15ab1s0308

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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May 1, 2023 Vignan pharmacy college 2

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


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.


DIFFERENTIAL THERMAL

ANALYSIS


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


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.


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)


Chemical changes:• Oxidation (exothermic)

• Reduction (endothermic)

• Break down reactions


• Chemisorption (exothermic)

• Solid state reactions



Differential Thermal Analysis (DTA) Instrument

Endothermic - heat flows into the sample.Exothermic - heat flows out of the sample.


The various component of a DTA apparatus are as following:

1. Furnace Assembly: This is device for heating the sample.


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.


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.


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%.


Interpretation of DTA

ΔH = K * Peak area

K - can be determined by measuring the ΔH and peak area of know metals


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


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


Sample factors

Particle size

Thermal conductivity

Heat capacity

Packing density

Swelling or shrinkage of sample

Amount of sample

Effect of diluent

Degree of crystallinity


• Effect of heating rate

on curve peak

resolution,

compound used was

cholesterol

propionate.

Heating rate


• Effect of heating rate

on the peak

amplitude, compound

used was cholesterol

propionate.


• 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


• Effect of O2 and N2

atmosphere on the DTA

curve of a mixture of

2.5% lignite in Al2O3.

Environmental factors


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.


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.


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.


Differential Scanning Calorimetry (DSC)


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.


• 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


• 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


Differential Scanning Calorimeter(DSC) Heat flux


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).


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


Power Compensation DSC Cell


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.

May 1, 2023Vignan pharmacy college

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


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.


DSC Thermogram

Temperature

Hea

t Flo

w - >

exo

ther

mic

GlassTransition

Crystallisation

Melting

Cross - Linking(Cure)

Oxidation


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


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


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)


Typical TGA and DSC Results for Various Transitions


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.


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.


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


Application in determination of phasetransition

113 ̊ C Rhombohedral to monoclinic

124 ̊C Melting point

179 ̊CLiquid phase transistion

446 ̊CBoiling point

Sulfur element



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


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.


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.


THANKS TO ALL

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