19F-nuclear magnetic resonance spectroscopy as a tool to investigate host-guest complexation of some antidepressant drugs with natural and modified cyclodextrins

Purpose: 19F-Nuclear magnetic resonance spectroscopy (19F-NMR) was used to study host-guest complexation of three fluorine containing antidepressant drugs, viz, fluoxetine hydrochloride, citalopram hydrobromide and fluvoxamine maleate, with various cyclodextrins (CD), including α-, β-cyclodextrin, methylated α-cyclodextrin (M-α-CD), diamino derivative of methylated α-cyclodextrin, (DAM-α-CD) and tetramino derivative of methylated α-cyclodextrin (TAM-α-CD).Methods: Using the mole ratio method, a 1:1 stoichiometry was determined for the resulting inclusion complexes. 19F chemical shifts were used to determine the formation constant of the complexes. Experiments were performed with solutions containing 0.001 M drug and various concentrations of CDs. NMR data were plotted as 19F chemical shift versus CD/drug mole ratio, and fitted using the nonlinear least-squares curve fitting program, KINFIT, to obtain the formation constant of CD-drug complex. Molecular modeling (MM) calculations were used to predict the geometry of the complex of fluvoxamine and β-CD. Molecular modeling studies were performed in vacuum phase, employing empirical force fields and semi-empirical quantum theory using AM1 Hamiltonian.Results: Complex formation caused separation of the fluorine peaks that can be assigned to the two enantiomers of fluoxetine hydrochloride. Molecular modeling data suggest that fluvoxamine/β-CD inclusion complexes have a 1:1 stoichiometry and that the CF3-substituted ring of fluvoxamine is embedded in the cavity of β-CD, indicating a good agreement between molecular modeling calculation and experimental data (NMR data).Conclusion: One-dimensional 19F-NMR is a fast and convenient method for the determination of complex stoichiometry and complexation constants of natural and modified CDs and fluorinated drugs.Keywords: Antidepressant drugs, Cyclodextrins, Complexation, Inclusion complex, Formation constant, 19F-NM

Highly selective transport of mercury(II) ion through a bulk liquid membrane

In this work carrier-facilitated transport of mercury(II) against its concentration gradient from aqueous 0.04 M hydrochloric acid solution across a liquid membrane containing isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl]ethane thioate (IIDE) as the mobile carrier in chloroform has been investigated. Sodium thiocyanate solution (1.6 M) was the most efficient receiving phase agent among several aqueous reagents tested. Various parameters such as investigated. Under optimum conditions the transport of Hg(II) across the liquid membrane is more than 97% after 2.5 h. The carrier, IIDE, selectively and efficiently could able to transport Hg (II) ions in the presence of other associated metal ions in binary systems

Design of a Selective and Sensitive PVC-Membrane Potentiometric Sensor for Strontium Ion Based on 1,10-Diaza-5,6-benzo-4,7-dioxacyclohexadecane-2,9-dioneas a Neutral Ionophore

A novel PVC membrane sensor for the Sr2+ ion based on 1,10-diaza-5,6-benzo-4,7- dioxacyclohexadecane-2,9-dione has been prepared. The sensor possesses a Nernstian slope of 30.0 ± 0.6 mV decade-1 over a wide linear concentration range of 1.6 × 10-6-3.0 ×10-3 M with a detection limit of 6.3 ×10-7 M. It has a fast response time of less than 15 s and can be used for at least two months without any considerable divergence in potential. The potentiometric response is independent of the pH of test solution in the pH range 4.3-9.4. The proposed electrode shows good selectivities over a variety of alkali, alkaline earth, and transition metal ions

A liquid membrane system containing dibenzyldiaza-18-crown-6 for selective and efficient transport of silver ions

594-597Dibenzyldiaza-18-crown-6 has been used as a highly efficient and selective carrier for uphill transport of silver ion through a chloroform bulk liquid membrane, in the presence of picrate ion as a suitable counter anion. The selectivity and efficienci of Ag+ transport from aqueous solutions containing other cations such as Tl+, Mg2+, Ca2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd +, Pb2+, Hg2+ and Cr3+ have been investigated. The liquid membrane system is used for the recovery of silver ion from a developed radiological film and a silver solder sample

Spectroscopic Studies on Charge-Transfer Complexation of Iodine with Dibenzo-15-crown-5 and Benzo-12-crown-4 in Chloroform, Dichloromethane and 1,2-Dichloroethane

The formation of charge-transfer complexation between dibenzo-15-crown-5 (DB15C5) and benzo-12-crown-4 (B12C4) (Donor) and iodine is investigated spectrophotometrically in three chlorinated solvents, chloroform, dichloromethane (DCM) and 1,2-dichloroethane (DCE) solution at 25°C. The change in polarity of the solvent also doesn't affect the stoichiometry of the complexes. Values of formation constants reflect the order of ionization potentials of the donors. The observed time dependence of the charge-transfer band and subsequent formation of I3-ion are related to the slow formation of the initially formed 1:1 Donor.I2 outer complex to an inner electron donor-acceptor (EDAr) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion, as follows: Donor + I2 → Donor. I2 (outer complex), fast Donor.I2 (outer complex) → (Donor. I+)I-(inner complex), slow (Donor . I+)I-(inner complex) + I2 → (Donor .I+)I3-, fast The pseudo-first-order rate constants for the transformation process were evaluated in different solvent systems. The stability constants of the resulting EDAr complexes were also evaluated and the solvent effect on their stability are discussed. The resulting complexes were isolated and characterized by FTIR and 1H-NMR spectroscopy

Quantitative Structure-Electrochemistry Relationship Study of Some Organic Compounds Using PC-ANN and PCR

Motivation. A QSPR analysis has been conducted on the half-wave reduction potential (E1/2) of a diverse set of organic compounds by means of principal component regression (PCR) and principal component-artificial neural network (PC-ANN) modeling method. Genetic algorithm was employed as a factor selection procedure for both modeling methods. The results were compared with two other factor selection methods namely eigen-value ranking (EV) and correlation ranking (CR) procedures. Method. By using the Dragon software more than 1000 structural descriptors were calculated for each molecule. The descriptor data matrix was subjected to principal component analysis and the most significant principal components (PC) were extracted. Multiple linear regression and artificial neural network were employed for the respective linear and nonlinear modeling between the extracted principal components and E1/2. First, the principal components were ranked by decreasing eigen-values and entered successively to each modeling method separately. In addition, the factors were ranked by their corresponding correlation (linear correlation for PCR and nonlinear correlation for PC-ANN models) with the half-wave potentials and entered to the models. Finally, genetic algorithm (GA) was also employed to select the best set of factors for both models. Results. The 96 % of variances in the descriptor data matrix could be explained by 30 first extracted PCs. Amon

Metal ion promoted degradation mechanism of chlorpyrifos and phoxim

This study evaluate the degradation of the two organophosphorus pesticides: chlorpyrifos and phoxim in the presence of Ag+ at fixed initial concentration and temperature. Chlorpyrifos and phoxim were used as model compounds to develop experimental methods for the investigation of kinetic and degradation pathways. In order to determine what metabolites will be formed after degradation we used 31P NMR. Chlorpyrifos and phoxim were found to degrade in the presence of Ag+ and the result shown in lower chlorpyrifos to Ag+ ratio (<8), only one product formed and its concentration increased versus time. Degradation of chlorpyrifos and phoxim in methanolic solution in the presence of Ag+ followed first-order exponential decay kinetics, and the half-life (t1/2) of chlorpyrifos and phoxim are 693 and 1155, respectively

Physicochemical studies of the hexadecylpyridinium bromide micellar system in the presence of various concentrations of sodium bromide using a surfactant-selective electrode

1031-1036A membrane electrode selective to hexadecylammonium bromide has been used to study the micellization of the surfactant in the presence of varying amounts of sodium bromide at 27°C. It is found that there is an inverse relationship between the amount of NaBr added and the critical micelle concentration and the degree of counter-ion dissociation of the system studied. The aggregation number of the micelles formed has been determined and found to increase with the concentration of NaBr added. Some evidence for the formation of dimer forms of the surfactant prior to the micelle formation is found at higher concentrations of the electrolyte