Differential Scanning Calorimetry of Ampicillin-Aspartame Mixture

The possible interaction of anhydrous and trihydrate ampicillin with aspartame, in the solid state, was investigated by comparing the thermal behavior of physical mixtures of the respective original components in different molar ratios, using differential scanning calorimetry. Aspartame was found to form complexes with anhydrous ampicillin and ampicillin trihydrate. These complexes were found to be dependent on the molar ratios of the mixture components. One of the complexes between anhydrous and trihydrate ampicillin and aspartame, as determined from the enthalpy change of the DSC transitions of the mixtures, was found to have a 2:1 molar ratio.     

Differential Scanning Calorimetry of Ampicillin-Aspartame Mixture

Abstract

The possible interaction of anhydrous and trihydrate ampicillin with aspartame, in the solid state, was investigated by comparing the thermal behavior of physical mixtures of the respective original components in different molar ratios, using differential scanning calorimetry. Aspartame was found to form complexes with anhydrous ampicillin and ampicillin trihydrate. These complexes were found to be dependent on the molar ratios of the mixture components. One of the complexes between anhydrous and trihydrate ampicillin and aspartame, as determined from the enthalpy change of the DSC transitions of the mixtures, was found to have a 2:1 molar ratio.     

Studies of Ergotamine Tartrate-Caffeine Interactions by Differential Scanning Calorimetry

Differential scanning calorimetry was used to evaluate the interactions between ergotamine tartrate and caffeine. Physical mixtures of ergotamine tartrate and caffeine, as well as mixtures formed by evaporation of ergotamine tartrate and caffeine from a methanol solution, were evaluated. The preparation and characterization of eleven different molar ratios of ergotamine tartrate-caffeine complexes is described. The drug was found to interact with caffeine in the solid state with the formation of complexes. The mixture obtained from the methanol solution showed complexes with ergotamine tartrate-caffeine molar ratios of 2:3 and 2:15, with possible complexes having 1:10, 1:15 and 1:20 molar ratios. A phase diagram was constructed. Physical mixtures of the same molar ratios showed possible complex formation at molar ratios of 1:1, 1:1 and 1:3.     

Differential Scanning Calorimetry of Cephalexin-Dextrose and Cephalexin-Aspartame Mixtures

The possible interaction of cephalexin with anhydrous dextrose and with aspartame, in the solid state, was investigaged by comparing the thermal behavior of physical mixtures of the respective original components in different molar ratios, using differential scanning calorimetry. Both anhydrous dextrose and aspartame were found to form complexes with cephalexin. The stoichiometries of these complexes were found to be 1:1 molar complexes between cephalexin and anhydrous dextrose and 4:1 and 1:1 molar complexes between cephalexin and aspartame. Complexed cephalexin was found to decompose at markedly lower temperatures than uncomplexed cephalexin.     

Studies of Ergotamine Tartrate-Caffeine Interactions by Differential Scanning Calorimetry

Abstract

Differential scanning calorimetry was used to evaluate the interactions between ergotamine tartrate and caffeine. Physical mixtures of ergotamine tartrate and caffeine, as well as mixtures formed by evaporation of ergotamine tartrate and caffeine from a methanol solution, were evaluated. The preparation and characterization of eleven different molar ratios of ergotamine tartrate-caffeine complexes is described. The drug was found to interact with caffeine in the solid state with the formation of complexes. The mixture obtained from the methanol solution showed complexes with ergotamine tartrate-caffeine molar ratios of 2:3 and 2:15, with possible complexes having 1:10, 1:15 and 1:20 molar ratios. A phase diagram was constructed. Physical mixtures of the same molar ratios showed possible complex formation at molar ratios of 1:1, 1:1 and 1:3.     

Differential Scanning Calorimetry of Cephalexin-Dextrose and Cephalexin-Aspartame Mixtures

Abstract

The possible interaction of cephalexin with anhydrous dextrose and with aspartame, in the solid state, was investigaged by comparing the thermal behavior of physical mixtures of the respective original components in different molar ratios, using differential scanning calorimetry. Both anhydrous dextrose and aspartame were found to form complexes with cephalexin. The stoichiometries of these complexes were found to be 1:1 molar complexes between cephalexin and anhydrous dextrose and 4:1 and 1:1 molar complexes between cephalexin and aspartame. Complexed cephalexin was found to decompose at markedly lower temperatures than uncomplexed cephalexin.     

Thermal Analysis of Cimetidine-Caffeine Complexes

The preparation and characterization of cimetidine-caffeine complexes in the solid state is described. Ten different molar ratios were considered. Complexes were obtained as shown on their DSC thermograms. The heat of transition of these complexes was calculated and found to be dependent on the molar ratio of cimetidine to caffeine. A phase diagram was constructed for these complexes from which a 1:3.25 molar ratio of cimetidine to caffeine was found to exhibit optimum complexation characteristics. The cimetidine endotherms for physical mixtures of the same molar ratios show no significant changes as compared to that of cimetidine alone.     

Differential Scanning Calorimetry of Ampicillin-Dextrose Mixture

The possible interaction of anhydrous ampicillin and ampicillin trihydrate with anhydrous dextrose, in the solid state, was investigated by comparing the thermal behavior, using differential scanning calorimetry, of physical mixtures of the respective original components in different molar ratios. Anhydrous dextrose was found to form complexes with anhydrous ampicillin and ampicillin trihydrate. These complexes were found to be dependent on the molar ratios of the mixture components. The stoichiometries of these complexes were determined from the enthalpy change of the DSC transitions of the mixtures and were found to be 1:1, 2:3 and 1:3 molar complexes between ampicillin, anhydrous and trihydrate, and anhydrous dextrose. Complexed ampicillin was found to decompose at markedly lower temperatures than uncomplexed ampicillin.     

Differential Scanning Calorimetry of Ampicillin-Dextrose Mixture

The possible interaction of anhydrous ampicillin and ampicillin trihydrate with anhydrous dextrose, in the solid state, was investigated by comparing the thermal behavior, using differential scanning calorimetry, of physical mixtures of the respective original components in different molar ratios. Anhydrous dextrose was found to form complexes with anhydrous ampicillin and ampicillin trihydrate. These complexes were found to be dependent on the molar ratios of the mixture components. The stoichiometries of these complexes were determined from the enthalpy change of the DSC transitions of the mixtures and were found to be 1:1, 2:3 and 1:3 molar complexes between ampicillin, anhydrous and trihydrate, and anhydrous dextrose. Complexed ampicillin was found to decompose at markedly lower temperatures than uncomplexed ampicillin.     

Differential Scanning Calorimetry of Aspartame-Mannitol Mixture

Differential scanning calorimetry was used to study both the qualitative and quantitative thermal properties of mixtures of aspartame with both mannitol and granular mannitol. Aspartame was found to be compatible with both forms of mannitol. No aspartame decomposition was observed in the preparation of a fused aspartame-mannitol mixture prepared at 161-165°C. L-(-)-leucine can be recommended as soluble lubricant for formulations containing aspartame and mannitol.     

Differential Scanning Calorimetry of Aspartame-Mannitol Mixture

Abstract

Differential scanning calorimetry was used to study both the qualitative and quantitative thermal properties of mixtures of aspartame with both mannitol and granular mannitol. Aspartame was found to be compatible with both forms of mannitol. No aspartame decomposition was observed in the preparation of a fused aspartame-mannitol mixture prepared at 161-165°C. L-(-)-leucine can be recommended as soluble lubricant for formulations containing aspartame and mannitol.     

Intercalation of n-alkylamines into α-tin(IV) bis(hydrogenphosphate)

The intercalation reaction of n-alkylamines from methyl- to hexadecylamine into -tin(IV) bis(hydrogenphosphate) has been investigated. The reaction was conducted by mixing the phosphate and solutions of the amines dissolved in water or benzene. The amine/ phosphate molar ratios in the reaction mixtures were 0.43, 0.85, 1.71 and 3.41. The nitrogen/phosphorus atomic ratio in the intercalation compound was not changed by the amine/phosphate molar ratio. The interlayer distances of the intercalates obtained in the reaction mixtures with molar ratios of 3.41 and 1.71 increased with an increase in the number of carbon atoms in the alkyl chain of the amine. The slope of the straight line obtained in plot of interlayer distance versus number of carbon atoms in the alkyl chain of the amine indicates that the amine molecules form a double layer in the interlayer space of the phosphate and are inclined at an approximate angle of 67.7° to the phosphate layer. The interlayer distances of the intercalates of butyl- to nonylamines obtained at the molar ratio of 0.85 are smaller than those of the corresponding compounds from the molar ratios of 3.41 and 1.71, while those of decyl- to hexadecylamine intercalates lie on the previously discussed line. This behaviour is interpreted by assuming kink formation in the short alkyl chains between the phosphate layers.     

Complexation between risperidone and amberlite resin by various methods of preparation and binding study

Purpose: The purpose of this work was to investigate the effect of preparation methods and the drug-to-resin ratio on complex formation between risperidone and amberlite resin. Methods: The existence of such resin complex may provide taste-masking properties to the dosage forms. It is important to determine when and how the complex forms. Therefore, in this study, the complexes of risperidone and amberlite resin were prepared by granulation, solution, and freeze-drying methods at various drug-to-resin ratios. The physical mixtures of drug–resin were used to compare the results of complexes prepared by granulation, solution, and freeze drying. The complexes were evaluated by various methods of characterization including differential scanning calorimetry, X-ray diffraction, spectroscopy (near infrared, Fourier transform infrared, and Raman), drug release, and binding studies. Results: Complexation between risperidone and amberlite was investigated for various preparation methods. It was found that complexation occurred at lower amounts of amberlite resin (drug-to-resin ratios of 1:1 and 1:2) when solution form of drug was contacted with the resin as in the case of solution and freeze-drying techniques compared with granulation (drug-to-resin ratios of 1:4 and 1:6). Characterization studies such as differential scanning calorimetry, X-ray diffraction, spectroscopic techniques, and drug release studies differentiated complexes from the physical mixtures. Binding studies between them revealed that the binding was linear with solubility of the drug limiting the adsorption capacity. Conclusions: Results of the study highlighted the importance of the preparation methodologies to formulate complexes. When the drug and the resin were simply mixed physically, no complexation occurred. Thus, a careful evaluation of manufacturing procedure would indicate the nature and extent of complexation.     

Enhancement of dissolution rate and bioavailability of sulfamethoxazole by complexation with β-cyclodextrin

The purpose of this study was to improve the solubility and dissolution rate of sulfamethoxazole (SMZ) with inclusion compound of β-cyclodextrin (β-CD). The interaction between SMZ and β-CD in solution was studied by the phase-solubility method. The phase-solubility studies revealed the formation of inclusion complexes with poor solubility with an inclusion complex of 1:1 molar ratio and a stability constant of 122.3?M(-1). The solid complexes of SMZ with β-CD were prepared by using kneading and coprecipitation methods. The physical mixture of these chemicals was also prepared for comparison. Inclusion complexation was confirmed by the results from the studies of infrared spectoroscopy (IR) and differential scanning calorimetry (DSC). The effect of water-soluble polymers i.e., polyethylene glycol 20000 and non-ionic surfactants i.e., polysorbate 20 on the complexation of SMZ with β-CD was also investigated by the same methods. The rates of release of the active material from the complexes were determined from dissolution studies using USP XXII paddle method. The formulation, that provided delivery of active material near to the target value in six healthy volunteers and in vivo tests, clearly revealed that the bioavailability of active material was found to be enhanced by preparing ternary mixtures.     

Synthesis of Ca–Mg Apatite via a Mechanochemical Hydrothermal Process

Mixtures of calcium and magnesium hydroxides and calcium dihydrogenphosphate in various molar ratios were ground in water with a fine grinding machine, which features multiring grinding media. Mechanochemical amorphization of the mixtures occurs quickly by grinding. The mixtures, after grinding for 5, 20, and 60 min, were then subjected to hydrothermal treatment at 573 K for 24 h. The influence of Mg/(Mg + Ca) molar ratio on the thermal behavior of the mechanically activated powders and the structure of the final products has been investigated. The microhomogeneity of Mg, Ca, and P elements on the samples is enhanced by the mechanochemical treatment. A shift in the X-ray diffraction peaks was observed among the final products with different grinding times, presumably due to a partial substitution of calcium by magnesium.     

Copper-iron bimetal modified PAN fiber complexes as novel heterogeneous Fenton catalysts for degradation of organic dye under visible light irradiation

A series of Cu-Fe bimetal amidoximated polyacrylonitrile (PAN) fiber complexes with different molar ratios of Cu(2+) to Fe(3+) ions was prepared using a simple exhaustion method, and characterized using FTIR, DRS and XPS, respectively. Then they were tested as the heterogeneous Fenton catalysts for Rhodamine B degradation with H(2)O(2) in the dark and under visible light irradiation. The results indicated that Cu-Fe bimetal amidoximated PAN fiber complexes could more effectively catalyze the dye degradation in water than Fe amidoximated PAN fiber complex, especially in the dark. And introduction of Cu(2+) ions significantly increased their catalytic performance. 0.56 was the optimum molar ratio of Cu(2+) to Fe(3+) ions to achieve the best catalytic activity and stability. This was mainly due to the synergetic effect in the bimetal complexes. Visible light irradiation improved the catalytic activity of the complexes, especially with a low molar ratio of Cu(2+) to Fe(3+) ions.     

Affinity capillary electrophoresis for the assessment of complex formation between viruses and monoclonal antibodies

The formation of complexes of human rhinovirus (serotype HRV2 and HRV14) with nonaggregating neutralizing monoclonal antibodies was investigated by affinity capillary electrophoresis. The method is based on preincubation of virus with antibody, followed by CE analysis. At low antibody-to-virus ratios, peaks corresponding to the complexes were broad, pointing to the presence of a heterogeneous population of virions with various numbers of antibodies bound; at a high molar ratio between virus and antibody, the peak became narrow again, indicating saturation of the 60 equivalent viral epitopes with the antibodies being attached bivalently. As SDS was used as an additive in the background electrolyte to allow for separation, its influence on complex formation was investigated. Once formed, HRV2-antibody complexes were found to be stable in the presence of the detergent but complex formation in buffer containing SDS was severely impaired. HRV14-antibody complexes were rapidly dissociated by SDS. The method proved to be useful for a rapid assessment of complex formation and might allow for an estimation of the binding stoichiometry.     

Multicomponent fluorometric analysis using a fiber-optic probe

Single-frequency phase-resolved fluorometry through single and bifurcated fiber-optic probes is used to quantify mixtures of spectrally similar fluorophores. Correlation coefficients from correlation plots are greater than 0.98, and standard errors of estimate are less than 0.13 microM for 80 binary mixtures. Quantification of fluorophores at up to 10:1 molar ratios with lifetime separations of less than 200 ps is possible. The simultaneous quantification of the individual components of ternary and quaternary synthetic mixtures is demonstrated. Application of phase resolution to ambient light rejection is reported also. In this case, the emission spectrum of 10 nM Rhodamine 6G is easily obtained in the presence of a fluctuating, unmodulated background.     

Aspartame optical biosensor with bienzyme-immobilized eggshell membrane and oxygen-sensitive optode membrane

An aspartame optical biosensor has been fabricated by employing a bienzyme system composed of alpha-chymotrypsin and alcohol oxidase immobilized onto an eggshell membrane and an oxygen-sensitive optode membrane as the transducer. The detection schemes involve the enzymatic reactions of aspartame leading to the depletion of the oxygen level of the medium with a concomitant enhancement of the fluorescence intensity of the oxygen-sensitive membrane. The scanning electron and transmission electron micrographs show the microstructure of the eggshell membrane which is successfully immobilized with bienzyme. Using this novel immobilization technique, the aspartame biosensor shows extremely good stability with a shelf life of at least 8 months. The rate change of the fluorescence intensity in 4 min is found to be linearly related to the concentration of aspartame. The useful analytical working range of the biosensor is from 0.056 to 3.07 mM aspartame. The effects of temperature, pH, and ionic strength on the response of the aspartame biosensor are investigated in detail. Citric acid, cyclamic acid, D-fructose, D-galactose, D-glucose, hydrogen peroxide, DL-malic acid, L-phenylalanine, saccharin, sodium benzoate, and sucrose show no interferences but ethanol interferes strongly. The aspartame biosensor has been applied to determine aspartame contents in some commercial products.     

Thermodynamic properties and excess volumes of 2,2,4-trimethylpentane + n-heptane mixtures from 298 to 338 K for pressures up to 400 MPa

(p, V, T) data for mixtures of 2,2,4-trimethylpentane (TMP) and heptane have been obtained in the form of volume ratios for four temperatures in the range 298.15 to 338.15 K for pressures up to 390 MPa. The data have been represented by the Tait equation of state for the purposes of interpolation and extrapolation. The atmospheric pressure densities of both pure components and their mixtures for three temperatures have been measured and used to determine the excess molar volumes. Isothermal compressibilities have been evaluated from the volumetric data.