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At least 19 recordsLinked to original sources
PubMed1999

Micro-thermal analysis: scanning thermal microscopy and localised thermal analysis.

Micro-thermal analysis combines the imaging capabilities of atomic force microscopy with the ability to characterise, with high spatial resolution, the thermal behaviour of materials. The conventional AFM tip is replaced by a miniature heater/thermometer which enables a surface to be visualised according to its response to the input of heat (in addition to measuring its topography). Areas of interest may then be selected and localised thermal analysis (modulated temperature calorimetry and thermomechanical analysis) carried out. Localised dynamic mechanical measurements are also possible. Spatially resolved chemical analysis can be performed using the same basic apparatus by means of pyrolysis gas chromatography-mass spectrometry or high-resolution photothermal infrared spectrometry.

Acetaminophen↗
PubMed2001

Characterization of soft gelatin capsules by thermal analysis.

Thermal analysis of soft gelatin capsule was used as a diagnostic tool to evaluate the effect of temperature and humidity stress conditions as well as formulation water, propylene glycol and ethanol on the softening of the gelatin shells. Results obtained using modulated and conventional DSC given as DeltaT(m) (change in gel-sol transition temperature) were compared with the results obtained using manual hardness tester given as % hardness loss. No difference between the two methods was observed in their ability to determine the extent of softening due to formulation water, propylene glycol and ethanol content. Thermal analysis and shifts in the reversible heat flow determined using MDSC provided additional insight into the structural changes and extent of deformation within the gelatin network upon exposure to formulation ingredients, temperature and humidity. Modulated thermal analysis is, therefore, a useful tool for screening the variables influencing the hardness of gelatin capsules.

Calorimetry, Differential Scanning↗
PubMed2002

Pharmaceutical applications of micro-thermal analysis.

Micro-thermal analysis is a recently introduced thermoanalytical technique that combines the principles of scanning probe microscopy with thermal analysis via replacement of the probe tip with a thermistor. This allows samples to be spatially scanned in terms of both topography and thermal conductivity, whereby placing the probe on a specific region of a sample and heating, it is possible to perform localized thermal analysis experiments on those regions. In this minireview, the principles of the technique are outlined and the current uses within the polymer sciences described. Current pharmaceutical applications are then discussed; these include the identification of components in compressed tablets, the characterization of drug-loaded polylactic acid microspheres, the analysis of tablet coats, and the identification of amorphous and crystalline regions in semicrystalline samples. The current strengths and weaknesses of the technique are outlined, along with a discussion of the future directions in which the approach may be taken.

Crystallization↗
PubMed1992

Thermal analysis of commercial Gutta-percha using differential scanning calorimeter and dynamic mechanical thermal analysis.

Gutta-percha is the most widespread root canal filling material and knowledge of its chemical and thermomechanical properties is of a great interest to its use in clinical dentistry. In the present investigation, the results from differential scanning calorimeter were compared with those obtained by dynamic mechanical thermal analysis. A significant correlation was established between these results and the chemical composition of six different commercial samples of gutta-percha.

Calorimetry, Differential Scanning↗
PubMed2001

The Modification of Hydroxyl Surfaces of Formamide-Intercalated Kaolinites Synthesized by Controlled Rate Thermal Analysis.

Controlled rate thermal analysis (CRTA) technology made possible the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites. X-ray diffraction shows that the CRTA-treated formamide-intercalated kaolinites remain expanded after CRTA treatment. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites with both intercalated and adsorbed formamide. An intense band is observed at 3629 cm(-1), attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm(-1) and are attributed to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl stretching band of the inner hydroxyl is readily observed at 3621 cm(-1) in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. The Raman bands of the formamide in the CRTA-treated intercalated kaolinites are readily observed. Copyright 2001 Academic Press.

Journal Article↗
PubMed1986

Applications of thermal analysis in the pharmaceutical industry.

Thermal analysis includes all methods measuring some parameter during the heating of a sample. Differential scanning calorimetry (or differential thermal analysis) where the parameter is heat flow into and out of the sample and thermogravimetry where the parameter is the weight change of the sample are of great value for the pharmaceutical industry. Characterisation of drug substance, excipients, and packaging material: identification, purity, polymorphism, solvation, stability, ..., may be routinely done. Further examples demonstrating the use of these methods for the development of the dosage form are given: choice of the salt form, phase-diagrams, drug substance-excipient interactions, physical changes on processing or during storage, and even analysis of the dosage form.

Journal Article↗
PubMed1996

[Application of thermal analysis to quality evaluation tests of drugs].

Thermal analysis method can be applied to the quality evaluation tests of drugs. Recent advances in the technology and the data-processing system on the apparatus have accelerated the utilization of this analytical techniques in the field of drug quality control. In this report, various application techniques of the thermal analysis such as DSC, DTA, TG and the impurity analysis by DSC, were reported and discussed from the viewpoints of a general test in the Japanese Pharmacopoeia. Further the present situations of this analytical method in the US Pharmacopoeia 23 and the British Pharmacopoeia 1993 are also explained.

Differential Thermal Analysis↗
PubMed1975

Thermal analysis of human stratum corneum.

A thermal analysis technique has been developed and used to detect the melting of lipids and denaturation of proteins in stratum corneum. Trasitions were observed at 40 degrees C, 75 degrees C, 85 degrees C, and 107 degrees C. The transitions at 40 degrees C were attributed to the melting of lipids. The transition at 85 degrees C was identified as due to the denaturation of alpha-keratin, and the transition at 107 degrees C to the denaturation of a nonfibrous protein. It was found that alteration of the conformation of the nonfibrous protein changed the state of water absorbed, and that water contributed to the ordering of the lipid and protein. The thermal analysis technique may prove to be of value in studying the interaction of materials with skin.

Body Water↗
PubMed1994

Subzero thermal analysis of human stratum corneum.

The thermal behaviour of human stratum corneum was studied using differential thermal analysis within the temperature range of -130 degrees C to 120 degrees C. Aside from thermal transitions at around 40 degrees C, 70 degrees C, 85 degrees C and 100 degrees C, which have been reported before, a particular transition below 0 degree C (subzero), at approx. -9 degrees C (264 K), was noticed. This transition was present in the analysis curves of dehydrated as well as hydrated stratum corneum sheets and could be distinguished from the water peak found only in hydrated stratum corneum samples. To further characterize this transition, thermal analysis was performed on stratum corneum sheets: (i) after lipid extraction, (ii) after pretreatment of propylene glycol and (iii) after pretreatment of oleic acid/propylene glycol solution. From the results, it was concluded that the subzero transition (-9 degrees C) belongs to low melting lipid components of stratum corneum.

Cold Temperature↗
PubMed2003

Determination of calcium oxalate (mono- and dihydrate) in mixtures with magnesium ammonium phosphate or uric acid: the use of simultaneous thermal analysis in urinary calculi.

BACKGROUND: The human urinary calculi are mainly formed from calcium oxalate, magnesium ammonium phosphate hexahydrate (MAPH) and uric acid (UA) crystals. It is important for the physician and surgeon to distinguish the two types of hydrates of calcium oxalate, mainly mono- (COM, Whewellite) and dihydrate (COD, Weddelite). This is because COM stones are evacuated two times more frequently than COD, which sometimes needs to be extracted surgically. METHODS: Thermal analysis techniques, such as Differential Thermal Analysis (DTA) and Thermogravimetry (TG), are considered the best techniques for the characterization of the two hydrates of calcium oxalate. A simultaneous thermal analysis method (TG-DTA) was applied to determine the percentage of each hydrate (COM and COD) when present together, in the presence of MAPH or in the presence of UA. RESULTS: The results performed on 156 urinary calculi were as follows (according to the major component): 74.36%, 7.05% and 10.26% for calcium oxalate hydrate, UA and MAPH, respectively. The COD/COM ratios were 0.75 and 1.75, when they are present in mixtures with UA and MAPH, respectively. CONCLUSIONS: Fourier transform infrared (FTIR) and X-ray diffraction (XRD) have been used in urinary calculi analysis. Simultaneous thermal analysis TG-DTA would be an alternative method for quantitative determination of the two types of calcium oxalate in urinary stones.

Calcium Oxalate↗
PubMed1970

Study of the thermal denaturation of ribonuclease A by differential thermal analysis and susceptibility to proteolysis.

1. The thermally induced change in conformation of ribonuclease A in solution was investigated by differential thermal analysis and the susceptibility of the enzyme to proteolytic digestion by ficin. 2. A transition with a mid-point of 60.5 degrees C at pH4.2 was observed directly by differential thermal analysis and shown to be a property of the native structure. 3. At pH4.2 ribonuclease A is susceptible to ficin digestion at 60 degrees C but not at 18 degrees C. 4. Chromatographic analysis of the digestion products reveals that transient active intermediates are produced during the digestion. 5. Three of these intermediates were purified and partially characterized. 6. The nature of those sections of the ribonuclease molecule that are involved in the thermal transition is discussed.

Amino Acids↗
PubMed2002

Emanation thermal analysis study of the preparation of ruthenia-titania-based finely dispersed powders.

Emanation thermal analysis (ETA), thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction analysis (XRD), and transmission electron microscopy (TEM) were used for the characterization of thermal behavior of hydrous oxides (RuO(2))(x)-(TiO(2))(1-x).nH(2)O and dehydrated oxides (RuO(2)) (x)-(TiO(2))(1-x), respectively (x=1, 0.9, and 0.7) on heating in argon and argon +10% hydrogen, respectively. The samples were heated in the range 20-600 degrees C at the constant heating rate 6 K/min. From the TG and DTA results the temperature intervals of dehydration and/or reduction of ruthenium dioxide into Ru metal were determined. ETA (based on the measurement of radon previously incorporated into the sample) brought about the information about surface area development and microstructure changes in the near surface layers up to 80 nm under in situ conditions of the heating. The temperature intervals of the annealing of near surface and structure defects serving as diffusion paths for radon were determined from the ETA results.

Argon↗
PubMedDate not supplied

Thermal analysis of whole soils and sediment.

Thermal analysis techniques were utilized to investigate the thermal properties of two soils and a lignite coal obtained from the International Humic Substances Society (IHSS), and sediment obtained from The Netherlands. Differential scanning calorimetry (DSC) revealed glass transition behavior of each sample at temperatures ranging from 52 degrees C for Pahokee peat (euic, hyperthermic Lithic Medisaprists), 55 degrees C for a Netherlands (B8) sediment, 64 degrees C for Elliott loam (fine, illitic, mesic Aquic Arguidolls), to 70 degrees C for Gascoyne leonardite. Temperature-modulated differential scanning calorimetry (TMDSC) revealed glass transition behavior at similar temperatures, and quantified constant-pressure specific heat capacity (Cp) at 0 degrees C from 0.6 J g(-1) degrees C(-1) for Elliott loam and 0.8 J g(-1) degrees C(-1) for the leonardite, to 1.0 J g(-1) degrees C(-1) for the peat and the sediment. Glass transition behavior showed no distinct correlation to elemental composition, although Gascoyne Leonardite and Pahokee peat each demonstrated glass transition behavior similar to that reported for humic acids derived from these materials. Thermomechanical analysis (TMA) revealed a large thermal expansion followed by a matrix collapse for each sample between 20 and 30 degrees C, suggesting the occurrence of transition behavior of unknown origin. Thermal transitions occurring at higher temperatures more representative of glass transition behavior were revealed for the sediment and the peat.

Calorimetry, Differential Scanning↗