spectrophotometry report5

8/9/2019 spectrophotometry report5

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BY:

Miralyn Madel Abapo

Agnes Fay Uayan

Rubee Bagaipo

Haviv Russel Solis

Jenevy Gido


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Spectrophotometry

quantifiable study of electromagneticspectra.

more specific than the generalterm electromagnetic spectroscopy in

that spectrophotometry dealswith visible light, near-ultraviolet, andnear-infrared.


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Types of Spectrophotometry

ATOMICABSORPTION

SPECTROPHOTOMETRY

FLAMESPECTROPHOTOMETRY


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AtomicAbsorption Spectrophotometer

Used to measure concentration by atoms rather

than by molecules

atoms in the ground state absorb the light of

characteristic wavelength passing through an

atomic vapor layer of the element.

Used to measure concentration of trace metals

that are not easily excited (trace metals)


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Principle:Atoms are excited at higher orbital by absorbing

a set of quantity energy. The excited atoms then

return to the ground state, emitting light of the

same energy as it is absorbed

The amount of light emitted is distinguished and

measured


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Parts

Hollow-Cathode Lamp = radiation source;

contains a cylindrical cathode, inert gases (He &

Ar)

Flame Burner = reduces sample/metal being

determined from an ion/molecule to a neutral

atomic state

Monochromator = isolate the desired emitted

light


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PMTube = detects isolated emitted light

Readout System = for the display of

results

Light Chopper = light detector that

distinguishes light between that emitted by

the lamp and that emitted by the excited

atoms


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it blocks the light from the lamp,

so the detector measures only

the light emitted by the atoms in

the flame


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As the light chopper turns, it will move into a

position where it does not block the light from

the lamp, so the detector measures both the

light emitted by the atoms in the flame and

the lamp light that is not absorbed by the

atoms in the flame. This allows the AAS

instrument to account for the light emitted by

the atoms in the flame.


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AtomicAbsorption

Spectrophotometry


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New Trends

Use ofinductively coupled plasma = results to

increased sensitivity ofAA spectrophotometer

ICP = provides a torch of argon plasma

Argon Plasma + Argon Gas 5500 - 8000 K

Resulting to complete atomization of elements


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FlameAtomicAbsorption

Spectrophotometry

A method used to determine the intensity

of radiations of various wavelengths in a

spectrum emitted by a chemical inserted

into a flame.


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Flame Photometry

Used to determine concentrations of alkali

metals Na, K orLi.

used to measure the element lithium in

serum or plasma in order to determine the

correct dosage of lithium carbonate, a

drug used to treat certain mental

disturbances, such as manic-depressive

illness (bipolar disorder)


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Principle:

The technique requires a liquid sample to be

aspirated, aerosolized, and mixed with

combustible gases, such as acetylene and air oracetylene and nitrous oxide. The mixture is

ignited in a flame whose temperature ranges

from 2100 to 2800 C.


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During combustion, atoms of the element

of interest in the sample are reduced to

free, unexcited ground state atoms, whichabsorb light at characteristic wavelengths.


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Steps

1. Sample is converted to an atomic vapor by a

flame

2. Thermal energy of the flame excites electrons

3. As excited atoms fall back to ground state, they

emit light at wavelengths characteristic of the

element

4. Intensity of light emission directly proportionalto the concentration of element being

measured


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Parts

Gas Supply = for the flame

AtomizerBurners = converts liquid sample

into vapor

Monochromator = isolates desired

wavelength

Detector = detects isolated light


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If the sample concentration is too high to

permit accurate analysis in linearity responserange, there are three alternatives that may help

bring the absorbance into the optimum working

range:

1) sample dilution2) using an alternative wavelength having a

lower absorptivity

3) reducing the path length by rotating the

burner hand.

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