OTHER TYPES SPECTROPHOTOMETRY Flashcards

1
Q

OTHER TYPES SPECTROPHOTOMETRY

A

● Double beam spectrophotometry

● Flame emission spectrophotometry

● Atomic absorption spectrophotometry

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2
Q

● Light is directed forward in two directions by a rotating chopper.

A

DOUBLE BEAM SPECTROPHOTOMETRY

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3
Q

One light path is directed forward the_____ cuvette, while, simultaneously the other is directed towards the_____ cuvette

A

DOUBLE BEAM SPECTROPHOTOMETRY

sample

reference

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4
Q

● The intensity of the two light beams is then measured by one or two photodetectors.

● The sample beam is then compared to that of the reference beam

A

Double beam spectrophotometer

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5
Q

TWO FUNDAMENTAL INSTRUMENT DESIGNS of Double Beam Spectrophotometer

A

Double Beam in Space

Double Beam in Time

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6
Q

uses two photo detectors (one for the sample and one for the reference beam)

sample and reference are measured simultaneously and the signal from the reference is subtracted from the transmittance of light of the sample

A

Double Beam in Space

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7
Q

one photo detector and alternately passes the monochromatic radiation through the sample cuvette to the reference cuvette using a chopper

each beam consisting of a pulse of radiation breaks up separated in time by a dark interval

A

Double Beam in Time

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8
Q

■ device consist of circular disk

■ is a rotating sector of mirror that breaks up or rotates radiation beams

A

Chopper

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9
Q

Chopper

⅓ of the disk is_____;
⅓ is________ and the remaining
⅓ is______

A

opaque

transparent

mirrored

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10
Q

Splits the monochromatic beam of light into 2 beams of equal intensities

A

Chopper

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11
Q

measures Group 1 Metals that contains plus 1 in charge

A

FLAME EMISSION SPECTROPHOTOMETRY

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12
Q

Principle: “Involves measurement of electromagnetic radiation emitted by the excited atoms in the flame”

measures light emitted by excited atoms

A

FLAME EMISSION SPECTROPHOTOMETRY

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13
Q

The measurement of emitted light when electrons in an atom become excited by heat energy produced by the flame and returns to ground state.

A

Flame emission spectrophotometry

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14
Q

are no longer routinely used in clinical chemistry due to the development of iron selective electrodes ( Sodium, Potassium and Lithium)

A

Flame Photometers

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15
Q

Components of flame emission spectrophotometry

A

Atomizer
Flame

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16
Q

¡ breaks up the solution into finer droplets so that the atom will absorb heat energy from the flame and get excited

A

Atomizer

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17
Q

convert the analyte of the liquid sample into vapour state (breaks the chemical bonds to produce atoms)

source of energy that will be absorbed by the atoms to enter the excitation state

A

Flame

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18
Q

Types of burners

A

Total consumption burners

Premix burner

19
Q

§ the sample is aspirated directly into the flame. All the sample that enters the capillary will enter the flame regardless of the droplet size

A

Total consumption burners

20
Q

ADVANTAGE:
▪ Design is simple and entire sample is consumed

DISADVANTAGE:
▪ Uniform and homogeneous flame is not obtained
▪ Droplet size vary, leading to fluctuations in the flame intensity

A

Total consumption burners

21
Q

§ aspirated sample, fuel and oxidant are thoroughly mixed before reaching the burner opening and then entering the flame

A

Premix burner

22
Q

Only a small portion (about 5%) of the sample reaches the flame in the form of small droplets and is easily decompose.

A

Premix burner

23
Q

▪________ is non-turbulent, noiseless and stable.
▪ Easy decomposition which leads to high atomization

A

Premix burner

24
Q

Flames in flame emission

Potassium K

A

Violet

25
Q

Flames in flame emission

Lithium Li

A

Red

26
Q

Flames in flame emission

Calcium Ca

A

Orange

27
Q

Flames in flame emission

Sodium Na

A

Yellow

28
Q

Flames in flame emission

Barium Ba

A

Lime green

29
Q

INTERFERENCE FILTER

■ Transmits only yellow light (589 nm)

A

○ Na filter

30
Q

INTERFERENCE FILTER

■ Transmits only violet light (367 nm)

A

K filter

31
Q

INTERFERENCE FILTER

■ Transmits only red light (767 nm)

A

Lithium

32
Q

● Group two metals

● 2 (+) charges

● NOT EASILY EXCITED but can ABSORB light!!!

A

ATOMIC ABSORPTION SPECTROPHOTOMETRY

33
Q

Principle ○ Measures concentration of element by detecting absorption of electromagnetic radiation by atoms

It is sensitive and precise and routinely used to measure concentration of Trace metals that are not easily exciting.

A

ATOMIC ABSORPTION SPECTROPHOTOMETRY

34
Q

Atomic absorption spectrophotometry

The elements are not excited but they are dissociated from their chemical bonds and placed in the_______, _______

A

unionized, unexcited ground state

35
Q

Atomic absorption spectrophotometry

Components (6)

A

Light source
Mechanical rotating chopper
Burner
Monochromator
Detector
Read-out device

36
Q

Atomic absorption spectrophotometry

Light Source :

A

hollow cathode lamp

37
Q

AAS

modulates light beam coming from the light source

A

Mechanical Rotating Chopper

38
Q

AAS

Uses flame to dissociate the chemical bonds and form free unexcited atoms

A

Burner

39
Q

AAS

selects the desired wavelength from a spectrum of wavelength

A

Monochromator

40
Q

○ It measures the radiation emitted by the excited atoms that is related to concentration

A

Flame Emission

41
Q

○ It measures the radiation absorbed by the unexcited atoms that are determined

A

Atomic Absorption

42
Q

depends only upon the number of unexcited atoms, the absorption intensity is not directly affected by the temperature of the flame.

A

Atomic absorption

43
Q

in contrast being dependent upon the number of excited atoms, is greatly influenced by temperature variations.

A

flame emission intensity

44
Q

ATOMIC ABSORPTION SPECTROPHOTOMETRY

● Interferences:

■ _________ - Situation at which the flame could not dissociate the sample into neutral atoms

■ _________ - Situation at which atoms in the flame become excited and emits energy

A

Chemical

Ionization