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Quality Control > Atomic Absorption Spectroscopy (AAS) > Flashcards

Atomic Absorption Spectroscopy (AAS) Flashcards

1
Q

what is an atom made up of?

A

Of a nucleus surrounded by electrons

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2
Q

What is the ground state in the normal orbital configuration for an atom?

A

it is the lowest energy, most stable electronic configuration of an atom

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3
Q

What happend if the energy of the right amgnitude is applied to an atom?

A

The energy will be absorbed by the atom, and an outer electron will be promoted to a less stable configuration

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4
Q

what’s the name of the less stable configuration state?

A

it is the excited state

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5
Q

What happend to the atom at the excited state?

A

the atom will immediately and spontaneously return to its ground state configuration

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6
Q

What’s the results of the return of the atome to its ground state?

A

the energy intially absorbed in the excitation process will be emitted.

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7
Q

What’s the different between excitation and decay?

Draw the difference

A

the excitation is forced by suppying energy, whereby the decay proces involve the emission of light, occurs spontaneously

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8
Q

how is the wavelength related to the electronic transition?

A

the wavelength of the emitted radiant energy is directly related to the eletronic transition

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9
Q

AA emission is?

A

On measured the emitted light at the wavelength of the elment to be determined

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10
Q

How is the emission intensity correlated to the number of atoms?

A

the intensity at the wavelength will be grater as the number of atoms of the analyte element increase

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11
Q

Define atomic absorbtion

A

When the right wavelength impinges on a free, ground state atom, the atom aborb the light at it enters an excited state

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12
Q

What’s the relation between the quantity of interest and the amount of light absorbed?

A

the quantity of interest is the amount of light which is absorbed as the light passes through a cloud of atoms.

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13
Q

Describe the atomic absorption process

A
  1. A light (resonance wavelength) of intialy intensity (Io) is forced on th e flame cell containing ground state atoms.
  2. the detector measred the reduced light intensity (I)
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14
Q

How does the intial light intensity decreases?

A

it decrease by an amount determined by the atom concentration in the flame cell

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15
Q

Define transmittance (T)

A

it is the ratio of the final intensity to the inital intensity (T= I/Io)

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16
Q

What’s the percent transmission

A

%T= 100* I/Io

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17
Q

relation between the percent absorption and percent transmission

A

the percent absorption is the complemnt of percent transmission
%A= 100- %T

18
Q

How is the absorbance define absorbance

A

A= log(Io/I)

19
Q

what is the absorbance?

A

it is the used for characterzing light absorption in AAS

20
Q

Why do we used the absorbance?

A

it’s floows a linear relationship with concentration

21
Q

Formal for the Beer’s law

A

A=abc
a: absortion coefficient
b: length
C: concentration

22
Q

What’s the meaning of Beer’s law equation?

A

it’s tells us that the absornace is diretly proportional to the concentration of the absorbing species.

23
Q

What are the component of an AAS?

Draw it

A

light soure, sample cell, specific light measurement (Monochromator, detector, electronics and readout)

24
Q

What’s the widely used light source

A

Hollow cathode lamp

Electrodeless discharge lamp

25
Q

What’s the used of a monochromator?

A

it is used to disperse the varous wavelengths of light which are emitted from the source and to isolte the particular line (wavelength) of interest

26
Q

why is a narrow light absortion important?

A

it is of importance to use a line source which emits the specific wavelngths which can be absorbed by the atom.
Narrow line sources provide high sensitivity

27
Q

Describe the process of an AAS

1.Process

A

The element of interest is dissolve in a solvent.
The liquid is drawn into the nebulizer and mixed with oxidanet (air) and fule (acetylene), where it gets disperes into small droplets (Aerosol)
Aerosol enters in the flame, where the liquid is evaporated

28
Q

Describe the process of an AAS

2 .Process

A

Aerosol enters in the flame, where the liquid is evaporated, remaining solid is vaporized

29
Q

Describe the process of an AAS

3 .Process

A

the solid sampe is decomposed into atoms

30
Q

What the flams temperature and by what it is created?

A

it is created by the air-acetylene, 2400-2700 K

31
Q

Describe the process in the HCL

A

the applied voltage in the HCL ionizes the gas which fills the lamp
positive ions are accelarated toward the cathode.the catiosn strike the cathode, creating energy which takes the matal atoms frin the cathode into the gas phase. Due to collisions in the gase ohase, the atoms are excited of the specific elemnt which emit high-energy protons with the frequency that the analyte inside the flame needs to absorb

32
Q

Why do we need to used a specific light source and not a normal light?

A

According to the Beer’s law is it important to have a line relation between the absorbtion and the concentration of the element.
the atom can only absorbt a tiny fraction of all of the light of the monochromater, producing a very non-linar response.

33
Q

What is important in the HCL

A

in the HCL, the lamp content the same element a that which is to be determined. Therefore, the wevelength emission profile gives the same engery and shape as the atom in the sample. Therefore, on can directly match the wavelength from the light as beig absorbt by the sample

34
Q

What’S the main different between atoms and molecules

A

Atoms can only aborbt energy, but they can’t rotate or vibrat to gain energy. Therefore, atom have a very narrow absorption lines

35
Q

What’s the disadvantage of this method?

A

one needs a different lamp for each type of metal which is to be determined

36
Q

what is important in the atoms to get in th excited state?

A

they need to absorbt radiation in the same frequency of their energetic level between the ground and the excited state

37
Q

Importance of Ascorbic acid and the reaction

A

it is an antioxidant, which reduces Fe(3+) to Fe(2+) in the human body

38
Q

Why is the lambert-beer law limited in the AAS

A

it is due to the thickness of the flame, which cannot be dtermined exactly

39
Q

What is ppm

A

ppm means part per million which is equal to mg/l

40
Q

Why do we used ppm instead of the %

what is the visualization of the ppm?

A

the numerical value will be extremely samll in a number of decimal places if the % is used
one inch in 16 miles

41
Q

what is the results of a prologe exposure of zinc in the body?

A

it can reduce immune function and lower the high density of lipoprotein (HDL)

42
Q

What is a Milli-Q water

A

it is an ultrapure water, deionized through the filter to remove particles. it is more pure than distilled water

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