Differential scanning calorimetry, chemical

Development stage, life cycle issues, 20-23 Deviations, risk assessment, 94-95 Differential scanning calorimetry, chemical reactivity tests, 87... 

Chemical composition Atomic absorption, differential scanning calorimetry, others ... 

A number of analytical techniques such as FTIR spectroscopy,65-66 13C NMR,67,68 solid-state 13 C NMR,69 GPC or size exclusion chromatography (SEC),67-72 HPLC,73 mass spectrometric analysis,74 differential scanning calorimetry (DSC),67 75 76 and dynamic mechanical analysis (DMA)77 78 have been utilized to characterize resole syntheses and crosslinking reactions. Packed-column supercritical fluid chromatography with a negative-ion atmospheric pressure chemical ionization mass spectrometric detector has also been used to separate and characterize resoles resins.79 This section provides some examples of how these techniques are used in practical applications. 

A 100 Degree Rule was often used in the past throughout the chemical industry to assess whether an accident would occur. According to this rule, if the operating temperature of a process is 100 "C away from the nearest detectable exotherm observed in DSC (Differential Scanning Calorimetry) experiment the operation will not experience this thermal event. In such a case no more detailed information on hazards need be searched for. The 100°C degree rule is, however, often far from the safety margin The use of this rule was the reason of many accidents. 

Chemical structure of monomers and intermediates was confirmed by FT-IR and FT-NMR. Molecular weight distribution of polymers was assessed by GPC and intrinsic viscosity. The thermal property was examined by differential scanning calorimetry. The hydrolytic stability of the polymers was studied under in vitro conditions. With controlled drug delivery as one of the biomedical applications in mind, release studies of 5-fluorouracil and methotrexate from two of these polymers were also conducted. 

ASSESSMENT OF REACTIVE CHEMICAL HAZARDS COMPUTATION OF REACTIVE CHEMICAL HAZARDS DIFFERENTIAL SCANNING CALORIMETRY DIFFERENTIAL THERMAL ANALYSIS MAXIMUM REACTION HEAT REACTION SAFETY CALORIMETRY... 

Differential scanning calorimetry can also supply valuable information regarding solvate species, and it is particularly useful with respect to temperature and energetics of the desolvation process Two samples of the developmental compound L-706000-001T were shown to be chemically identical, and each contained two moles of water. The XRD powder patterns for the two samples were found to be quite different, demonstrating the existence of polymorphism... 

Based on the level of knowledge of chemical reactivity hazards, determine if additional screening of reactivity hazards is necessary. Having reactive functional groups might indicate the need to perform literature searches, access databases, or run differential scanning calorimetry. 

In differential scanning calorimetry, the selected chemical reaction is carried out in a cmcible and the temperature difference AT compared to that of an empty crucible is measured. The temperature is increased by heating and from the measured AT the heat production rate, q, can be calculated (Fig. 3.19). Integration of the value of q with respect to time yields measures of the total heats... 

Chemical reactivity test data produced by employers or obtained from other sources (e.g., differential scanning calorimetry, thermogravimetric analysis, accelerating rate calorimetry). 

Differential scanning calorimetry (DSC) Chemical testing technique that is used to establish... 

To use equation 2.10 correctly, we need to know how the heat capacities vary in the experimental temperature range. However, these data are not always available. A perusal of the chemical literature (see appendix B) will show that information on the temperature dependence of heat capacities is much more abundant for gases than for liquids and solids and can be easily obtained from statistical mechanics calculations or from empirical methods [11]. For substances in condensed states, the lack of experimental values, even at a single temperature, is common. In such cases, either laboratory measurements, using techniques such as differential scanning calorimetry (chapter 12) or empirical estimates may be required. 

The enthalpies of phase transition, such as fusion (Aa,s/f), vaporization (AvapH), sublimation (Asut,//), and solution (As n//), are usually regarded as thermophysical properties, because they referto processes where no intramolecular bonds are cleaved or formed. As such, a detailed discussion of the experimental methods (or the estimation procedures) to determine them is outside the scope of the present book. Nevertheless, some of the techniques addressed in part II can be used for that purpose. For instance, differential scanning calorimetry is often applied to measure A us// and, less frequently, AmpH and AsubH. Many of the reported Asu, // data have been determined with Calvet microcalorimeters (see chapter 9) and from vapor pressure against temperature data obtained with Knudsen cells [35-38]. Reaction-solution calorimetry is the main source of AsinH values. All these auxiliary values are very important because they are frequently required to calculate gas-phase reaction enthalpies and to derive information on the strengths of chemical bonds (see chapter 5)—one of the main goals of molecular energetics. It is thus appropriate to make a brief review of the subject in this introduction. 

C. T. Mortimer. Differential Scanning Calorimetry. In Thermochemistry and Its Applications to Chemical and Biochemical Systems M. A. V Ribeiro da Silva, Ed. NATO ASI Series C, Riedel Dordrecht, 1984 47-60. 

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