within 4 h of exposure. Moreover, 8.3 × 10⁶ CFU/mL E. coli were killed by 100 and 10 μg/mL nano CuO within 15 min and 4 h of exposure, respectively. Antibacterial activity of nano CuO has been found many-fold compared with commercial bulk CuO. The fate of nanoparticles after antibacterial test has also been studied. The synthesized CuO nanoparticles are expected to have potential antibacterial applications in water purification and in paints and coatings used on frequently touched surfaces and fabrics in hospital settings.     

Immunological impact of magnetic nanoparticles (Ferucarbotran) on murine peritoneal macrophages

Ferucarbotran, a clinically used superparamagnetic iron oxide, is widely developed as a magnetic resonance imaging (MRI) contrast agent and has the potential to improve the monitoring of macrophage recirculation in vivo. However, the biological effect of Ferucarbotran or magnetic nanoparticles (MNPs) on macrophage is not clearly understood yet. This study is aimed to examine the immunological impact of Ferucarbotran toward murine peritoneal macrophages. Cells treated with Ferucarbotran demonstrated a dose–responsive increase of granularity in the cytoplasm. After 24 h of incubation, viability and cytotoxicity in macrophages treated with 200 μg Fe/mL of Ferucarbotran were not affected. Macrophages loaded with Ferucarbotran above 100 μg Fe/mL showed a significant (p < 0.01) increase in cytokine (TNF-α, IL-1β, IL-6) secretion and mRNA expression, followed by nitric oxide (NO) secretion and iNOS mRNA expression. Chemotactic responses of Ferucarbotran-preloaded macrophages toward CX3CL1 were significantly (p < 0.05) lower than those of untreated macrophages. Taking together, Ferucarbotran at high dose (100 μg Fe/mL) could induce murine peritoneal macrophages activation in pro-inflammatory cytokine secretion and NO production.     

Fast Separation Ultra-Performance Liquid Chromatography for Determination of Pre-Column Derivative Abamectin and Ivermectin Residues in Vegetable

A new residue method for quantification of abamectin and ivermectin in vegetable is described in the article. The derivative process is devised that acylating chemical is firstly performed by N-methylimidazole (MI) and trifluoroacetic anhydride (TFAA), then which reacted with hydroxyl function of abamerctin to make fluorescence. The influence of triethylamin (TEA) is examined. Separation is resolute by a short column of 1.7 μm size and operated at high pressure values (10.000 psi). The optimal chromatographic condition and the highest sensitivity are achieved by acetonitrile: water (95: 5), 0.4 mL/min, 0.2 μL injector. The detection limits of abamectin and ivermectin are 1 μg/kg respectively.