Samples hermetic pans

FIGURE 2.3 Comparison of three samples of indium, of varying mass, heated at 10°C/min. Hermetic pan with inverted lid. Nitrogen purge gas at 25 ml/min. Heat flow plotted against temperature. 

With some types of hermetic pans, the lid may be inverted and placed into the sample pan. This is ideal for running smaller samples as it produces an hermetic pan with a smaller dead volume above the sample, and improves heat transfer to the top of the sample. For very small samples two pans may be used, one inverted and pushed inside the other. This type of configuration is also good for sealing 2 to 3 mg of calibration sample and keeping as a retained standard. 

Liquid samples, if heated to too high a temperature, will burst the pan open when the pressure exceeds around -300 kPa for aluminum hermetic pans and -600 kPa for gold pans. If higher temperatures or pressures are required, the use of a large volume stainless steel capsule to hold the sample is recommended. Another solution to this problem is to pierce the lid of the pan to enable volatile components... 

Typical volume is -100 pi If the sample reacts with stainless steel use an aluminum hermetic pan to hold sample alternatively, use a glass ampoule... 

Some evidence of a Tg in this range has been obtained and this has been detailed elsewhere (9). The most persuasive evidence has been foimd in the DSC curves of some samples where there are endotherms which could be attributed to physical aging after the Tg had been lowered because of plastidzation by absorbed moisture. A typical result is seen in Figure 3 when the dehydration of PPy/p-TS is suppressed in hermetic pans a typical aging endotherm precedes the loss of water (Figure 3, curves b and c) and this can be enhanced by suitable annealing. Also, instead of the usual broad endotherm (Figure 3, curve a) obtained for fresher material in open pans, some other older samples of different PPy film have shown an additional sharp endotherm (between 60 and 90 O superimposed on the expected DSC curve. 

A TA Instruments DSC 2920 (TA Instruments, New Castle, Delaware) was used to study the thermal properties and crystallinity of the microgels. Microgels with excess squalane were sealed in an aluminum hermetic pan and cooled to 0 °C in the DSC cell before being heated at a rate of 10 °C/min to 155 °C. Following this, the sample was brought back to -40 °C with a cooling rate of 10 °C/min and this process was repeated for an additional seven cycles. 

Glass transition temperatures (Tg s) were detemined using a Dupont DSC 910 attached to a 9900 data analysis system. For off-stoichiometric studies, epoxy resin and diamine were cured in situ within a hermetically sealed DSC pan (sample tak from 25 C - 300 C at lO C/min), then cooled rapidly back to 25 C, and finally scanned from 40 C - 220 c to record the Tg. All samples were scanned under nitrogen atmosphere at a rate of 10 C/min. 

Use forceps to handle the sample pan and lid. Obtain the tare weight of a sample pan and lid (the type that can be hermetically sealed is not required). (Note Select pans with flat undistorted bottoms so that good contact with the cell platforms is assured.)... 

The sample containers most commonly used are cylindrical pans pressed from pure aluminium foil. Alternative materials are used for very high temperatures or corrosive substances, and hermetically sealed pans to withstand several atmospheres pressure can be used for volatile materials. Some heat flux DSC instruments are available which are capable of operation at high pressures, by means of containment of the DSC cell within a pressure vessel. 

The DSC of etodolac and its solid dispersions in propylene glycol were performed by heating the samples in a hermetically sealed aluminum pan at a heating rate of 10°C/min over the range of 20-300°C [11]. The thermograms of etodolac and PEG 6000 solid dispersions, and physical mixtures were similar, indicating the absence of chemical or physical interactions between the components. 

In any DSC instrument, the sample and reference material are placed in small individual pans or crucibles, which may be open or hermetically sealed, of 10-20 p,L capacity (Harwalkar and Ma, 1990). Sample size is... 

The thermal behavior of ot-chitin was examined by differential scanning calorimetry (DSC) using a DSC-25 Mettler instrument. Samples (each 5 mg) were hermetically sealed in aluminum pans and scanned over a temperature range of 0-350 °C at a scan rate of 5 °C/min. The instrument was calibrated using indium, and the calorimetric data were analyzed using STAR software (version 9). 

Differential scanning calorimetry Samples of gels (8 to 11 mg) were placed in hermetically sealed stainless steal pans and analyzed with a DSC QlOO (TA Instruments, New Castle, DE, USA). An empty pan was used as reference. Samples were heated at 10°C/min from -40 to 120°C. At least triplicate samples were analyzed for each gel. The endothermic melting peak around 0°C was taken as an evidence of ice melting. Endothermic peaks in the 50 to 70°C range were taken as evidence of starch retrogradation (stored samples). 

For DSC analysis, samples of about 10 mg conditioned in hermetic TA aluminum pans were heated at 10°C/min, between —120 and 100°C, in inert atmosphere (45 ml/min of N2) in a DSC TA2010 controlled by a TA5000 module (TA Instruments, New Castle, DE). The reference was an empty... 

Low-viscosity liquids can be transferred to the hermetic DSC pan using a Pasteur-pipette or similar apparatus. Dipping one end of an opened paper clip into viscous liquids and then placing it onto the base of the sample pan may transfer higher viscosity samples. Care should be taken not to contaminate the lip of the pan with any liquid as this will result in a poor seal. 

Samples are loaded into pans for DSC analysis. Pan configuration (open, crimped, hermetically sealed, hermetically sealed with a pinhole, etc.) and scan rate can result in variations in position and intensity of the thermal events. These variations can be used to gain further information about the sample as well as other crystal forms. 

A wet sample was hermetically sealed in a sample pan. The empty sample pan and the sealed pan were weighed. The sealed pan was quickly frozen Inside the DSC chamber to -40 C and several minutes were allowed for the system to come to equilibrium. The sample holder assembly was then heated at a rate of 5 C/mln. A scanning speed of 5 C/mln was found to give the optimum values of peak height and peak spread. This minimized the errors In experimental measurements. After the DSC measurement, the pan was punctured... 

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