A differential scanning calorimetric study of some phenol derivatives

Differential scanning calorimetry has been applied to derive the fusion enthalpies and entropies of series of mono and dimethylphenols, mono and dichlorophenols, and mono and dinitrophenols.

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Zusammenfassung DSC wurde verwendet zur Ermittlung der Schmelzenthalpie und Entropie der Reihen von Mono- und Dimethylphenolen, Mono- und Dichlorphenolen, Mono- und Dinitrophenolen.

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Development of a fitting model suitable for the isothermal titration calorimetric curve of DNA with cationic ligands

A novel curve fitting model was developed for the isothermal titration calorimetry (ITC) of a cationic ligand binding to DNA. The ligand binding often generates a DNA conformational change from an elongated random coil into a compact collapsed form that is referred to as "DNA condensation". The ligand binding can be classified into two regimes having different binding constants Ki, i.e., the binding to an elongated DNA chain with a binding constant K1 and with K2 that occurred during the conformational transition. The two-variable curve fitting models are usually bound by a strict regulation on the difference in the values of the binding constants K1 > K2. For the DNA condensation, however, the relationships for K1 and K2 are still unclear. The novel curve fitting model developed in this study takes into account this uncertainty on the relationship of the binding constants and is highly flexible for the two-variable binding constant system.     

Analytical comparison of calorimetric,enzymatic and chemical methods for the quantitative determination of cholic acids

Several methods for the determination of cholic acids have been examined using pure cholic acid as standard. Some analytical aspects have been checked and evaluated. Two methods based on DSC were considered using the detection and measurement of the heats of oxidation and heats of fusion, respectively. The results were compared with those obtained both by the enzymatic method using 3α-hydroxysteroid dehydrogenase as reagent and by a chemical method based on the Pettenkofer reaction. Operative procedures of the last method have been tested and improved with respect to the Irvin procedure in some cases.The discussion is reported in terms of precision, sensitivity and possible fields of application for the examined method.     

The calorimetric study of some guanidine derivatives involved in living bodies nitrogen metabolism

The energies of combustion of creatine (anhydrous and monohydrate), creatinine, and arginine were measured in a static bomb adiabatic calorimeter, in pure oxygen at 3,040 kPa. The derived standard enthalpies of formation in solid state of the above-mentioned compounds are, respectively, −520.4 ± 4.3, −809.7 ± 1.3, −204.2 ± 7.0, and −634.8 ± 2.3 kJ mol⁻¹ . The data of enthalpy of formation are compared with literature values and with estimated values by means of group additivity. The dehydration of creatine monohydrate and the processes occurring in the three guanidine derivatives at temperatures exceeding 200 °C were investigated by means of DSC.     

Some problems in adsorption and calorimetric studies of the steps of catalytic processes

Principal side factors as well as technical and procedural peculiarities capable of distorting the results of measurements of adsorbed and desorbed amounts, of falsifying the nature of the processes proceeding in the systems under study, and of promoting artifacts in calorimetric and other studies of gas chemisorption on powders are considered. Modified techniques and procedures allowing the elimination of sources of side phenomena and artifacts and freeing traditional glass static adsorption apparatuses and experimental procedures from undesirable factors and peculiarities are proposed. Some available chemisorption and calorimetric data representing artifacts and also some data that are not artifacts but,due to imperfections of chemisorption techniques, show up as artifacts are presented and discussed. Several applications of the improved techniques and procedures to calorimetric and adsorption studies of the steps of catalytic processes proceeding on the basis of natural gas and of products of its processing are presented and discussed.     

Phase behavior and some calorimetric and physical properties of diurethanes from perfluoropolyether macromonomers

Density and calorimetric measurements have been carried out on copolymeric perfluoropolyethers of molecular weight ranging between 500 and 4700, terminated at both chain ends either with  CH₂OH or ethylurethane groups. Samples of the second series are models for perfluoropolyethers based polyurethanes. Density measurements point out that the terminal alcoholic group brings about a negative excess volume, which increases with decreasing the molecular weight; a lower excess volume is found for urethane‐terminated molecules. Calorimetric traces, T_g, and Δc_p at T_g show that alcoholic‐terminated molecules are amorphous and one phase systems, while urethane‐terminated compounds are crystalline; phase separation is observed for this last series when the molecular weight of the fluorinated segment is larger than 1000. The trend of T_g with molecular weight is discussed for one‐ and two‐phase systems in the light of current theories for the glass transition. The decrease of the melting point with increasing the molecular weight for the urethane series can be described by the Flory equation for random copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1609–1622, 1999     

A calorimetric study of the silver (I) complexes of some sulfur-containing amines

The enthalpies of the reactions in 0.5 M KNO₃ at 25°C between the hydrogen and silver(I) ions and a number of sulfur-containing amines of the general formula R'-S-(CH₂)NR₂ where

and n=2,3, have been determined by means of direct calorimetric titrations. By the use of the ΔG values reported elsewhere, the corresponding ΔS values have been calculated. the complex formation in acid, neutral and alkaline medium is discussed.     

Characterization and quantification of amorphous content in some selected parenteral cephalosporins by calorimetric method

Summary Amorphous content of a crystalline drug affects its physical and chemical properties as well as its performance. Consequently it is important to assess the extent of amorphous contents in pharmaceuticals. The present study utilizes the technique of solution calorimetry to quantify the percentage of crystallinity in samples of varying amorphous content in cefazolin sodium monohydrate, ceftriaxone sodium, cefotaxime sodium and cefoperazone sodium. Enthalpy of solution of 100% crystalline and amorphous drugs as well as their physical mixtures over the range 0-100 mass/mass% amorphous content were determined. As expected it has been found that amorphous forms have significantly higher energy than the corresponding crystalline form for all the drugs. Enthalpy of solution (Δ_solH), an extensive thermodynamic property can provide a precise and unambiguous measure of the relative crystallinity provided amorphous and crystalline standards are appropriately chosen. A good correlation has been found between Δ_solH and the amorphous contents of the drugs.     

Impurity-profiling UPLC methods for quantitative analysis of some antiemetics formulated with pyridoxine

Cyclizine hydrochloride (CYC) and meclozine hydrochloride (MEC) are antihistaminic drugs generally co-formulated with pyridoxine hydrochloride (PYR) to treat nausea and vomiting in pregnancy. Several analytical techniques have been applied for the determination of CYC or MEC with PYR, but determination of CYC impurity; benzhydrol (BEH) or MEC impurity; or 4-chlorobenzophenone (BEP) has not been paid attention to. Therefore, micellar UPLC method is introduced for analysis of ternary mixtures containing PYR together with both CYC and BEH (mixture I) or MEC and BEP (mixture II). Chromatographic separation was achieved using a Hypersil gold C₈ column (50 × 2.1 mm, 1.9 μm) using 0.01 M sodium dodecyl sulfate modified to pH 3.5 using phosphoric acid:acetonitrile (45:55 by volume) for mixture I and 0.1% sodium dodecyl sulfate, 0.1% sodium bicarbonate adjusted to pH 2.6 by phosphoric acid:acetonitrile (47:53 by volume) for mixture II as mobile phases. The separated peaks were detected at 230 and 245 nm for mixtures I and II, respectively. The adopted methods were validated in conformance with the International Conference on Harmonization (ICH) recommendations and were properly applied in commercial pharmaceutical formulation analysis. Comprehensive ecological comparison was achieved, confirming a higher ecological value of the presented methods compared to the earlier reported methods.     

Studies on some materials suitable for use as internal standards in high energy EPR dosimetry

EPR-spectroscopic properties (line-intensity,-width, andg-factors) of pyrolized at 550°C sucrose, MgO and MgO doped with Mn²⁺ ions (500∶1) remain unchanged after high-dose (1–100 kGy) irradiation, whereas CaO gives an EPR signal. These properties of these materials make it possible to use them as internal reference EPR standards in the work under conditions of strong ionisation environment, for precise determination of theG-values of other materials, for obtaining exact magnitudes of increase of the EPR response when the method of additional dose is applied, to follow the kinetics of decay of some radiation induced defects.     

Review of DBS methods as a quantitative tool for anticancer drugs

An overview of published dried blood spot (DBS) methods for the quantitation of various classes of anticancer drugs from clinical and preclinical studies is presented. The increased reporting of DBS methods in the literature for quantitation of various classes of drugs is a testimony to their utility in bioanalytical applications. While DBS offers several advantages as compared with conventional wet sampling techniques, there remain a number of nuances that may impede the assay adaptability of DBS method in routine quantitative bioanalysis. This review covers several case studies of DBS application in the quantitation of anticancer drugs. Some perspectives are provided on the optimization of the DBS method with respect to the selection of DBS card, spot volume, hematocrit effect and other regular validation parameters, which are essential in quantitative bioanalysis. Some thoughts are provided on the existing gaps in the DBS method and possible remedial measure(s) to address such gaps. Although DBS methods have great potential, there is the need for a global consensus including regulatory support on the type of validation experiments to be performed to support quantitative data.     

Development of a calorimetric sensor for medical application

A calorimetric sensor has been developed to measure the calorific dissipation through a determined area of the human body surface. An experimental laboratory prototype with a capturing surface of 36 cm² has been built, and a functioning model suggesting an operational method that allows to determine the calorific power going through the sensor has been proposed.     

Applications of Haar basis method for solving some ill-posed inverse problems

In this paper a numerical method consists of combining Haar basis method and Tikhonov regularization method for solving some ill-posed inverse problems using noisy data is presented. By using a sensor located at a point inside the body and measuring the u(x, t) at a point x?=?a, 0?<?a?<?1, and applying Haar basis method to the inverse problem, we determine a stable numerical solution to this problem. Results show that an excellent estimation on the unknown functions of the inverse problem can be obtained within a couple of minutes CPU time at pentium IV-2.4?GHz PC.     

Model of a calorimetric sensor for medical application

A calorimetric sensor has been developed to measure surface heat dissipations in the human body. An experimental prototype has been built in order to study its performance and a simple model that represents acceptably the experimental system has been proposed.     

Development of a calorimetric sensor for medical application

A calorimetric sensor has been developed for local and direct measurement of calorific dissipations in different parts of the human body. The constructed prototype has a detection surface of 36 cm². The calibration of the sensor is based on a semi-empirical model that permits to simulate the operation of the device, making easier an operational functioning method. The device is modeled as a system with two inputs and two outputs. The inputs are the calorific power (W) that is intended to be measured and the power (W _pid) that dissipates a resistance, keeping constant the thermostat temperature through the use of a PID controller. The outputs are the thermostat temperature (T _pid) and the calorimetric signal (y) that provides the thermopile that is in contact with the body.     

Development of a calorimetric sensor for medical application

A calorimetric sensor has been developed for local and direct measurement of calorific dissipations in different parts of the human body. The constructed prototype has a detection surface of 36 cm². In this paper, a deconvolution method is proposed to reconstruct the dissipated power. The advantage of this method is that: to determine the dissipated power, it is not necessary to correct the baselines to calculate either the areas of the calorimetric signal or that of the dissipated power in the temperature control because the proposed method takes into account, apart from the calorimetric signal, the thermostat temperature and the ambient temperature.     

Formulation design of ointment base suitable for healing of lesions in treatment of bedsores

We intended to develop a desired ointment base suitable for treatment of bedsores including the proliferation of granulation and epidermis. The main bedsore bacteria detected in our hospital were S. aureus in gram-positive coccus and P. aeruginosa in gram-negative bacillus. As the macrogol ointment (MO) was found to have bactericidal effects on these bacteria, MO was adopted as the base for the objective ointment. To improve the properties of the ointment base such as regulating the humidity of the exudation and controlling the release of antibiotics formulated in the ointment, co-formulating effects of various additives to MO were evaluated. The sustained release function of the ointment base was obtained by adding hydrophilic petrolatum (HP) to MO. However, the resultant ointment was found to have a poor humidity regulating property. On the other hand, MO containing 5% of hydroxypropyl cellulose (HPC) showed both the humidity regulating and the controlled drug releasing properties. It was considered that HPC particles dispersed in the ointment could be swelled by absorbing water to form a gel network. The curd tension meter tests for the ointments prepared with the various polymers showed that the MO-HPC base, which showed the highest sustained drug releasing property, was found to have the highest hardness. This result means that HPC formulated into the base forms the most rigid gel structure to resist the erosion of the ointment and to control the drug release.     

Comparative studies on some methods for handling quantitative data generated by analytical pyrolysis

A number of multivariable statistical techniques have been prepared for handling programs or mass spectra. The more widely used methods are reviewed and their application, the microbiological data set compared. The results are drawn together to formulate a XXXXX data handling rationale capable of processing a variety of pyrolyses applications.