My DSC data of starch with 5mg starch + 10 microliter of water showing a very sharp peak with onset temperature at 107.8 degree Celsius and peak at 114 and conclusion at 122.
Also the enthalpy was found to be very high(1194J/g)
The onset temperature of starch in DSC (Differential Scanning Calorimetry) can be high due to its complex structure and high molecular weight. Starch is a polysaccharide made up of glucose units linked together by glycosidic bonds. The structure of starch is highly organized and can form crystalline regions, which require a lot of energy to break apart during heating. Additionally, starch has a high molecular weight, which means that it requires more energy to break apart its intermolecular forces and undergo thermal degradation. Therefore, the onset temperature of starch in DSC can be relatively high compared to other materials.
Sir, thank you for the reply. In one journal where I sent this data they suggested that the onset temperature be lower than 105. They also pointed that enthalpy is too high. Is there any reason why it should not exceed 105?
What is the starting temperature of the reference material sample?
If the onset temperature of the sample is higher than the reference material, it will make it difficult to obtain accurate and reliable results.
maybe , the high enthalpy of
starch is due to the complex nature of its structure and the intermolecular forces that hold it together, as well as its degree of crystallinity and the presence of water molecules.
What kind of pan or container are you using? Is it open? Could it be that the peak you are observing may be the evaporation of water?
Rishibha Gupta desorption of surface water causes a broad endotherm (different from the sign of the DSC curve you found) that can start at temperatures lower than that found.
@Maria Betânia de Freitas Marques Thank you for the reply. I would like to add that before taking readings I had incubated my sample for 24 hrs so maybe surface water is less available.
This is the signal of water evaporation, check the weight lost of the pan before and after running the test, guess you will be able to get the a weightlessness right corresponds to the enthalpy (1194J/g). Try to scale up the signal of y axis before 100 degree C should fine new endothermic peak.
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