Differential scanning micro calorimetry

The interpretation of such data is usually based around fitting a series of models and deciding which offers the best fit. Data are normally obtained under dilute non-aggregating conditions. For instance, a simple two-stage denaturation model can be fitted by the following 

In the above equations A Gunfoid is the free energy of unfolding, A fanfold is the enthalpy of unfolding, Ko is the equilibrium constant for the unfolding reaction, Ctot is the total concentration of protein and TJn is the temperature of the transition, normally measured at the peak where A Gunfoid is zero. By use of the equation, AG = AH—TAS, so the reaction 

This simple model can be extended to include the effects of ligand binding firstly to the native structure, which stabilises the native state and so increases the temperature of transition. An equation describing this is 

The effective unfolding equilibrium constant is given by the ratio of the total concentration of unfolded to folded species. 

As mentioned previously, in addition to the directly determined calorimetric enthalpy, it is possible to define another enthalpy based upon the shape of the peak. Using the equation 

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Ghirlando, R., J. Lund, M. Goodall, and R. Jefferis. 1999. Glycosylation of human IgG-Fc influences on structure revealed by differential scanning micro-calorimetry. Immunol Lett 68 47-52. 

Abbreviations DSC, differentiai scanning caiorimetry DMA, dynamic mechanical analysis TGA, thermogravimetric analysis DTGA, differential thermogravimetric analysis RVA, rapid viscoanalyser DVS, dynamic vapour sorption ITC, isothermal titration calorimetry DSM/NC, differential scanning micro/nano-calorimetry. 

The worst hazard scenarios (excessive temperature and pressure rise accompanied by emission of toxic substances) must be worked out based upon calorimetric measurements (e.g. means to reduce hazards by using the inherent safety concept or Differential Scanning Calorimetry, DSC) and protection measures must be considered. If handling hazardous materials is considered too risky, procedures for generation of the hazardous reactants in situ in the reactor might be developed. Micro-reactor technology could also be an option. Completeness of the data on flammability, explosivity, (auto)ignition, static electricity, safe levels of exposure, environmental protection, transportation, etc. must be checked. Incompatibility of materials to be treated in a plant must be determined. 

Two papers reported powder pattern crystallographic results. The paper by Santos et al. (7) stood out from the rest because it presented a collection of more classical physical chemistry experiments. In this paper the authors described the use of micro-combustion calorimetry, Knudsen effusion to determine enthalpy of sublimation, differential scanning calorimetry, X-ray diffraction, and computed entropies. While this paper may provide some justification for including bomb calorimetry and Knudsen cell experiments in student laboratories, the use of differential scanning calorimetry and x-ray diffraction also are alternatives that would make for a crowded curriculum. Thus, how can we choose content for the first physical chemistiy course that shows the currency of the discipline while maintaining the goal to teach the fundamentals and standard techniques as well ... 

In order to optimize each embedding material property, complete cure of the material is essential. Various analytical methods are used to determine the complete cure of each material. Differential scanning calorimetry, Fourier transform-infrared (ftir), and micro dielectrometry provide quantitative curing processing of each material. Their methods are described below. 

In the CSM laboratory, Rueff et al. (1988) used a Perkin-Elmer differential scanning calorimeter (DSC-2), with sample containers modified for high pressure, to obtain methane hydrate heat capacity (245-259 K) and heat of dissociation (285 K), which were accurate to within 20%. Rueff (1985) was able to analyze his data to account for the portion of the sample that was ice, in an extension of work done earlier (Rueff and Sloan, 1985) to measure the thermal properties of hydrates in sediments. At Rice University, Lievois (1987) developed a twin-cell heat flux calorimeter and made AH measurements at 278.15 and 283.15 K to within 2.6%. More recently, at CSM a method was developed using the Setaram high pressure (heat-flux) micro-DSC VII (Gupta, 2007) to determine the heat capacity and heats of dissociation of methane hydrate at 277-283 K and at pressures of 5-20 MPa to within 2%. See Section 6.3.2 for gas hydrate heat capacity and heats of dissociation data. Figure 6.6 shows a schematic of the heat flux DSC system. In heat flux DSC, the heat flow necessary to achieve a zero temperature difference between the reference and sample cells is measured through the thermocouples linked to each of the cells. For more details on the principles of calorimetry the reader is referred to Hohne et al. (2003) and Brown (1998). 

For the determination of reaction parameters, as well as for the assessment of thermal safety, several thermokinetic methods have been developed such as differential scanning calorimetry (DSC), differential thermal analysis (DTA), accelerating rate calorimetry (ARC) and reaction calorimetry. Here, the discussion will be restricted to reaction calorimeters which resemble the later production-scale reactors of the corresponding industrial processes (batch or semi-batch reactors). We shall not discuss thermal analysis devices such as DSC or other micro-calorimetric devices which differ significantly from the production-scale reactor. 

Differential Scanning Calorimetry (DSC) was used for a long time in the field of process safety [21-23], This is essentially due to its versatility for screening purposes. The small amount of sample required (micro-calorimetric technique) and the fact that quantitative data are obtained, confer on this technique a number of advantages. The sample is contained in a crucible placed into a temperature controlled oven. Since it is a differential method, a second crucible is used as a reference. This may be empty or contain an inert substance. 

Fig. 4. Profile of a differential scanning calorimetry experiment done on a synthetic lysozyme. The heat capacity (kilocalories per degree per mole) of the unfolding process was monitored as a function of temperature on a Micro-Cal MC2 instrument. The transition midpoint of protein unfolding corresponds to the temperature at the peak of the curve, and the thermodynamic parameters A H and A Cp are evaluated by the procedure of Privalov.33...

Song, M., Liebenberg, W. and de Villers, M.M. (2006) Comparison of high sensitivity micro differential scanning calorimetry with X-ray powder diffractometry and FTIR spectroscopy for the characterization of pharmaceutically relevant non-crystalline materials. Die Pharmazie, 61... 

X-Ray Diffraction, Thermal Analysis (Differential Scanning Calorimetry, DSC, Thermogravimetric Analysis, TGA), and Micro-Eourier Transform Infrared Spectroscopy. 

PLCL (50 50) copolymers were basically random and amorphous. However, two values of were observed by differential mechanical analysis (DMA) and maybe also by differential scanning calorimetry (DSC) thermograms (Fig. 3.6 Jeong, 2004a). Furthermore, micro domains (about 17 nm size) were indicated on SAXS profile and finally confirmed by transmission electron microscopy (TEM) (Fig. 3.7). Therefore, the PLCL copolymer was probably composed of a soft matrix of mainly caprolactone moieties and... 

Low resolution mass spectra (LRMS) and high resolution mass spectra (HRMS) were recorded on an Associated Electronic Industries (AEI) Model MS-30 spectrometer. Intrinsic viscosities were measured by standard procedures using a Cannon-Ubbelohde semi-micro viscometer (dilution viscometer). Differential scanning calorimetry data for polymers were taken on a Perkin-Elmer DSC IB all data on thermal transitions are reported in degrees centigrade and are uncorrected. 

Liauw and co-workers have studied the adsorption of stearic acid onto magnesium hydroxide, using a variety of techniques, including DRIFTS and flow micro-calorimetry [8, 21]. The mono-layer level was again found to correspond well with a close packed vertical mono-layer. Evidence for order in the adsorbed layer was obtained by a number of techniques, including X-ray and differential scanning calorimetry. 

Poly(NIPAM-co-vinyl laurate) (poly(NIPAM-co-VL)) co-polymers were prepared at various feed ratios via conventional radical random co-polymerisation. The formation, composition ratios and molecular weight of co-polymers were examined. The thermoresponsive behaviour of poly(NIPAM) and poly(NIPAM-co-VL) solutions at low and high concentrations were intensively investigated by turbidity measurement, micro-differential scanning calorimetry (Micro-DSC), temperature-variable state fluorescence, IH NMR and DLS [62]. 

Thermal analysis (TA) comprises a family of measuring techniques that share a common feature they measure a material s response to being heated or cooled (or, in some cases, held isothermally). The goal is to establish a connection between temperature and specific physical properties of materials. The most popular techniques are those that are the subject of this book, namely differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomechanical analysis (TMA), dynamic mechanical analysis (DMA), dielectric analysis (DEA), and micro/nano-thermal analysis (p/n-TA). 

The micro-methods (differential-thermal analysis = DTA, differential scanning calorimetry = DSC) are quick and require little experimental effort, but they provide no means of adding reactants during measurements, and heterogeneous scunples cannot be mixed. All micro-methods use a twin (or differential) design to eliminate disturbing effects, i.e. an inert sample is exposed to the same environment conditions as the sample under investigation and the difference of the two heat flows is recorded. 

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