ultra violet spectroscopy

8/17/2019 Ultra Violet Spectroscopy

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M. Rashid Sarfraz Wattoo

M13-314

Ultraviolet spectroscopy


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ContextIntroduction

Types

Instrumentation

Process

Applications

Disadvantages

Research Article


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Introduction

Ultraviolet and visible (UV-Vis ) absorption spectroscopy is themeasurement of the attenuation of a beam of light after it passesthrough a sample or after reection from a sample surface.

This technique is used for :

etection of !unctional "roups.

etection of impurities.

#ualitative analysis

#uantitative analysis

$t helps us to sho% the relationship bet%een di&erent groups'it is useful to detect the conugation of the compounds

When molecules absorb energy, electronic transitions occur.


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Ultraviolet: 190~400nm.

Violet: 400 - 420 nm.

n!igo: 420 - 440 nm.

"lue: 440 - 490 nm.

#reen: 490 - $%0 nm.

&ello': $%0 - $($ nm.

)range: $($ - *20 nm.

+e!: *20 - %(0 nm.


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TYPES

ere are the tyes o/ this techniue accor!ing to the basic

henomena use! in each tye .

Absorbance :he light that interact 'ith the samle is absorbe! by it. his absorbe!

light is measure!. bsorbance sectroscoy is use! in the range o/

1*0 nm to %(0 nm.

Transmittance :3onochromatic light is /ocuse! on the samle an! the light 'hich

!ont absorbe! by it is !etecte! on the oosite si!e o/ the samle.


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Emmision :

When the molecules absorbe light, the electrons get e5cite!. When

the return to their groun! state, they relese light o/ 'avelenght eual

to that is absorbe!. n this case mostly !etectors are lace! at anangle o/ 90 !egree to the source light beam.


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UV-Visible 6ectroscoy

BEER-LAMBERT LAW

t is a uantitative relationshi to

!etermine the concentration o/

absorbing secie in solution.


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he relationshi A = εCl shows that the absorbance at acertain wavelength depends on concentration of sample.

A= Absorbance

ε = Molar Absorptivity

C = Concentration

L = path length


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#iters or Monochromators

ll monochromators contains the /ollo'ing comonents

n entrance slit .

!isersive !evice 8a rism or a grating

/ocusing lens . n e5it slit .

he /ilter or monochromator sen!s only monochromatic

light to the samle an! re/erence cell.


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ample containers *+ sample cells, variety of sample cells is available for UV region. The

choice of sample cell is based on

, path length ' shape ' sie

The transmission characteristics at the desired%avelength.

The cell holding the sample should be transparent tothe %avelength region to be recorded.

#uart or fused silica cuvettes are required forspectroscopy in UV region.

ilica te glasses can be used for the manufacture ofcuvettes for use bet%een /0 and 1000 nm. Thethic2nees of cell is generally 3 cm.


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etectors Three common types of detectors are used

i. 4arrier layer cell.

ii. 5hoto cell detectoriii. 5hotomultiplier ' photo voltic cells.


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s a m ! e

r e f e r e n c e

d e t e c t o r

I 0

I 0 I 0

I

log8I 0 I ; A

$%%&%%' nm

monochromatorbeam slitter otics

UV sources


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Process ,

or n to one o/ the t'o e5cite!

states 8= , or > .∗ ∗

(om!ounds )ith can*u"ated

doube bonds

he use/ul transitions i.e 200 nm-

400 nm are >?>@ /or the

conAugate! !ouble bon!.3oreover

n?=@ an! some >@ transitions.

+on con*u"ated com!ounds

Dienes an! lBenes usually have

absortion ma5ima belo' 200 nm.


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Process


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Remember !!!

As the number of multiple canjugated bonds in acompound increases the value of wavelenght also

increases at which the compound absorb light


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6&ect of solvent on pea2s>?>@ transitions lea!s to more olar e5cite! state that is more

easily stabiliDe! by olar associations 8 bon! . he >@ state is more

olar an! stabiliDe! more in olar solvent relative to non olar one .Eor n ;F > transition the n state is much more easily stabiliDe! by

olar solvent e//ects 8 bon! an! associations .

6o 'ith the stabiliDation o/ electronic transition the eaBs o/ sectra

also change . t means solvents can in!uce signi/icant changes in the

intensity o/ eaBs .


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Disadvantages

olvent should be

transparent to the speci7clight for sample.

amples should be insolution form.

8i9ture of substances

poses dicult toanalyse and requireprior separation.

lications

he molar bsortivity

)rganic chromosheres

bsortion by inorganic

grous

Glotting sectral !ata

Huantitative analysis


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/ Anasis of +ano (om!osite of 0##A (indrica 0(2

his bio nano comosit is a relacement to bone imlant.

t has been mo!i/ie! by calcium-carbonate to maBe a comosite o/

Ia-salt.

re!aration

t has been rein/orce! by novalac resin at 0 JI /or cross linBing.he comosite then /urther sonicate! at 40 JI /or 1 h to ro!uce "io-

nano comosites.

Weight ratio o/ Ia-carbonate to novalac resin is 1:1.

S!ectrosco! ncororation o/ resin an! carbonate ions into inner /iber sur/ace o/

bio nano comosite is con/irme! using UV sectroscoy.


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he UV- visible sectral analysis o/ all the comosites 'ere

carrie! out by UV 1*00 visible sectrometer in the 'avelength

range 200nm - (00 nm.

The s!actra

UV absortion sectrum o/ the samle sho's t'o large eaBs at

2(* nm an! $ nm 'hich sho's the resence o/ carbonate ions

in the comosite.

ultra violet spectroscopy

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