[Application of thermal analysis to the determination of the purity of chemical drugs. Chlorprothixene as an example].
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Chemistry Techniques, Analytical↗
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Thermal analysis as a screening technique in preformulation studies of picotamide solid dosage forms.
The potential compatibilities of several commonly used pharmaceutical excipients with picotamide were evaluated using differential scanning calorimetry (DSC). The effects of aging and of mechanical treatment (blending, grinding, or kneading) of samples were also evaluated. Hot-stage microscopy (HSM) and scanning electron microscopy (SEM) were used as complementary techniques to implement and assist in interpretation of the DSC results. DSC analysis evidenced a noticeable modification of drug thermal features in the mixtures with palmitic acid, stearic acid, stearyl alcohol, polyethylene glycol (PEG) 20,000, and sorbitol, but HSM analysis showed that the DSC behavior was mainly because of the drug dissolution in the melted excipient, which allowed the presence of important solid-solid interactions to be excluded. Compatibility with Mg stearate was also found, even if sample manipulation induced the partial conversion of Mg stearate in a pseudo-polymorphic modification. Mechanical stress displayed an increased hygroscopicity of mixtures with glucose and lactose, as well as some solid-solid interactions with lactose and mannitol.
Calorimetry, Differential Scanning↗
[Differential thermal analysis and X-ray diffraction patterns of some poorly soluble drugs fixed onto silicon dioxide (author's transl)].
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Chemistry, Pharmaceutical↗
Application of XRF, XRD, thermal analysis, and voltammetric techniques to the study of ancient ceramics.
An in-depth chemical-analytical study has been performed on biscuit and mortar from 17th-18th century tiles from a mediaeval hermitage in the province of Valencia (Spain). Representative samples were chosen from the tile fragments available, using appearance, essentially color and consistency, as the criterion. The chemical composition was analyzed by X-ray fluorescence of the samples in the form of glass disks after a previous qualitative study to choose the standard materials for calibration and the experimental conditions used in the analysis. X-ray diffraction of the samples provided information about the mineralogical composition which was consistent with the firing of the original materials; it also gave information about the range of temperatures used in the firing. From thermal gravimetric analysis of the limestone, and from historical considerations, it was possible to deduce the raw materials used and their approximate composition in the tiles. In the same way it was possible to determine the nature of the mortars used to fix the tiles. Cyclic voltammetric study of the iron(II) and iron(III) system in the biscuit showed the simultaneous presence of both oxidation states, corroborating the results.
Journal Article↗
The use of differential thermal analysis and thermogravimetry to study the free and bound water of edema induced in rat skin by the toxin of Clostridium oedematiens.
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Animals↗
Studies on rapidly frozen suspensions of yeast cells by differential thermal analysis and conductometry.
Few, if any, yeast cells survived rapid cooling to -196 degrees C and subsequent slow warming. After rapid freezing, the suspensions absorbed latent heat of fusion between -15 degrees and 0 degrees C during warming, and the relation between the amount of heat absorbed and the concentration of cells was the same as that in equivalent KCl solutions, indicating that frozen suspensions behave thermally like frozen solutions. The amount of heat absorbed was such that more than 80 per cent of the intracellular solution had to be frozen. The conductometric behavior of frozen suspensions showed that cell solutes were still inside the cells and surrounded by an intact cell membrane at the time heat was being absorbed. Two models are consistent with these findings. The first assumes that intracellular freezing has taken place; the second that all freezable water has left the cells and frozen externally. The latter model is ruled out because rapidly cooled cells do not shrink by an amount equal to the volume of water that would have to be withdrawn to prevent internal freezing.
Cell Count↗
[The thermal analysis of mineral-based biomaterials used in dentistry. 5].
In this study the following commercial products were thermo-analysed (TG, DTG, DTA): reabsorbable Dac Blu, non reabsorbable Dac Blu, non reabsorbable atomized Dac Blu, non reabsorbable thin Dac Blu, reabsorbable Biocoral 450, non reabsorbable thin Dac Blu, reabsorbable Biocoral 450, Calcitite 2040-12, Orthogel, Apagen, BTF 65, Calcitite 4060-2, Osprogel, Bio-Oss, Biostite, Osprovit, Merck Hydroxiapatite. The apparatus utilized was a Setaram TAG 24, in a symmetrical set up, which gave the TG, DTG and DTA analysis simultaneously. The analysis of all the materials were performed in correct operative conditions. The thermo analyses gave useful information about the thermal stability of the samples. The TG analysis gave the data relative to the percentage of weight loss due to the volatile substances in the samples (H2Oass C, OH-, CO2). The DTG graph made it possible to establish the presence of carbonate apatite and/or hydroxyapatite or the absence of both the substances. Finally, DTA and DTG analyses allowed show the presence of various organic substances. These data were very useful to characterize the examined materials and confirmed the extreme importance and sensibility of this method.
Biocompatible Materials↗
An accurate and reliable method of thermal data analysis in thermal imaging of the anterior knee for use in cryotherapy research.
OBJECTIVE: To develop an anatomic marker system (AMS) as an accurate, reliable method of thermal imaging data analysis, for use in cryotherapy research. DESIGN: Investigation of the accuracy of new thermal imaging technique. SETTING: Hospital orthopedic outpatient department in England. PARTICIPANTS: Consecutive sample of 9 patients referred to anterior knee pain clinic. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Thermally inert markers were placed at specific anatomic locations, defining an area over the anterior knee of patients with anterior knee pain. A baseline thermal image was taken. Patients underwent a 3-minute thermal washout of the affected knee. Thermal images were collected at a rate of 1 image per minute for a 20-minute re-warming period. A Matlab (version 7.0) program was written to digitize the marker positions and subsequently calculate the mean of the area over the anterior knee. Virtual markers were then defined as 15% distal from the proximal marker, 30% proximal from the distal markers, 15% lateral from the medial marker, and 15% medial from the lateral marker. The virtual markers formed an ellipse, which defined an area representative of the patella shape. Within the ellipse, the mean value of the full pixels determined the mean temperature of this region. Ten raters were recruited to use the program and interrater reliability was investigated. RESULTS: The intraclass correlation coefficient produced coefficients within acceptable bounds, ranging from .82 to .97, indicating adequate interrater reliability. CONCLUSIONS: The AMS provides an accurate, reliable method for thermal imaging data analysis and is a reliable tool with which to advance cryotherapy research.
Analysis of Variance↗
[Thermal analysis of biological materials. II. Study of relations between composition and structure of hard dental tissues and their thermal properties].
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Dental Enamel↗
[Computer-aided differential thermal analysis of drugs].
An open-loop on-line computer connection to a DTA apparatus of high time constant and the developed software for data acquisition and utilization are described. The new system was calibrated thermomentrically and calorically. The main aim is a enhanced purity estimation, especially by using of the modified Van't Hoff equation based on DTA curves, which first must be transformed to process-power-curves. Computer aided DTA provides utilization of higher quality and makes them faster and more exactly. Plotting of DTA curves which are baseline corrected and constructed as mean of equal curves as well as zooming are powerful and essential tools in optical comparison. The better estimation of the baseline under the peak and the computation of process-power-curve from DTA curve enable estimations based on curves of DTA apparatus' with high time constant as like as bases on DSC-curves.
Computers↗
Thermal analysis study of the interactions between acetaminophen and excipients in solid dosage forms and in some binary mixtures.
Thermogravimetry (TG) and differential scanning calorimetry (DSC) were used to assess the compatibility between acetaminophen (Ac) and some excipients (polyvinylpyrrolidone (P), magnesium stearate (M), citric acid (C), aspartame (As), mannitol (Mn), cellulose (Cll) and starch (S)) in several of the more commercially available pharmaceutical formulations and in solid binary mixtures. The present study compared thermodynamic data on acetaminophen melting and vaporization processes of pure acetaminophen with those found for several solid mixtures and in some commercially available acetaminophen-based dosage forms. Appreciable modifications occur only for solid mixtures with high content of excipient. Acetaminophen-based dosage forms and its solid binary mixtures usually show "additivity" of calorimetric peaks number of pure components in their calorimetric curve profiles, thus revealing a good thermoanalytical compatibility between acetaminophen and the excipients examined, except for samples containing appreciable content of mannitol.
Acetaminophen↗
Diclofenac salts. I. Fractal and thermal analysis of sodium and potassium diclofenac salts.
Sodium and potassium diclofenac salts form hydrates when crystallized from water; the sodium salt contains four crystallization water molecules, while the potassium salt precipitates as a dihydrate. Crystallization from organic solvents occurs with a change of the crystal habit. The fractal dimension of the particle surface of both salts obtained from water is low and is in agreement with the formation of smooth and regular surfaces during crystallization. The fractal dimension for dissolution is relatively high and comparable for hydrate and anhydrate forms of both salts, and the result was interpreted as being due to the surfactant behavior of diclofenac anions. Thermograms of both salts show a couple of endotherms in the range 30-100 degrees C, which disappear when the salts have been previously heated at 100 degrees C, but slowly reappear when the anhydrate forms are stored in a humid environment. Both salts present a complex exotherm of decomposition at 284 and 314 degrees C, respectively. The results are briefly discussed with regard to the formulations of the anti-inflammatory agent diclofenac.
Anti-Inflammatory Agents, Non-Steroidal↗
Synthesis, characterization and thermal analysis of some new transition metal complexes of a polydentate Schiff base.
A new polydentate Schiff base (H3L) was synthesized from the condensation of 2,6-diformyl-4-methylphenol and S-methylhydrazine-carbodithionate. The 1:1 metal complexes were obtained from the interaction of H3L and the metal ions Cr(III), Co(II), Ni(II), Cu(II), Cd(II) and Hg(II). The complexes were characterized by elemental analysis and IR spectroscopy. Detailed studies of the thermal properties of the complexes were investigated by thermogravimetry techniques.
Hot Temperature↗
Finite element thermal analysis of bone cement for joint replacements.
A finite element technique was developed to investigate the thermal behavior of bone cement in joint replacement procedures. Thermal tests were designed and performed to provide the parameters in a kinetic model of bone cement exothermic polymerization. The kinetic model was then coupled with an energy balance equation using a finite element formulation to predict the temperature history and polymerization development in the bone-cement-prosthesis system. Based on the temperature history, the possibility of the thermal bone necrosis was then evaluated. As a demonstration, the effect of cement mantle thickness on the thermal behavior of the system was investigated. The temperature profiles in the bone-cement-prosthesis system have shown that the thicker the cement, the higher the peak temperature in the bone. In the 7 mm thick cement case, a peak temperature of over 55 degrees C was predicted. These high temperatures occurred in a small region near the bone/cement interface. No damage was predicted in the 3 mm and 5 mm cement mantle thickness cases. Although thermal damage was predicted in the bone for the 7 mm mantle thickness case, the amount of thermal necrosis predicted was minimal. If more cement is used in the surgical procedure, more heat will be generated and the potential for thermal bone damage may rise. The systems should be carefully selected to reduce thermal tissue damage when more cement is used. The methodology developed in this paper provides a numerical tool for the quantitative simulation of the thermal behavior of bone-cement-prosthesis designs.
Animals↗
Thermal analysis of cryoprotective solutions for red blood cells.
A differential scanning calorimeter was used to study the thermal behavior of glycerol-water solutions (binary system) and the more complex glycerol-based cryoprotective solutions that are used clinically in order to examine the cryoprotective role of glycerol in preserving frozen red blood cells. The melting and glass transition temperatures for the clinically used cryoprotective solutions were as expected, based on the nonequilibriumphase diagram for cryoprotective solutions incorporating isotonic phosphate-buffered saline. Two zones were identified in which solidification occurred without the formation of ice crystals: a glassy state that is crystallographically amorphous was found for glycerol concentrations between 40 and 55% in the binary system and between 45 and 60% in the complex system; a glassy state in the complete absence of ice was found at glycerol concentrations greater than 55% for the binary system or 60% for the complex system. In clinical practice, cryoprotectants are used at initial concentrations lower than those at which these two glassy states occur but there is an increase in the effective glycerol concentration inside and outside the cells as ice forms during the freezing process.
Blood Preservation↗
FDTD electromagnetic and thermal analysis of interstitial hyperthermic applicators. Finite-difference time-domain.
In this paper, the electromagnetic and thermal behavior of interstitial applicators was analyzed by using the Finite-Difference Time-Domain method. Two configurations were considered: a simple insulated dipole antenna radiating in a layered tissue, and an air cooled applicator radiating in a tissue-equivalent phantom. The proposed approach allows a detailed modeling of the complete structure of the applicator. Furthermore, Specific Absorption Rate and temperature distributions can be determined considering real clinical or experimental conditions. The temperature distribution for the air cooled applicator has been compared with experimental results.
Electromagnetic Phenomena↗
Thermal stability of disodium and calcium phosphomycin and the effects of the excipients evaluated by thermal analysis.
In the present study, Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) are simultaneously applied to determine the thermal properties of two antibiotic salts, disodium and calcium phosphomycin, used either pure or in association with several excipients. This study was carried out kinetically as well by mathematical elaboration of the TG curves performed according to an isothermal procedure applied at different fixed temperatures. Kinetic parameters showing agreement with those produced by the isothermal method were also obtained by means of a non-isothermal method using a dynamic TG curve alone. The main aims of the work were to provide reliable kinetic parameters (kinetic constant k, activation energy E(a) and pre-exponential factor A) to evaluate the thermal stability of phosphomycin salts in the presence and absence of the excipients generally contained in the phosphomycin-based pharmaceutical forms available on the market, and to obtain information concerning compatibility towards the active components. These kinetic parameters were then used to extrapolate shelf-life and half-life values at room temperature for pure active components in the solid state and for their pharmaceutical derivatives.
Anti-Bacterial Agents↗
Studies of interaction phenomena in aqueous-based film coatings containing soluble additives using thermal analysis techniques.
Interaction phenomena, in aqueous-based hydroxypropyl methylcellulose (HPMC) and polyvinyl alcohol (PVA) film-coating formulations containing water-soluble additives (citric acid and urea) have been examined by thermal methods to assess glass transition, softening, melting, plasticization, and crystallinity. The methods used were differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) in penetration and expansion modes. In addition to the established thermal transitions occurring in HPMC and PVA at relatively high temperatures, transitions were also observed between 26 and 43 degrees C using TMA. These low temperature transitions, unlike those occurring at the higher temperatures, were low energy transitions and not influenced by the type and concentration of the additives incorporated. The results also showed that the plasticizing activities of citric acid and urea were as high as those of some currently used plasticizers. On a weight basis, urea was superior to citric acid as a plasticizer for either HPMC or PVA, but when their molar contents were considered, the position was reversed. Also, PVA crystallinity was depressed in the presence of the additives.
Calorimetry, Differential Scanning↗