15ab1s0308
TRANSCRIPT
May 1, 2023 Vignan pharmacy college
DIFFERENTIAL THERMAL ANALYSIS & DIFFERENTIAL SCANNING
CALORIMETRY
Presented byS. LAKSHMI SRAVANTHI
(M. Pharm)15AB1SO308
Under the esteemed guidance ofA. MADHU SUDHAN REDDY
M.Pharm (Ph.D)Associate Professor
Department Of Pharmaceutics
VIGNAN PHARMACY COLLEGE(Approved by AICTE, PCI & Affiliated to JNTU KAKINADA)
VADLAMUDI, GUNTUR DIST, ANDHRA PRADESH, INDIA,PIN:522 2132015
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CONTENTS
1. Introduction
2. Differential thermal analysis
a. Principle
b. Instrumentation
c. Applications
3. Differential scanning calorimetry
a. Principle
b. Instrumentation
c. Applications
4. Conclusion
5. Reference
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Introduction Thermal analysis includes a group of techniques in which specific
physical properties of a materials are measured as a function of
temperature.
Theoretically, almost any substance whether solid, semi-solid or
liquid can be analyzed and characterized with thermal analytical
techniques.
Common materials include foods, pharmaceuticals, electronic
materials, polymers, ceramics, organic and inorganic compounds, even
biological organisms.
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DIFFERENTIAL THERMAL
ANALYSIS
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Differential thermal analysis is a
technique in which the difference
in temperature between a substance
and reference material is measured
as a function of temperature while
the sample and reference are
subjected to controlled temperature
programme.
PRINCIPLE
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If zero temperature difference b/w sample & reference
material sample does not undergo any chemical or physical
change.
If any reaction takes place temperature difference (∆T) will
occur b/w sample & reference material .
The Difference in temperature is called as Differential
temp(∆t) is plotted against temp. or a function of time.
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Phenomena causing changes in temperature
Physical changes:
• Adsorption (exothermic)
• Desorption (endothermic)
• A change in crystal structure
(endo – or exothermic)
• Crystallization (exothermic)
• Melting (endothermic)
• Vaporization (endothermic)
• Sublimation (endothermic)
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Chemical changes:• Oxidation (exothermic)
• Reduction (endothermic)
• Break down reactions
(endo – or exothermic)
• Chemisorption (exothermic)
• Solid state reactions
(endo – or exothermic)
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Differential Thermal Analysis (DTA) Instrument
Endothermic - heat flows into the sample.Exothermic - heat flows out of the sample.
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The various component of a DTA apparatus are as following:
1. Furnace Assembly: This is device for heating the sample.
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2.Sample and reference holder with Temperature detector
Sample holder- This is used to contain the
sample as well as the reference material.
Differential Temperature Detector- The function of this detector is
to measure differential temperature.
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Generally a low level DC amplifier is employed
3.Temperature programmerThe main function of this is to increase the temperature of the
furnace at a steady rate.
4. Amplifier and recorder
5. Recorder
6. Control Equipment -Its
function is to maintain a suitable
atmosphere in the furnace & sample
holder.
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Advantages:
• Instruments can be used at very high temperatures.
• Instruments are highly sensitive.
• Characteristic transition or reaction temperatures can be accurately determined.
Disadvantages:
• Uncertainty of heats of fusion, transition, or reaction estimations is 20-50%.
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Interpretation of DTA
ΔH = K * Peak area
K - can be determined by measuring the ΔH and peak area of know metals
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Factors affecting DTA curves
DTA is a dynamic temperature technique. Therefore, a large
number of factors can affect. These factors can be divided into
the three groups:
1. Instrumental factors
2. Sample factors
3. Environmental factors
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Instrumental factors
Furnace atmosphere
Furnace size and shape
Sample holder material
Sample holder geometry
Wire and bead size of thermocouple junction
Heating rate
Speed and response of recording instrument
Thermocouple location in sample
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Sample factors
Particle size
Thermal conductivity
Heat capacity
Packing density
Swelling or shrinkage of sample
Amount of sample
Effect of diluent
Degree of crystallinity
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• Effect of heating rate
on curve peak
resolution,
compound used was
cholesterol
propionate.
Heating rate
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• Effect of heating rate
on the peak
amplitude, compound
used was cholesterol
propionate.
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• Masking effect of sample peaks caused by diluent
(a) 8-quinolonol diluted
to 6.9% with carborundum
(b) 8-quinolinol diluted
to 5.9% with alumina
Effect of diluent
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• Effect of O2 and N2
atmosphere on the DTA
curve of a mixture of
2.5% lignite in Al2O3.
Environmental factors
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Limitations of Differential Thermal Analysis (DTA)
ΔT determined by DTA is not so accurate (2-3 ̊C).
Small change in ΔT cannot be determined and quantified.
Due to heat variation between sample and reference makes, it less sensitive.
To improve the above limitations change in the methodology is required.
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Applications
• Quantitative identification and purity assessment of
materials are accomplished by comparing the DTA curve
of sample to that of a reference curve.
• Impurities may be detected by depression of the M.P.
• Identification of substances.
• Identfication of products.
• Quantitative analysis
DTA peak curve is proportional to the total heat of
reaction and hence weight of the sample.
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DTA technique has been widely used for the quality control of a
large number substances like cement , glass, soil, catalysts, textiles,
explosives, resins.
DTA has been used to study the oxides of uranium and plutonium.
DTA investigations have been carried to help detection, purity
determination and quantitative analysis including the evaluation of
kinetic parameters of polymers, explosives, pharmaceuticals, oils, fats
and other organic chemicals.
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Differential Scanning Calorimetry (DSC)
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Principle
The sample and reference are maintained at the same
temperature, even during a thermal event in the sample.
• The energy required to maintain zero temperature difference
between the sample and the reference is measured.
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• Conventional DSC
Metal 1
Metal 2
Metal 1
Metal 2
Sample Empty
Sample Temperature
Reference Temperature
Temperature Difference = Heat Flow
•A “linear” heating profile even for isothermal methods
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• A DSC apparatus is built around
- a differential detector- a signal amplifier- a furnace- a temperature controller- a gas control device- a data acquisition device
Diagram of a DSC apparatus
Sample Reference
Gas control
Furnace controller
four
Data acquisition
Microvolt amplifier
Detectors
Furnace
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Differential Scanning Calorimeter(DSC) Heat flux
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Sample and reference holders• Al or Pt pans placed on constantan disc.
• Sample and reference holders are connected by a low-resistance
heat flow path.
Sensors• Chromel® (an alloy made of 90% nickel and 10% chromium)-
constantan area thermocouples (differential heat flow).
• Chromel®-alumel (an alloy consisting of approximately 95%
nickel, 2% manganese, 2% aluminium and 1% silicon)
thermocouples (sample temperature).
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Thermocouple is a junction between two different metals that
produces a voltage due to a temperature difference
Furnace• One block for both sample and reference cells
Temperature controller• The temperature difference between the sample and reference is
converted to differential thermal power, which is supplied to the
heaters to maintain the temperature of the sample and reference at
the program value
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Power Compensation DSC Cell
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Sample holder • Aluminum or Platinum pans.
Sensors• Platinum resistance thermocouples.
• Separate sensors and heaters for the sample and reference.
Furnace• Separate blocks for sample and reference cells.
Temperature controller• Supply the differential thermal power to the heaters to maintain
the temperature of the sample and reference at the program value.
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Modulated Temperature – DSC (MT-DSC)
This new technique introduced in 1993 has been thoroughly examined.
Polymer blends difficult to evaluate by conventional DSC have been
successfully analysed by modulated DSC
Main advantages are the separation of overlapping events in the DSC scans.
In conventional DSC, a constant linear heating or cooling rate is applied.
In modulated DSC (MDSC), the normally linear heating ramp is overlaid
with a sinusoidal function (MDSC) defined by a frequency and an amplitude to
produce a sinusoidal shaped temperature vs. time function.
Using Fourier mathematics, the DSC signal is split into two components: one
reflecting non-reversible events (kinetic) and the other reversible events.35
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It has been recently applied for the determination of glass transitions
of hydroxypropylmethylcellulose films and for the study of amorphous
lactose, as well as for the study of some glassy drugs
Micro-DSC
The instruments of conventional DSC allows to measure very
small amounts of material.
New instrument generation will permit to increase sensitivity
and amount of material to be studied decrease to nanorange.
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DSC Thermogram
Temperature
Hea
t Flo
w - >
exo
ther
mic
GlassTransition
Crystallisation
Melting
Cross - Linking(Cure)
Oxidation
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Main Sources of Errors
• Calibration• Contamination• Sample preparation – how sample is loaded into a pan• Residual solvents and moisture.• Thermal lag
• Heating/Cooling rates• Sample mass
• Processing errors
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Sample preparation
Form of sample: bulk solid, powder (pressed), liquid.
Amount of sample: 3-5mg.
DSC Pan: Al, Pt, stainless steel, Ag, Cu, Al2O3
Al Pt alumina Ni Cu quartz
* Small sample masses and low heating rates increase resolution
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Sample Preparation : Shape• Keep sample as thin as possible (to minimise thermal
gradients)• Cover as much of the pan bottom as possible• Samples should be cut rather than crushed to obtain a
thin sample (better and more uniform thermal contact with pan)
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Typical TGA and DSC Results for Various Transitions
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Modern Approach to Research by DSC and its Advancements
MEMS – DSCIt has been applied in manufacturing 3-D silica based structures with
specific geometrical, mechanical and electrical characteristics to operate
certain functions.
Analysing structural transitions of biological molecules in liquid phase
this is not workout with conv.DSC.
IR- heated DSCIt is a heat flux DSC, that comprises of a DSC sensor assembly for
receiving a sample that is installed in a cavity within an elongated cylinder
and an IR lamp assembly that is disposed of circumferentially around the
elongated cylinder with a length approximately similar to that of the cylinder.
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MTDSC
MTDSC provides the amplitude and phase signals i.e. altering signals and
the total heat-flow signal equivalent to that given by DSC simultaneously in
a single experiment. Highly advanced and fast technique.
GFMDSC
GFMDSC modulates a DSC by setting the properties of a gas in thermal contact
With the sample and the reference in the calorimeter.
High accuracy and high efficient
PNDSC
It is PCDSC that included the plurality of cell structures being used to
define a selective region for calorimetric measurements of nanomaterial. It
provides reproducible results.
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ApplicationsPolymer industry
Food industry
Pharma industry Research and development
Ceramic industry
Cosmetic industry
V.S.Marakatti et. al .RSC Adv., 2013,3, 10795-10800
Stability of the Materials
Sn(OH)Cl - Catalyst
200 ̊ C- Dehydration
200-400 ̊ C- Dehydroxylation
400-550 ̊̊C – Formation of oxide
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Application in determination of phasetransition
113 ̊ C Rhombohedral to monoclinic
124 ̊C Melting point
179 ̊CLiquid phase transistion
446 ̊CBoiling point
Sulfur element
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Polymorphism
DSC has proven to be very useful in the identification of polymorphic
transitions primarily due to the ability to easily study the sample under various
heating and cooling conditions needed to induce the polymorph formation.• Glass transitions• Melting and boiling points•Crystallization time and temperature•Percent crystallinity•Heats of fusion and reactions•Specific heat capacity•Oxidative/thermal stability•Rate and degree of cure•Purity
DSC also measures
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Conclusion
As formulations become more and more complex and
characterizing them becomes more difficult, manufacturers have
done an excellent job in keeping pace with more precise and
sensitive yet more durable instruments.
The applications discussed in this review represent a tiny fraction
of what is currently being done and with continual advances in the
field.
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REFERENCES
1) Ashish Chauhan & Bharti Mittu , Modern approaches to research
by DSC and its advancements, Pharmaceutica Analytical Acta,
Vol. 3, Issue 8, 2012.
2) Steven P. Stodghill, Thermal Analysis – A Review of Techniques
and Applications in the pharmaceutical sciences, 2010.
3) Bhupendar kumar*, Monish Sharma, Ramchandra, A Review on
Instrumentation of Thermal analysis method: DTA,DSC.
4) Gurdeep R. Chatwal, Sham K. Anand, Instrumental methods of
Chemical analysis, 5th edition, pg.no:2.719-2.753.
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THANKS TO ALL