Enhanced spectrofluorimetric determination of the pesticide warfarin by means of the inclusion complex with beta-cyclodextrin

The warfarin-beta-cyclodextrin inclusion complex alters the luminescent properties of warfarin. This feature allows the use of a spectrofluorimetric method for its determination that gives improved analytical performance. The spectral changes associated with the inclusion process allowed a value of 160 l mol-1 to be obtained for the complexation constant. Fluorescence intensity is linearly related to warfarin concentration for a quantification limit of from 0.2 to 4 micrograms ml-1. The relative standard deviation at the 1.5 microgram ml-1 level is 3.5%. The method was applied satisfactorily to the determination of warfarin in irrigation water.     

Thermodynamic study on the effects of beta-cyclodextrin inclusion with berberine.

The fluorescence enhancement of berberine (Berb) as a result of complex with beta-cyclodextrin (beta-CD) is investigated. The association constants of alpha-CD and beta-CD with Berb are 60 and 137 M(-1) at 20 degrees C in pH 7.20 aqueous solution. Effects of temperature on the forming inclusion complexes of beta-CD with Berb have been examined through using fluorescence titration. Enthalpy and entropy values calculated from fluorescence data are -33.7 kJ mol(-1) and 74.3 J x mol(-1) K(-1) respectively. It was found that the dielectric constant of beta-CD cavity is about 24 in a rough analogy with absolute alcohol. These results suggest that the extrusion of 'high energy water' molecules from the cavity of beta-CD and hydrophobic interaction upon the inclusion complex formation are the main forces of the inclusion reaction. Effect of pH on the association of beta-CD with Berb was also studied. Mechanism of the inclusion of beta-CD with Berb is further studied by absorption and NMR measurements. Results show that beta-CD forms a 1:1 inclusion complex with Berb.     

Complexation study of diclofenac with beta-cyclodextrin and spectrofluorimetric determination

The inclusional complexation between the anti-inflammatory pharmaceutical diclofenac and beta-cyclodextrin (beta-CD) was studied by potentiometry, spectrophotometry and spectrofluorimetry, in both acid and neutral pH. Guest-host 1:1 stoichiometries for the complexes in both media were determined, and their equilibrium constants were calculated. The values obtained from the different methods used are in very good agreement and are in the order of 10(3). From the analysis of the pKa value for diclofenac in both the absence and presence of beta-CD (4.84 and 4.90 respectively), it was inferred that in the inclusion complex the carboxylic group is located outside the cavity. Further structural characterization of the inclusate was carried out by means of 1H NMR spectra and AM1 semiempirical calculations. Based on the obtained results, a spectrofluorimetric method for the determination of diclofenac in the presence of beta-CD was developed in the range of 0-5 micrograms ml-1. Better limits of detection (0.03 microgram ml-1) and quantification (0.1 microgram ml-1) were obtained in this latter case with respect to those obtained in the absence of beta-CD. The method was satisfactorily applied to the quantification of diclofenac in pharmaceutical preparations.     

Thermodynamic parameters for the molecular inclusion reactions of some azo compounds with α-cyclodextrin

Molecular inclusion reactions of some azo compounds with -cyclodextrin were studied in aqueous solution by means of a stopped-flow method. The forward rate constants for the inclusion reactions were found to be in the order of 10–10⁴ mol^–1 dm³ s^–1. The thermodynamic activation parameters were also determined firstly in -cyclodextrin system.     

Highly sensitive and selective spectrofluorimetric determination of tolnaftate through the formation of ternary inclusion complex of beta-naphthol/beta-cyclodextrin/anionic surfactant system

An indirect spectrofluorimetric method with high sensitivity and selectivity was developed for the determination of antifungal drug: tolnaftate (TNF), depending on the supramolecualr multirecognition interaction among the anionic surfactant sodium laurylsulfate (SLS), β-cyclodextrin (β-CD) and β-naphthol (ROH). The mechanism of the inclusion was studied and discussed by means of fluorescence spectrum, infra-red spectrograms and ¹HNMR spectroscopy. Results showed that the naphthalene ring of ROH and the hydrophobic hydrocarbon chain of SLS were included into the β-CD's cavity to form a ROH:SLS:β-CD ternary inclusion complex with stoichiometry of 1:1:1 at room temperature, which provided effective protection for the excited state of ROH. At λ_ex/λ_em = 273/360 nm, the fluorescence intensity was linear over a tolnaftate concentration range of 2.46 × 10⁻⁹ to 2.10 × 10⁻⁶ mol L⁻¹. The detection limit and relative standard deviation was 7.50 × 10⁻¹⁰ mol L⁻¹ and 1.4%, respectively. The interference of 31 foreign substances was slight. The proposed method had been successfully applied to the determination of tolnaftate in artificial mixed samples with almost quantitative recovery.     

Global and distribution analysis of fluorescence decays and spectrofluorimetric determination of stoichiometry and association constant of the inclusion complex of 2-amino-5,6-dimethyl-benzimidazole with beta-cyclodextrin

The steady state and time-resolved fluorescence study of 2-amino-5,6-dimethyl-benzimidazole (ADBI) have been studied in aqueous solution of β-cyclodextrin (β-CD). The fluorescence decays were analyzed by global analysis and distribution analysis in order to get insight about the inclusion process. The fluorescence lifetime of ADBI is increased in β-CD and an enhancement of the emission, is observed, together with negligible changes in the energy of ADBI in β-CD. The experimental data show that β-CD reacts with ADBI to form a 1:1 host-guest complex with association constant was determined to be 2074±77 M⁻¹. Both global analysis and distribution analysis of the fluorescence decays support the formation of only 1:1 inclusion complex. AM1 calculation shows that the size of ADBI was appropriate for good insertion within the β-CD cavity and the inclusion of ADBI inside the β-CD cavity should takes place from the side of the amino group substituent.     

Resonance Rayleigh scattering technology as a new method for the determination of the inclusion constant of beta-cyclodextrin

The interaction of procaine hydrochloride and beta-cyclodextrin in aqueous solution was studied using resonance Rayleigh scattering technology. The molar ratio of the inclusion complex was 1:1 established by spectrophotometry. The resonance Rayleigh scattering technology was first applied in the determination of the beta-cyclodextrin inclusion constant. The inclusion constant of procaine hydrochloride beta-cyclodextrin complex Kf is 1.23 x 10(2) and 1.27 x 10(2) l mol(-1) for method I and 1.15 x 10(2) and 1.21 x 10(2) l mol(-1) for method II. These determination results were in correspondence with the results of the spectrophotometric and fluorescence methods. Therefore, the resonance Rayleigh scattering method can be used as a new technology for the determination of the inclusion constant.     

Structural determination of midazolam/beta-cyclodextrin inclusion complex by an already proposed protocol and molecular docking studies by quantitative analysis

Structural Chemistry - A lot of interest has been seen in computational methods that provide higher degree of accuracy and reliability, in structural determination and intermolecular interaction of...     

Study on inclusion interaction of piroxicam with beta-cyclodextrin derivatives

The inclusion behavior of piroxicam (PX) with beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and carboxymethyl-beta-cyclodextrin (CM-beta-CD) was investigated by using steady-state fluorescence and nuclear magnetic resonance (NMR) technique. The various factors affecting the inclusion process were examined in detail. The remarkable fluorescence emission enhancement upon addition of CDs suggested that cyclodextrins (CDs) were most suitable for inclusion of the uncharged species of PX. The stoichiometry of the PX-CDs inclusion complexes was 1:1, except for beta-CD where a 1:2 inclusion complex was formed. The formation constants showed the strongest inclusion capacity of beta-CD. NMR showed the inclusion mode of PX with CDs.     

Study on the inclusion complexes of cryptotanshinone with beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin

The inclusion complexes of beta-cyclodextrin (beta-CD) and HP-beta-cyclodextrin (HP-beta-CD) with a kind of tanshinone, cryptotanshinone (CTan) were investigated by using spectrophotometry. Stable inclusion complexes were established in solution and in solid state and were characterized by UV, IR and 1H NMR spectra, respectively. The optimum pH for inclusion is about 7.5. Stoichiometry of the inclusion complex is 1:1. The stabilities of beta-CD and HP-beta-CD to CTan were in the order: beta-CD相似文献   

Simultaneous spectrofluorimetric determination of the rare earths with calcein

The reactivity of the fluorescent reagent calcein with the trivalent cations of the rare earths has been spectrofluorimetrically studied in aqueous solution. Optimum excitation and emission wavelengths were 492-497 and 519-522 nm, respectively. Optimum pH was in the range 6.0-9.2. The stoichiometry of the complexes was 1:1. A direct, rapid and sensitive method for the determination of rare earth mixtures has been proposed with a detection limit of 4.49x10(-8) M and a coefficient of variation of 0.82%.     

A novel spectrofluorimetric method for the determination of DNA

A new simple, selective and sensitive fluorescence quenching method was developed to determine nucleic acids (DNA) with the 9-anthracenecarboxylic acid (ACA)-cetyl trimethyl-ammonium bromide (CTAB) system. The fluorescence intensity of ACA was decreased by the addition (CTAB). However, the fluorescence intensity of the system increased dramatically when DNA was added to the solution. The fluorescence enhancement is probably based on the DNA interaction with CTAB. Under the optimum conditions, the changes of fluorescence intensity in the absence and presence of nucleic acids was proportional to the concentration of nucleic acids over the range 0.08-1.0 microg mL(-1) for CT (calf thymus) DNA or FS (fish sperm) DNA. Its detection limits are 0.02 microg mL(-1) for CT DNA and 0.019 microg mL(-1) for FS DNA. Based on this approach, a new quantitative method for DNA assay is presented in this paper.     

吖啶红动力学荧光法测定痕量甲醛

在H2SO4介质中，以KCIO3-吖啶红为指示反应，建立了测定甲醛的动力学荧光分析法。方法的线性范围为40～600μg／L，检出限为27μg／L。方法用于树脂整理特殊织物和动物标本室内空气中甲醛的测定，与标准方法乙酰丙酮分光光度法进行对照，所测结果经t-检验无显著性差异。     

Interaction of pyromellitic diimide derivatives with beta-cyclodextrin and anthracene-appended beta-cyclodextrin: rim binding vs inclusion complexation

Complex formation of pyromellitic diimide derivatives with beta-cyclodextrin and anthracene-appended beta-cyclodextrin was studied with use of induced circular dichroism and 1H NMR spectroscopies. It is revealed that pyromellitic diimides form rim-binding type complexes with beta-CD and in these complexes the pyromellitic diimides lie just outside of the narrow rim of the CD. With anthracene-appended beta-CD the pyromellitic diimides form true inclusion complexes. Implications of the formation of rim-binding type complexes are also discussed.     

Effect of peracylation of beta-cyclodextrin on the molecular structure and on the formation of inclusion complexes: an X-ray study.

The molecular structures of peracylated beta-cyclodextrins (CDs)--heptakis(2,3,6-tri-O-acetyl)-beta-CD (TA), heptakis(2,3,6-tri-O-propanoyl)-beta-CD (TP), and heptakis(2,3,6-tri-O-butanoyl)-beta-CD (TB)--have been determined by single crystal X-ray structure analysis. Due to the lack of O2...O3' hydrogen bonds between adjacent glucose units of the peracylated CDs, the macrocycles are elliptically distorted into nonplanar boat-shaped structures. The glucose units are tilted with respect to the O4 plane to relieve steric hindrance between adjacent acyl chains. In TB, all glucose units adopt the common (4)C(1)-chair conformation and one butanoyl chain intramolecularly penetrates the cavity, whereas, in TA and TP, one glucose unit each occurs in (O)S(2)-skew-boat conformation and one acyl chain closes the O6 side like a lid. In each of the three homologous molecules the intramolecular self-inclusion and lidlike orientation of acyl chains forces the associated O5-C5-C6-O6 torsion angle into a trans-conformation never observed before for unsubstituted CD; the inclusion behavior of TA, TP, and TB in solution has been studied by circular dichroism spectroscopy with the drug molsidomine and several organic compounds. No inclusion complexes are formed, which is attributed to the intramolecular closure of the molecular cavity by one of the acyl chains.     

Preparation and study on the solid inclusion complex of ciprofloxacin with beta-cyclodextrin

The interaction of ciprofloxacin with beta-cyclodextrin (betaCD) has been studied by several analytical techniques, including 1H-NMR (nuclear magnetic resonance),13C-NMR, fluorescence spectroscopy, infrared (IR) spectroscopy, thermal analysis, and scanning electron microscope. In this paper, solid inclusion complex of ciprofloxacin with beta-CD was synthesized by the coprecipitation method. In addition, the characterization of the inclusion complex has been proved by fluorimetry, IR, differential scanning calorimetry and 1D, 2D NMR. The experimental results confirmed the existence of 1:1 inclusion complex of ciprofloxacin with beta-CD. The formation constant of complex was determined by fluorescence method and 1H-NMR. Spatial configuration of complex has been proposed on two dimensional NMR technique.     

The inclusion compound of a new ionizable derivative of beta-cyclodextrin with ferrocenium drug.

A new beta-cyclodextrin (beta-CD) derivative, mono[6-deoxy-6-(2-butenedinitrile-2,3-dimercapto sodium salt)]-beta-CD (6-mnt-beta-CD), and its inclusion compound with a ferrocenium drug, have been prepared and characterized by IR, UV, 13C-NMR spectroscopy, and mass spectrometry, elemental analysis, thermogravimetry, and cyclic voltammetry (CV). The interplay between the side-arm anion of beta-CD and the ferrocenium (guest) in the inclusion compound 6-mnt-beta-CD-/Fc+ has been investigated by 13C-NMR, UV, IR, and thermogravimetric methods. Charge transfer from the anion to the cation in 6-mnt-beta-CD-/Fc+ was then experimentally identified. The interaction between the guest and the host with side-arm in 6-mnt-beta-CD-/Fc+ resulted in smaller positive potential shifts compared to that in the inclusion compound [beta-CD/Fc+]BF4-.     

Preparation and study on the solid inclusion complex of sparfloxacin with beta-cyclodextrin

The interaction of sparfloxacin with beta-cyclodextrin (beta-CD) has been studied by several analytical techniques, including 1H-NMR, 13C-NMR, fluorescence spectroscopy, infrared spectroscopy, thermal analysis, and scanning electron microscope. In this paper, solid inclusion complex of sparfloxacin with beta-CD was synthesized by the coprecipitation method. In addition, the characterization of the inclusion complex has been proved by fluorimetry, Infrared, differential scanning calorimetry and 1D, 2D NMR. The experimental results confirmed the existence of 1:1 inclusion complex of sparfloxacin with beta-CD. The formation constant of complex was determined by fluorescence method and 1H-NMR. Spacial configuration of complex has been proposed on 2D NMR techniques.     

Determinations of the inclusion complex between gossypol and beta-cyclodextrin

Features of the inclusion complex between gossypol (Gos) and beta-cyclodextrin (CD), such as its aqueous solubility, association constant, characteristics in the solid state and crystalline morphology, as well as the stoichiometry of this complex have been determined. The phase-solubility diagram drawn using UV detections belongs to an AN-type. Fluorescence detection and calculation with the modified Benesi-Hidebrond equation provide an 1:2 stoichiometry for the complex. Its apparent stability constant has been determined to be 3,203 M(-1) by fluorescence technique and confirmed by the calculation from UV spectroscopy. X-ray powder diffractions (XRD) and Scanning Electron Microscopy (SEM) observations showed a clear difference in the crystal morphology of the complex from those of both Gos and beta-CD.