Formation Of Association Complex Research Articles

Determination of glycyrrhizic acid as sweeteners by dual-wavelength overlapping resonance Rayleigh scattering

This study used cationic dyes methyl violet (MV) and neutral red (NR) as probes, based on dual-wavelength overlapping resonance Rayleigh scattering (RRS), and designed two highly sensitive methods for the determination of the natural sweetener glycyrrhizic acid (GZA). In the Clark-Lubs buffer solution, when only MV or NR was present in the solution, they formed supramolecular polymers through hydrogen bonding. When adding GZA at different concentrations, the formation of ionic association complexes led to a subsequent decrease in RRS intensity at two wavelengths in the MV − GZA system and NR − GZA system, and the amount of the decline was proportional to the GZA concentration. The linear ranges were determined as 0.1 − 0.6 mg/L and 0.1 − 0.7 mg/L, with correlation coefficients of 0.9972 and 0.9996, and limits of detection were 0.052 mg/L and 0.016 mg/L, respectively. For this study, reaction conditions were optimized, potential interfering substances were investigated, and the mechanisms behind RRS generation and intensity decrease were discussed. The proposed methods were sensitive, fast, time-saving and efficient, and have been successfully applied to licorice and dried ginger decoction analysis, yielding satisfactory results.

Assay of Tretinoin using Safranine-O as a Chromogenic Reagent in Bulk and Dosage Forms

A new, economical and accurate analytical technique was developed for the assay of tretinoin (TTN) in bulk and formulations. While developing the method, it was found that the reaction was carried out due to the formation of ion-pair association complex involving the carboxyl group in the side chain of the TTN with safranine-O. The colored species formined was stable up to 60 minutes. The optical density of color species was measured at 520 nm. All the variables were optimized. The linearity range lies for the developed method within the concentration ranges of 2-10 μg mL-1.The linear correlation coefficient (r) and molar absorptivity (ϵmax)values were found as 0.9999 and 1.66 x 104 L mol–1cm–1. Percentage recoveries were found from 99.2 ± 1.8 to 100.2 ± 0.7.The method was validated as per ICH guidelines.

Spectrophotometric Determination of Domperidone Maleate, Carvedilol, Dimetindene Maleate and Cinnarizine in Pharmaceuticals by Ion Association Complex Formation with Erythrosine B Dye

Spectrophotometric Determination of Domperidone Maleate, Carvedilol, Dimetindene Maleate and Cinnarizine in Pharmaceuticals by Ion Association Complex Formation with Erythrosine B Dye

Extraction for Mo(VI), W(VI) and Mn(VII) as Oxyanions by Incorporation Cloud Point with Liquid Ion Exchange Methods

Highly sensitive method for separation and determination of micro amount of oxyanion for Mo(VI), W(VI), and Mn(VII) was performed. It has been done after formation of ion pair association complexes with Safranin as complexing agent including joint cloud point extraction with liquid ion exchange methods in the presence of non-ionic surfactant Triton X–100. The study is based on the values of wavelength of maximum absorbance, λmax= 536, 533, and 534nm respectively. Optimal conditions have been pinpointed high extraction efficiency needed for HCl concentration (1.0, 1.0 and 0.6) M respectively in the presence of 50µg metal ions in 10mL aqueous solutions. Besides, the stoichiometry of probable extracted structure of ion pair complexes was1:1:1 for all extracted complex, in addition to other effective parameters on extraction efficiency in this study.

Resonance Rayleigh scattering approach based on association complex formation with erythrosine B for determination of venlafaxine, application to the dosage form and spiked human plasma.

The interaction of venlafaxine hydrochloride (VLX) with erythrosine B was investigated using a resonance Rayleigh scattering (RRS) spectroscopic technique. In acetate buffer (pH3.4), erythrosine B reacted with VLX to form a 1:1 ion-pair complex with concomitant enhancement in RRS intensity that was measured at 330 nm. In addition, the stability constant and the change in free energy of the reaction were estimated. Based on this interaction a new method was developed for a sensitive VLX analysis using erythrosine B as a probe. The results indicated that this method had good selectivity in the presence of coexisting compounds. The scattering intensity (ΔIRRS ) was linearly dependent on VLX concentration over the range 0.04-1.0μg ml-1 with a determination coefficient (r) of 0.9998. The limit of detection and limit of quantitation were 0.01 and 0.03 μg ml-1 , respectively. This method could be suitably used for analysis of VLX in pharmaceutical capsules and human plasma.

Interaction of fungal lipase with potential phytotherapeutics.

Interaction of thymol, carvacrol and linalool with fungal lipase and Human Serum Albumin (HSA) have been investigated employing UV-Vis spectroscopy Fluorescence and Circular dichroism spectroscopy (CD) along with docking studies. Thymol, carvacrol and linalool displayed approximately 50% inhibition at 1.5 mmol/litre concentrations using para-nitrophenyl palmitate (pNPP). UV-Vis spectroscopy give evidence of the formation of lipase-linalool, lipase-carvacrol and lipase—thymol complex at the ground state. Three molecules also showed complex formation with HSA at the ground state. Fluorescence spectroscopy shows strong binding of lipase to thymol (Ka of 2.6 x 109 M-1) as compared to carvacrol (4.66 x 107 M-1) and linalool (5.3 x 103 M-1). Number of binding sites showing stoichiometry of association process on lipase is found to be 2.52 (thymol) compared to 2.04 (carvacrol) and 1.12 (linalool). Secondary structure analysis by CD spectroscopy results, following 24 hours incubation at 25°C, with thymol, carvacrol and linalool revealed decrease in negative ellipticity for lipase indicating loss in helical structure as compared with the native protein. The lowering in negative ellipticity was in the order of thymol > carvacrol > linalool. Fluorescence spectra following binding of all three molecules with HSA caused blue shift which suggests the compaction of the HSA structure. Association constant of thymol and HSA is 9.6 x 108 M-1 which along with ‘n’ value of 2.41 suggests strong association and stable complex formation, association constant for carvacrol and linalool was in range of 107 and 103 respectively. Docking results give further insight into strong binding of thymol, carvacrol and linalool with lipase having free energy of binding as -7.1 kcal/mol, -5.0 kcal/mol and -5.2 kcal/mol respectively. To conclude, fungal lipases can be attractive target for controlling their growth and pathogenicity. Employing UV-Vis, Fluorescence and Circular dichroism spectroscopy we have shown that thymol, carvacrol and linalool strongly bind and disrupt structure of fungal lipase, these three phytochemicals also bind well with HSA. Based on disruption of lipase structure and its binding nature with HSA, we concluded thymol as a best anti-lipase molecule among three molecules tested. Results of Fluorescence and CD spectroscopy taken together suggests that thymol and carvacrol are profound disrupter of lipase structure.

Two facile approaches based on association complex with erythrosine-B for nano-level analysis of duloxetine: application to content uniformity.

Duloxetine is an antidepressant that exhibits its action by preventing the reuptake of serotonin and norepinephrine by neurons. In this analytical study, we developed two facile, sensitive methods for duloxetine analysis. Both methods rely on the formation of binary association complex between erythrosine-B and duloxetine in an acidic medium using spectrofluorimetric and resonance Rayleigh scattering (RRS) techniques. Spectrofluorimetric method simply uses the quenching property of the formed complex on the native fluorescence of erythrosine-B at an emission wavelength of 557.2 nm (λex = 528.6), while RRS is based on detecting the enhancement in the RRS signal at 357.2 nm. The proposed methods have been validated according to the International Conference on Harmonization guidelines. The approaches provide linear assay of duloxetine hydrochloride over 0.1–2.4 µg ml−1 and 0.2–2.0 µg ml−1 for spectrofluorimetric and RRS methods, respectively. Variables affecting methods and complex formation were studied and optimized. The limit of detection values were 0.03 and 0.056 µg ml−1 for spectrofluorimetric and RRS methods, respectively. Both approaches were applied with acceptable results for formulation analysis and evaluation of cymbatex capsule content uniformity.

Cyclodextrin polymers and salts: An Eco-Friendly combination to modulate the removal of sulfamethoxazole from water and its release

This study is aimed to validate water-insoluble cyclodextrin-epichlorohydrin polymer (β-EPI) use to remove, by adsorption, sulfamethoxazole (SMX) from water and then release it via an environmentally friendly treatment so that the adsorbent can be recycled according to one of the objectives of the European Project Life “Clean up” (LIFE 16 ENV/ES/000169).SMX adsorption experiments on β-EPI polymer in-batch were performed, varying different experimental parameters of the process, such as contact time, pH values, and so on.The adsorption process, exothermic and driven by enthalpy, occurs both through the formation of inclusion and association complexes, involves mainly hydrophobic and hydrogen bonds, has a rate-controlling step depending on both pollutant concentration and adsorbent dose and can be described by the Freundlich and Dubinin-Radushkevich models which confirm the polymer surface heterogeneity and the physical nature of the adsorption. The presence of salts gives rise to a general decrease in the SMX sorption, mainly in the case of bromide, which was used to promote the SMX desorption and regenerate the adsorbent. The overall results indicate that β-EPI polymer is not only capable of removing SMX by adsorption with short contact times and a qmax = 10 mg/g but it is also easily regenerated using a 0.5 M solution of sodium bromide without any loss in the adsorption performance and with obvious economic and environmental advantages. The polymer as synthesized, with SMX adsorbed and regenerated was characterized by FT-IR, SEM and DSC.

Resonance Rayleigh scattering and spectrofluorimetric approaches for the selective determination of rupatadine using erythrosin B as a probe: application to content uniformity test

In this study, spectrofluorimetric and resonance Rayleigh scattering techniques were applied for the first time for determination of rupatadine through two validated methods. The proposed methods were based on a facile association complex formation between rupatadine and erythrosin B reagent in acidic medium. Spectrofluorimetric determination relied on the quenching effect of rupatadine on the fluorescence intensity of erythrosin B at 556 nm (excitation = 530 nm). Conversely, the resonance Rayleigh scattering (RRS) method relied on enhancement in the resonance Rayleigh scattering spectrum of erythrosin B at 344 nm after the addition of rupatadine. The developed methods produced linear results over ranges 0.15-2.0 μg/ml and 0.1-1.5 μg/ml, with detection limits of 0.030 μg/ml and 0.018 μg/ml for the spectrofluorimetric method and the RRS method, respectively. All reaction conditions for rupatadine-erythrosin B formation were optimized experimentally and both methods were validated according to International Council for Harmonisation guidelines. The developed methods were applied to estimate rupatadine content in its pharmaceutical tablet dosage form with acceptable recoveries. Furthermore, a content uniformity test for the commercial rupatadine tablets was successfully applied by the suggested spectroscopic methods according to United States Pharmacopeia guidelines.

Thermodynamic and Kinetic Studies on Novel Platinum(II) Complex Containing Bidentate N,N-Donor Ligands in Ethanol-Water Medium

Kinetic and mechanistic investigations have been made on the displacement of the two aqua molecules from the complex 1 i.e., [Pt(2,2′-bipyridine)(H2O)2]2+ represented as {Pt(bpy)} (bpy = 2,2′-bipyridine) at pH 4.0. All the substitution reactions have been monitored at 264, 284 & 317 nm respectively where the spectral difference between the reactant and product is maximum. Two consecutive reaction steps were observed for the substitution of aqua molecules with some didentate N- and N-donor ligands namely, dimethylglyoxime (L1H), 1, 2-cyclohexanedionedioxime (L2H) and α-furildioxime (L3H) in ethanol-water medium using variable-temperature and stopped-flow spectrophotometry. Among the two steps, the former is ligand dependent and the later is ligand independent, where chelation observed. All rate and activation parameters are consistent with associative substitution mechanisms. The thermodynamic parameters were also calculated, which gives a negative DG0 value at all temperatures studied, supporting the spontaneous formation of an outer sphere association complex. The products of the reaction have been characterized with the help of IR and ESI-MS spectroscopic analysis.

Indirect Spectrofluorometric Determination of Enoxaparin Sodium in Pharmaceutical Formulation (Injection) by Ion Association Complex Formation with Acriflavine Dye

A simple, sensitive and selective spectrofluorometric method has been developed for the determination of enoxaparin sodium in bulk and dosage forms (injection). The method was based on the quantitative quenching effect of enoxaparin on the native fluorescence of acriflavine due to the formation of nonfluorescent supramolecular ion issociation complex between the studied drug and acriflavine dye in aqueous solution. The decrease of acriflavine fluorescence was observed at 506 nm after excitation at 402 nm. The relationship between quenching fluorescence intensity and concentration of enoxaparin sodium was linear in the range 0.05-20 µg/ml and with correlation coefficient 0.9990 and with LOD and LOQ 0.011 and 0.035 µg/ml respectively. The average recovery was 100.51% and RSD is less than 3.23%. The stoichiometry of enoxaparin to acriflavine was calculated a 1:4. The method was applied successfully to the determination of enoxaparin form injection samples and the results were in a good agreement with certified value and standard addition procedure.

One-pot reaction for determination of Asenapine maleate through facile complex formation with xanthine based dye: Application to content uniformity test.

Asenapine maleate was approved by the FDA for the treatment of schizophrenia and mania or mixed episodes with bipolar I disorder. In the present article, two spectroscopic methods were developed and validated for the determination of asenapine. Both methods depend on association complex formation between xanthine based dye (eosin Y) and the cited drug in acetate buffer pH=3.8. In the spectrophotometric method (method I), the absorbance of the formed complex was estimated at maximum wavelength of 545nm and Beer's law was obeyed in the range of 1-12μgmL-1. The spectrofluorimetric method (method II) depends on measuring the quenching effect of the drug on the native fluorescence of eosin Y at 545nm after excitation at 303nm. The linearity range of method II was 0.4-3.2μgmL-1. The limits of detection were 0.24 and 0.08μgmL-1 for method I and II, respectively. The instructions of ICH were followed to fully validate the developed analytical procedures. The formation constant of the reaction was 3.93×104 while its Gibb's free energy was -2.6×104Jmol-1. Finally, the methods were applied for the analysis of pharmaceutical tablets and for evaluation of their content uniformity.

Theoretical and Experimental Salvation of Nano Copper Sulfate Interacted with 18-crown-6 in Water

Theoretical study of the electronic structure, NonLinear Optical (NLO) properties, and natural bonding orbital (NBO) analysis of 18-crown-6were investigated using Density Functional Theory DFT) calculations at the B3LYP/6-311G (d,p) level of theory. The optimized structure is a nonlinear compound indicated from the dihedral angles. Natural bonding orbital analysis has been analyzed in terms of the hybridization of each atom, natural charges (Core, Valence, and Rydberg), bonding and antibonding orbital's second-order perturbation energy (E(2)). The calculated EHOMO and ELUMO energies of the title molecule can be used to explain the charge transfer in the molecule and to calculate the global properties; the chemical hardness (η), softness(S), global electrophilicity index (w), and electronegativity (χ). The NLO parameters: static dipole moment (µ), polarizability (α), anisotropy polarizability (Δα), first-order hyperpolarizability (βtot) and third-order hyperpolarizability ⟨γ⟩), of the studied molecule have been calculated at the same level of theory.The Molecular Electrostatic Potential (MEP) and ElectroStatic Potential (ESP) for the title molecule were investigated and analyzed. Also, the electronic absorption spectra were discussed by time-dependent density functional theory (TD-DFT) calculations in ethanol and water solvents. From the experimental conductance measurements, the association thermodynamic parameters (KA, ∆GA, ∆HA, and ∆SA) and complex formation thermodynamic parameters (Kf, ∆Gf, ∆Hf, and ∆Sf) of nano-CuSO4 in presence of 18-crown-6 as a ligand in 10% ethanol-waterer solvents at different temperatures (298.15, 303.15, 308.15 and 313.15K) were applied and calculated.

Xanthene based resonance Rayleigh scattering and spectrofluorimetric probes for the determination of cyclobenzaprine: Application to content uniformity test

Abstract In this work, a resonance Rayleigh scattering technique and a spectrofluorimetric technique were applied to the quantification of cyclobenzaprine through two validated methods. The suggested methods are based on a facile association complex formation between cyclobenzaprine and eosin Y reagent in the acidic medium. The resonance Rayleigh scattering method relied on the enhancement in the resonance Rayleigh scattering spectrum of eosin Y at 370 nm after the addition of cyclobenzaprine. On the other hand, the spectrofluorimetric quantification relied on the quenching effect of cyclobenzaprine on the fluorescence strength of the eosin Y reagent at 545 nm (excitation wavelength at 300 nm). The suggested methods were linear over the ranges of 0.07–1.75 μg/mL and 0.15–2.0 μg/mL with detection limit values of 0.023 μg/mL and 0.048 μg/mL for the resonance Rayleigh scattering method and the spectrofluorimetric method, respectively. All reaction conditions for cyclobenzaprine–eosin Y formation were experimentally evaluated and optimized. In addition, both methods were validated based on ICH rules. Furthermore, the developed methods were practically applied to the analysis of cyclobenzaprine in its commercial tablet dosage form with acceptable recoveries. Moreover, the content uniformity test of the commercial cyclobenzaprine tablets was successfully applied using the proposed spectroscopic methods based on USP rules.

Analytical method for the assay of Perindopril Erbumine in formulations by ion association complex formation using Tropaeolin OOO (TPOOO)

Analytical method for the assay of Perindopril Erbumine in formulations by ion association complex formation using Tropaeolin OOO (TPOOO)

Theoretical Study of 1,4-Dioxane in Aqueous Solution and Its Experimental Interaction with Nano-CuSO4

The electronic structure, Non-Linear Optical (NLO) properties and Natural Bonding Orbital (NBO) analysis of 1,4-dioxane were investigated using the theoretical study of Density Functional Theory (DFT) calculations at the B3LYP/6-311G (d,p) level of theory. The optimized structure is nonlinear as indicated from the dihedral angles. Natural bonding orbital analysis has been analyzed in terms of the hybridization of each atom, natural charges (Core, Valence and Rydberg), bonding and antibonding orbital's second order perturbation energy (E(2)). The calculated EHOMO and ELUMO energies of the title molecule can be used to explain the charge transfer in the molecule and to calculate the global properties; the chemical hardness (η), softness (S) and electronegativity (χ). The NLO parameters: static dipole moment (µ), polarizability (α), anisotropy polarizability (Δα) and first order hyperpolarizability (βtot) of the studied molecule have been calculated at the same level of theory. The Molecular Electrostatic Potential (MEP) and Electro Static Potential (ESP) for 1,4-dioxane were investigated and analyzed. Also, the electronic absorption spectra were discussed by Time-Dependent Density Functional Theory (TD-DFT) calculations for 1,4-dioxane in 10% ethanol/water. From the experimental conductance measurements, the association thermodynamic parameters (KA, ∆GA, ∆HA and ∆SA) and complex formation thermodynamic parameters (Kf, ∆Gf, ∆Hf and ∆Sf) of nano-CuSO4 in the presence of 1,4-dioxane as a ligand in 10% ethanol-water at different temperatures (298.15, 303.15, 308.15 and 313.15 oK) were applied and calculated.

Application of a xanthene dye, eosin Y, as spectroscopic probe in chemical and pharmaceutical analysis; a review

AbstractEosin Y (EY) is an acidic xanthene dye which is mainly used in food stuff and biological staining. Various analytical methods have been reported for the utility of this dye in the quantitative determination of several pharmaceutical compounds, heavy metals in addition to some surfactants and proteins. Most of the applied methods were based on the formation of association complexes between eosin Y and the target analytes in buffered aqueous solutions. The present article represents a comprehensive review for the use of eosin Y as a probe in analytical chemistry.

Mutual Diffusion in Liquid Rubidium–Bismuth Alloys

The mutual diffusion in rubidium–bismuth melts was investigated using a gammaray attenuation technique. The concentration dependence of the interdiffusion coefficient has two maxima in the vicinity of 25 and 50 at.% Bi. The analysis based on Darken’s relation shows that this feature is connected to a tendency for the formation of associated complexes in the liquid alloys.

Studying the association complex formation of atomoxetine and fluvoxamine with eosin Y and its application in their fluorimetric determination.

A simple, sensitive and non-extractive spectrofluorimetric method has been developed and validated for the determination of two psychoanaleptic drugs, atomoxetine and fluvoxamine, in pure forms and pharmaceutical dosage forms. The proposed method is based on the formation of binary complexes between eosin Y and the studied drugs in the presence of a Teorell–Stenhagen buffer. The quenching of the native fluorescence of eosin Y due to complex formation with the studied drugs was measured spectrofluorimetrically at 545 nm after excitation at 302 nm. At the optimum reaction conditions, the fluorescence quenching values (ΔF) and concentrations were rectilinear over the concentration ranges of 0.2–2.2 and 0.3–2.2 µg ml−1 for atomoxetine and fluvoxamine, respectively. The developed method was successfully applied for the determination of the studied drugs in their pharmaceutical formulations with average percentage recoveries of 100.13 ± 0.66 and 99.69 ± 0.44 for atomoxetine and fluvoxamine, respectively (n = 5), without interference from common excipients.

New Conductometric Titration Methods for Determination of Diphenhydramine Hydrochloride Using Sodium Tetraphenylborate and Cetylpyridinium Bromide

Sodium tetraphenylborate (TPB) and cetylpyridinium bromide (CPB) were used as titrant for the conductometric determination of diphenhydramine hydrochloride (DPH) drug through ion association complex formation and then the conductance of the solution is measured as a function of the volume of titrant. The effect of the solvent, reagent concentration, temperature and molar combining ratio of the formed ion-associates were studied and evaluated. The suggested method was applied for the determination of diphenhydramine hydrochloride in pure form and pharmaceutical preparations. The described procedures allowed the determination of the studied drug in bi-distilled water in the range of 0.75–16 mg. Statistical treatment of the experimental results indicates that the method is precise and accurate. The accuracy of the method was indicated by excellent recovery and the precision supported by the low relative standard deviation <1%. The sensitivity of the proposed method was discussed and the results were compared with the potentiometric pharmacopoeial method. The proposed procedure was simple, precise and low cost and can be applied for the routine measurements of the cited drug.