Instrumental Analysis in Surface, Polymer and Nanoscience.

Instrumental Analysis in Surface,

Polymer and Nanoscience

Course 3130, Dr. Lokanathan Arcot

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Defining a surface

MacroscopicResolution > mm

Microscopic Resolution µm, nm

Atomic scaleResolution Å

Top 2-3 atomic layers


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Defining a polymer

Large molecules formed by joining well defined monomeric repeating units

http://medical-dictionary.thefreedictionary.com/monomer

ProteinMonomer: Amino acids

Linear polymer


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Examples of linear polymers

PolysaccharideMonomer: sugar units

Cellulose polymerCellobiose monomer

http://www.wikihow.com/Understand-DNA-Structure

Nucleotide

DNA(Single strand shown here)

Polynucleotide(DNA)

Monomer: nucleotide


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Defining a nanomaterial

’2’ D NanomaterialThickness in nm range

Example: Thin films

Any material with at least one of its dimensions in the range 1-100 nm

’1’ D NanomaterialBreadth and Width in nm range

Example: Nanorods, tubes

’0’ D NanomaterialL, B and H in nm range

Example: Nanoparticles, Viruses


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Why should we study

• Surfaces

• Polymers

• Nanomaterials


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Why study surfaces?

Biomedical Surface – water interaction

Food industry

Metal corrosion


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Why study polymers?Thermal Mechanical

Electrical-electronic

1500 °C

Plastic utilities


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Why study Nanomaterials?

Biomedical

Semiconductor tech.50 nm

Power storage/generation

Fuel cells

Antibacterial.


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What kind of information we need to know ?

- surfaces

- polymers

- nanoparticles

General properties

Specific properties

e.g. composition

e.g.

Surface – roughness

Polymer – MW, conformation

Nanomaterials – aspect ratio


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General chemical information - I

Chemical compositionElemental composition – e.g. C, O, N

Organic Vs. Inorganic – Fe, Na, Ca, K, Cl, S,

Oxidation state/chemical bonding information –

e.g. C3H8O

Qualitative : e.g. Is Carbon present or not?

Vs. Quantitative : e.g. How much of carbon is present?

%, empirical formula


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General chemical information - II

Functional groupsReactive groups

- COOH, - NH2, - OH, -SH,

Ionizable groups (charge +ve or –ve)

–ve – COO -, -SO3-, -PO4

-

+ve – NH3+


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General chemical information - II

What kind of information we need to know ?

General chemical information - I

We use various ’METHODS’ to get the information we need

Analytical Methods


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Analytical methodsDestructive Methods

Sample is chemically transformed as a result of measurement technique or as a part of sample preparation procedure in order to enable the measurement

Non-destructive MethodsSample is analysed in it’s pristine (unaltered) form

without chemical/physical damage

DiscussionAdvantages Vs. disadvantages

How would you make choice between destructive and non-destructive?


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Classification of Analytical MethodsClassical MethodsQualitative analysis performed by separation

Precipitation, distillation (may involve analyte conversion)Identification by using color, melting point

Quantitative analysisVolumetric, gravimetric

Instrumental MethodsAnalysis types : (few examples)

Light absorption (at specific wavelength)Light emissionFluorescence (a type of photoluminiscence)Mass to charge ratioElectric potential related chemical conversion

Further reading: Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Page 1-2


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Performance of analytical methodsImportant characteristics Figures of merit: They permit us to narrow the choice of instruments for a given analytical problem to a relatively few.

Further reading: Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Page 18-22http://www.wfu.edu/chemistry/courses/jonesbt/280L/Intro%201/FOM.pdf

PrecisionAccuracySensitivityDetection LimitDynamic RangeSelectivity

Example: Weighing machine

Sample (Weight)

Electrical signal / Spring compression

Display/Pointer


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Figures of Merit

Further reading: Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Page 18-22http://www.wfu.edu/chemistry/courses/jonesbt/280L/Intro%201/FOM.pdf

Accuracy

Precision

Sensitivity

Detection Limit

Dynamic Range

True weight (WT)1.000 kg

0.995, 1.002, 1.003 0.8, 1.0, 1.1

Average 1.000 Average 0.967

Std dev ± 0.004 Std dev ± 0.157

Minimum difference 0.001 Minimum difference 0.1

Lowest 0.01 Lowest 0.2

0.01 – 9.90 0.2 – 4.8


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Instrument response

Sample property(Weight / concentration / temperature)

LOQ LOL

LOQ LOL

Dynamic range

Comparing Performance: Dynamic Range

Lower range

Higher range

LOL – Limit of Linearity; LOQ – Limit of Quantitation

Method 1

Method 2


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Instrument response

Sample property(Weight / concentration / temperature)

Comparing Performance: Sensitivity

Higher slope Higher sensitivity

Lower slope Lower sensitivity

Method 1

Method 2

Higher slope meanshigher response per unit change in sample property, hence higher sensitivity


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Choosing a Method

Accuracy: How close is measured value to true value.

Precision: How close the measured values are to each other

Sensitivity: Ability to discriminate between small difference

Detection Limit: Minimum value that can be detected

Dynamic Range: Useful range of analytical method

Selectivity: Degree of interference from other species/factors

Other Characteristics:Speed of measurement, Cost and availabilityEase and convenience


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Quantitative analysisVolumetric, Gravimetric

Instrumental MethodsAnalysis types : (few examples)

Light absorption (at specific wavelength)Light emissionFluorescence (a type of photoluminiscence)Mass to charge ratioElectric potential related chemical conversion


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A short break


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Volumetric Titrations – Photometric – Potentiometric

GravimetricThermo-gravimetric analysis


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Elemental Analysis (Basic)

A selective basic elemental analysis’CHNS analysis’

Chemical compositionElemental composition – e.g. C, O, N

Organic Vs. Inorganic – Fe, Na, Ca, K, Cl, S

Materials of biological origin – C, H, N, O, S

More sophisticated universal elemental analysis - XPS


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Setup for ’CHNS analysis’

Combustion

Reduction

Mixing

Separation Detection

Schematic modified from http://www.perkinelmer.com

O2

He


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Setup for ’CHNS analysis’

CombustionO2 99.9%

He – Carrier gas> 1000° C

+Oxidation WO3

CHNS

CO2

H2ONOx

SO3

Reduction

Copper aided

Removal of excess O2

NOx

SO3

CO2

H2ON2

SO2

Mixing

SeparationGas

Chromatography

CO2, H2O, N2, SO2

Removal of all other products, Cl

Detection

Separated gases passed through- Thermal cond-

uctivity - Infrareddetectors

Time

Conc.

Oxygen estimation: (different mode)During combustion: No O2 , Sample O2 converted to CO over Platinized Carbon


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Example of CHNS analyser

DiscussionWhat to look for?

Go to previous slide


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http://www.rsc.org/images/CHNS-elemental-analysers-technical-brief-29_tcm18-214833.pdf

http://www.perkinelmer.com/CMSResources/Images/44-74386BRO_2400_SeriesII_CHNSO_Elemental_Analysis.pdf

http://cmet.gov.in/?q=prototype_chns.html

References for CHNS analysis


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Thermogravimetry

Instrumental Methods of Chemical Analysis, by Kaur. H, 2010, Chapter 41

A technique in which a change in the weight of a sample is recorded as a function of temperature or time

Typical setup Combined Thermal Instruments

Quantifying products of thermal

decomposition

CO2, H2O, NOX, SO3

Chemical analyser


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Thermogram

Integrated Waste Management - Volume I, book edited by Sunil Kumar, ISBN 978-953-307-469-6

TGA- ThermoGravimetricAnalysisDTG- DerivativeThermoGravimetric analysis

𝑑𝑊𝑑𝑇𝑖𝑚𝑒


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Application of Thermogravimetry Treatment of CuSO4 .5H2O

Instrumental Methods of Chemical Analysis, by Kaur. H, 2010, Chapter 41

TGADTG

H2O SO2, O2

Information derived as a func. of Temp.Weight of gaseous productIdentity of products


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Application of ThermogravimetryAnalysis of Mixtures: Ca, Ba, Sr oxalates

What info is needed to analyse a mixture of these?

Thermal analysis of pure oxalates

450 – 560 °C

420 – 590 °C

350 – 420 °C 660 – 840 °C

> 1000 °C

820 – 960 °C


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Thermogram of mixture: Ca, Ba, Sr oxalates

http://ruc.udc.es/bitstream/2183/11497/1/CC-80%20art%206.pdf

H2OCO (all converted to CO3)

CO2

CO2

Calculations:Step C: Weight of CO2 produced is measured

All of that CO2 came from Ca CO3

From CO2 amount we can tell amount of Ca CO3

From the amount of Ca CO3 we can calculate amount of CaLikewise Step D and E will give us amout of Sr and BaFinally the composition of mixture of Oxalates


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Application of Thermogravimetry in renewable material analysis

Chem. Soc. Rev., 2012, 41, 8075-8098


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Aim of their study

To develop an alternative to ’extractive’ way of detemining the composition (lignin, cellulose, hemi-C) in biomass

Solution: Thermal Analysis

Biomass and Bioenergy, 35 (2011) 298-307


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Agriculture 2013, 3, 12-32; doi:10.3390/agriculture3010012

TGA of Wood (Oak Red)

Research Article

Title: Pyrolysis Kinetics of Physical Components of Wood and

Wood-Polymers Using Isoconversion Method

By: Wenjia Jin, Kaushlendra Singh and John Zondlo

Agriculture 2013, 3, 12-32;

How to analyse a mixture of Cellulose, HemiC, Lignin?

Thermal analysis of pure components


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Thermogram and DTG of pure components of Wood



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Peak fitting components into DTG


Temperature

Peak fitting done using the knowledge obtained from peak shape, position of pure DTG




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Peak fitting components into DTG


Temperature

We have a set of values of ’areas’ for known values of ’weights’CALIBRATION PLOT


Weight from Extractive methods

Area from DGT


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Calibration Plot – Cellulose and Hemicellulose

Area

Weight (mg)

Hemice

lluos

e

Cellulose

Unknown SampleRecord TGA, DTGFit components Measure area of componentFind weight - Calibration plot



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DTA – Differential Thermal Analysis

DSC – Differential Scanning Calorimetry

Other important Thermal Analysis methods


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1. Gravimetry – Analytical Chemistry by Higson, SéamusPublisher: Oxford University PressCopyright Date 2004 ISBN 978-0-19-850289-0 Electronic Isbn 978-1-61583-964-3

2. Instrumental methods of chemical analysis by H. Kaur. Publisher Pragati Prakashan Date 2010

3. Principles of Instrumental Analysis, by, Holler, Skoog, Crouch, Chapter 31

4. Biomass and Bioenergy, 35 (2011) 298-307

5. Agriculture 2013, 3, 12-32

References for TGA


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Volumetric Titrations – Photometric – Potentiometric


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Titrations – Conductometric

Classical Volumetric Titration

Analyte – The chemical group we wish to estimate

Titrant – solution containing known conc. of chemical reactive towards analyte stoichiometrically

Indicator – A means to indicate the complete consumption of Analyte

Titration

Analyte +Indicator

Analyte +

Indicator

Titrant Titrant is added in small volumes until Analyte is consumed


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Types of Titrations

Estimation of Base

Estimation of Acid


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Example of Acid-Base Titration

HCl + NaOH NaCl + H2OAnalyte Titrant

AnalyteHCl

TitrantNaOH

pH

OrEnd Point


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End-point of Acid-Base Titration

Phenolphthalein Indicator

Excess OH –

8.2-12

Excess H+

0-8.2


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Acid-Base Titration (Ions in solution)

H + + Cl – Na + + Cl – Na + + OH – Acidic

mediumEnd point Alkaline

medium

H+ replaced by Na+ Na+, OH– added

Conductance of a solution depends on mobility of ions


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Acid-Base Titration (Ionic conductivity)

Conductance

Volume of Alkali added

Excess acid

Excess base

End-point

Ionic conductivity can be used to follow titrations

- Conductometric Titration


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Setup for Conductometric Titration

http://www.tau.ac.il


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www.metrohmsiam.com

Other types of Titrations


53www.metrohmsiam.com

Other types of Instrumental Titrations


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1. http://www.metrohmsiam.com/petrochemist/PC_23/PC23_Monograph_955428_80165003.pdf

2. http://www.tau.ac.il/~advanal/ConductometricTitrations.htm

http://www.metrohmsiam.com/petrochemist/PC_23/PC23_Monograph_955428_80165003.pdf





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Summary

• Definition of Polymer, Surface, Nanoparticle

• Chemical Composition

• Classification of Analytical Methods

• Performance of Analytical Methods (Figures of Merit)

• Classical Methods

CHNS Analysis

ThermoGravimetric Analysis

Conductometric Titration

Instrumental Analysis in Surface, Polymer and Nanoscience.

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