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 SIMULTANEOUS THERMAL

 ANALYSIS AND EVOLVED GAS ANALYSIS 

Firdous qureshiMsc 2

Paper 3

Unit 4

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SIMULTANEOUS THERMAL

ANALYSIS Simultaneous thermal analysis (STA) generally reers to the

simultaneous application o thermogra!imetry(T"A) and dierential

scanning calorimetry(#S$) to one and the same sample in a single

instrument%

Simultaneous T"A&#S$ measures 'oth heat lo (#S$) and eightchanges (T"A) in a material as a unction o temperature or time in a

controlled atmosphere%

Simultaneous measurement o these to material properties not only

impro!es producti!ity 'ut also simpliies interpretation o the results% The complimentary inormation o'tained allos dierentiation

 'eteen endothermic and eothermic e!ents hich ha!e no associated

eight loss(melting and crystalli*ation) and those hich in!ol!e a

eight loss(degradation)%

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• The simultaneous application o thermogra!imetry (T"A) and

dierential scanning calorimetry(#S$) to a single sample in a STA

instrument yield more inormation than separate application in to

dierent instrument+

• The test conditions are perectly identical or the T"A and #S$

signals(same atmosphere,lo rate ,!apour pressure on the

sample,heating rate, thermal contact to the sample cruci'le andsensor,radiation eect,etc)

• The analy*a'ility o the signals is impro!ed,since to or more sets

o inormation concerning sample 'eha!iour are alayssimultaneously a!aila'le(dierentiation 'eteen phase

transormation and decomposition,'eteen addition and

condensation reactions, recognition o pyrolysis,oidation and

com'ustion reaction etc)

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 PRINCIPLE OF EVOLVED GAS

 ANALYSIS 

-./0.-# "AS A1A0SS is a technique in

hich the nature or amount o gas e!ol!ed rom

the sample is monitored against time or

temperature%

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WHY EGA???

  T"A pro!ides inormation a'out+

eight changes as a unction o temperature or time

#ecomposition temperature

56ut it cannot identiy the gaseous products in!ol!ed77 

T"A tells u hen and ho much 'ut not hat came o88

hat came o is important 'ecause88

t eplains reaction mechanism

t tells you hat the reaction 'yproducts are

t tells you hich sol!ents are present

t allos a greater understanding o the decomposition

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 Hyphenated EGA techn!"e

TG#MS 

TG#FTIR

TG#GS$MS 

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 POSSI%LE GAS ANALY&ER

"as chromatography

Mass spectrometry Thin layer chromatography

Titrimetry

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GAS CHROMATOGRAPHY 

n this technique the sample under study is heated in anelectric urnace%

A suita'le carrier gas is passed to urnace at constant

 pressure and outlet o the carrier gas rom urnace is

directly connected to "%$ column%

hen sample is heated,as long as no decomposition

starts,it leads to the e!olution o certain gases%

This gas ill 'e sept 'y the carrier gas and ill reachto the "%$ detector hich ill sho signal or pea9%

Position o pea9 correspond to type o gas coming rom

the column hereas the area under pea9 gi!e the amount

o gases coming rom the column

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 Dec'(p')t'n '* ca+c"( ',a+ate

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TITRIMETRY 

Amount o gas e!ol!ed can 'e determined 'y continuous

titration%

The e!ol!ed gas rom pyrolysis cham'er is transered toa'sor'ing solution here it is continuously titrated%

Titrant used depend upon the type o gas to 'e determined%

e%g% ammonia is titrated ith dil% :$l and ater isdetermined 'y 9arl icher method%

$ompounds that can 'e determined includes ater :$l ,

 1 , $$%  

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 MASS SPECTROMETRY 

t is the most idely used technique employed in analysis o

e!ol!ed gas%

This technique gi!e positi!e identiication o the gases

e!ol!ed during thermal reaction%

-!ol!ed gases rom the pyrolysis cham'er , #TA apparatusor thermo'alance can 'e introduced directly into the mass

spectrometer%

-"A&MS technique is a linear programmed heating o the

sample in the !accum cham'er o the mass spectrometer

scan mass range%

onic mass may 'e monitored as a unction o time or

temperature o pyrolysis%e%g% copper sulphate pentahydrate

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 Dec'(p')t'n '* c'ppe- )"+phate

 pentahyd-ate

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 INFRARED SPECTROSCOPY 

ield inormation on the composition(a'sorption 'ands) o the

e!ol!ed gases%

Ad!antages+

• -asy detection o hydrocar'on

• ;eal&time detection o temperature dependent gase!olution%

#isad!antages+

•

 1o detection o inert gases%• #etection o inorganic gases limited%

• #etection aected 'y ater !apour%

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