Differential Scanning Calorimetry and Thermogravimetric Analysis
(DSC-TGA) of Quail Egg Shell
M. Dzulfahmi Ramadhan – 6137442 SCCH/M
SCCH 778 Physico Chemical Technique (Aj. Siwaporn M. Smith)
Introduction
Thermal analytical techniques particularly have both diverse and dynamic in its
current field. Normally, almost any sample in chemical experiments whether its solid, semisolid or liquid can be analyzed and mainly characterized using thermal analytical techniques.
In general, materials such as food, pharmaceuticals, polymers, organic and inorganic
compounds can simply be measured the change of material properties in terms of function of
temperature. Thus allows researchers unable to access information related to matter theories,
for instance, equilibrium and irreversible thermodynamics and kinetics.
The basic principal of Differential Scanning Calorimetry (DSC), is simply derived from
DTA instruments, but DSC has different technique in allowing measurement of a change in
enthalpy. Controlled temperature applied in both sample and reference with no phase change,
increase or decrease, particularly will lead into a point that undergo a phase change.
Subsequently, this change can be determined as endothermic or exothermic process when
specific heating rate is applied (heating or cooling respectively), and the difference in
temperature can be also recorded. Heat flow recorded from DSC instrument is based on
equation of
𝑑𝐻
𝑑𝑇
= 𝐶𝑝
𝑑𝑡
𝑑𝑡
where H is amount of enthalpy evolved, Cp is heat capacity, T is the absolute temperature,
and t is time, thus it can be stated that dT/dt is the heating rate applied.
While thermal analysis using Thermogravimetric
Analysis allows measurement of changes in weight in
relation to changes in temperature. The measured weight
loss curve of specific sample will give information of
changes in sample composition, thermal stability and also
kinetic parameters for chemical reactions in the sample.
Theoretically, the mechanism of weight loss change in
TGA has particular scheme for each sample, it could be
decomposition, which is caused from breaking apart of
chemical bonds; evaporation, caused by the loss of
volatile compounds in sample after being applied within
elevated temperature; reduction, as the matter of interaction
atmosphere (hydrogen, ammonia, etc) and also desorption,
composition to be released out from the sample.
Figure 1. Thermobalance
scheme in TGA instrument
of sample to a reducing
which allows particular
Simultaneous TGA and DSC analysis
from a single sample has also been widely used
for time saving and convenient method of
thermal analysis experiments. This DSC-TGA
method measures both heat flow and weight
changes in a material as a function of
temperature or time in a controlled atmosphere.
Concurrent measurement of these two material
properties not only improves productivity but
also simplifies interpretation of the results. The
Figure 2. DSC-TGA
instrument design
complimentary information obtained allows
differentiation between endothermic and
exothermic events which have no associated weight loss, such
as melting and crystallization, and those which involving
weight loss.
Interpretation of DSC-TGA result may differ based on
typical case for each sample used. As the temperature sensitive
instrument can be controlled exclusively, the sample of solid,
semi-solid and liquid can be analyzed its properties such as
oxidative or thermal stability of materials, composition of
multi-component systems, melting and boiling points,
transition temperatures, heats of fusion and reactions, also
decomposition kinetics of materials as well.
In experiment, it is also possible to decomposition
Figure 3. Typical DSC-TGA
kinetics of some polymeric materials. When the sample is
Results for Various Case
heated using several different heating rate conditions will
allow change decomposition time scale for typical component. Applying high value of heating
rate causes the higher the given decomposition temperature becomes.
The Distributed Activation Energy Model can be used to estimate the activation
energy corresponds to the decomposition of materials for each thermal transition. Basically,
DAEM model assumes the existence of an infinite number associated with various activation
energy. This theory than become simpler with the help of Arrhenius equation, to be written
simply as
𝑎
𝑘0 𝑅
𝐸𝑎 1
ln ( 2 ) = ln (
) + 0.6075 −
𝑇
𝐸𝑎
𝑅 𝑇
where a is heating rate (K/s), Ea is activation energy (J/mol), k0 is frequency factor, R universal
constant (J/mol K), T is temperature applied in thermal transition.
Experimental methods
In this work, we use material sample of quail egg shell which contains of hard part
(presumably CaCO3) and soft part (maybe protein and moisture). This material was placed in
a small crucible pan with a half amount fill. The sample then was placed inside container that
connected through sensitive analytical balance. For temperature control, oxygen gas was also
applied during experiment at the ambient temperature, then scanned the sample in interval
of 25 – 800 oC. In this experiment, both sample and reference were applied different heating
rates as following number of 6, 8, 10, 15, 20 oC/min which normally caused weigh loss of some
composition of egg shell. The mass loss might be caused by typical process such as
evaporation, since we know that the sample may contain some water vapors, degradation,
decomposition, or even chemical reaction. DSC data analysis would allow us to get
information about specific temperature for crystallization and melting process of egg shell
components. While TGA would give information about thermal transition of material
decomposition of egg shell. The influence of heating rate and decomposition range will be
discussed using TG information later on.
Result and discussion
Thermal transition of quail egg shell component was typically represented with
decomposition process. As the main component of hard part of the egg shell is composed by
calcium carbonate elements, then proposed transitions for this component is written by
CaCO3 (s)
CaO (s) + CO2 (g)
This decomposition reaction gives conclusion that after high temperature applied during
heating process, calcium carbonate would decay gradually at some points to form white solid
of CaO along with the evaporation of CO2. Here in this experiment, we could get information
about decomposition from Thermogravimetric Analysis. When the temperature was heated
up with typical heating rate condition, first, the moisture began to vapored out from the
sample, which gave small percentage of weight loss. Secondly, around 500 oC the composition
degraded with larger number of weight loss which can be concluded that there were some
organic compounds decayed due to the higher temperature point. Then the decomposition
would lead into the removal of CO2 gases which occurred in the last step around 700 oC.
Therefore, composition of the sample has only about a half of total weight, which specifically
is CaO solid left. This hypothesis was also strengthened with the presence of white solid when
the thermal analysis process had already ended. And quantitatively, we can also get this
information from molecular mass ratio for calcium carbonate decomposition reaction. Even
we do not have the specific mass, we still can predict that the total of CaO may occur left in
the sample after decomposition is around 56% (CaO = 56 g/mol, CaCO3 = 100 g/mol). In fact,
actual value is obtained from TGA data which specifically give us information that if the value
of CaO left in the last thermal transition is higher, then there might be also another inorganic
compound that cannot be removed. While if the value of weight loss occurs higher than
normally does, it might be caused by some hydrate or organic compounds which typically
sensitive with the high temperature analysis. Thermal transitions occurred in this experiment
are summarized in table 1.
Heating rate
(oC/min)
6
8
10
15
20
1st transition
5.831
6.163
5.433
9.043
6.275
Water/moisture
Weight loss (%)
2nd transition
2.841
5.099
13.16
7.716
44.82
Organic compound
(protein)
3rd transition
40.14
38.12
34.01
36.70
21.73
CO2
Approximate
Residue (%)
50
50
47
45
27
CaO (s)
Table 1. Summarizes of thermal decomposition of quail egg shell components in various heating rates
The removal of CO2 has the main effect of this decomposition, which leading into high
value of weight loss (almost 40%). And the maximum weight value of CO2 can be removed
approximately 48% according to the molecular mass ratio. Heating rate gives the influence for
the decomposition process in terms of thermal transition. Theoretically, increasing heating
rate will cause the decomposition yield higher value. Hence it is can be optimally achieved
when applying optimum condition of heating rates. Nevertheless, if the heating rates is
increased further can cause the decomposition to result in small residue, this may because the
higher heating rate also possibly can make the kinetic energy of thermal transition to be more
than the composition could bear. As we can see, for quail egg shell sample which contains of
mainly calcium carbonate was degraded excessively when it comes to heating rate of 20
oC/min. The composition of residue obtained after thermal process is much lower than
expected, in this case, we can conclude that there was also some calcium oxide decayed from
the total composition.
Thermal transitions occurred in the quail egg shell decomposition are mainly divided
into two major process, which are crystallization, showed by peak up, and melting process
showed by peak down. For both two processes, there were no reaction but physical properties
change. The crystallization occurred from exothermic process which also proceed some
enthalpy differences in thermal transition, while the melting represented endothermic
process. The various heating rates applied in this experiment make it unable to calculate the
activation energy for each using The Distribution of Activation Energy Model (DAEM). On
the basic principle of Arrhenius equations, we can simplify DAEM in order to get the
approximate values of activation energy and the corresponding frequency factor, k0.
𝑎
𝑘0 𝑅
𝐸𝑎 1
ln ( 2 ) = ln (
) + 0.6075 −
𝑇
𝐸𝑎
𝑅 𝑇
DAEM equation unable approximation to be done from linear regression from various heating
rates and temperature. Once we pot ln(a/T2) versus 1/T for various heating rates at specific
thermal transition, we can get graph as following and then using linearization result, we can
calculate the activation energy E, from its slope, which defined by (-Ea/R), while the frequency
factor can be calculated using intercept quantitatively.
Figure 4. Graphic plot of DAEM Model to calculate the activation energy for each thermal
transition in various heating rates
Activation energy occurs for each crystallization and melting transition based on DSC
graph. Here we get the linear equation of y = -3981.2x + 2.9834 for the first transition and y = 5772.x -1.8389. After considering the gas constant R for calculation, the activation energy
obtained for crystallization process is 33.1 kJ/mol and for melting is 48 kJ/mol.
Conclusion
Simultaneous thermal analysis using DSC-TGA is considered to be used effectively to
observe physical properties of some materials. This instrument generally refers to one sample
and reference measurement using thermal energy application to measure both heat flow and
weight changes in a material as a function of temperature or time in a controlled atmosphere.
This hybrid method allows measurement to increase productivity and simplify interpretation
of the results. The complimentary information obtained allows differentiation between
endothermic and exothermic events which have no associated weight loss, such as melting
and crystallization, and those which involving weight loss. In this experiment quail egg shell
is mainly composed of few proteins and some calcium carbonate which is more dominant in
forming the shell to become hard and stiff. The decomposition of the sample was leading into
removal of moisture, organic compounds, and CO2 and leaving residue of CaO from TGA
data. While from DSC data, thermal transition occurred in two ways, exothermic
crystallization and endothermic melting process. In addition, activation energy for each
thermal transition also can be achieved using DAEM model, resulting 33.1 kJ/mol and 48
kJ/mol respectively.
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Differential Scanning Calorimetry Data
Thermogravimetric Analysis Data