OTHER TYPES SPECTROPHOTOMETRY

Question 1

OTHER TYPES SPECTROPHOTOMETRY

Answer 1

● Double beam spectrophotometry

● Flame emission spectrophotometry

● Atomic absorption spectrophotometry

Question 2

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

Answer 2

DOUBLE BEAM SPECTROPHOTOMETRY

Question 3

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

Answer 3

DOUBLE BEAM SPECTROPHOTOMETRY

sample

reference

Question 4

● 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

Answer 4

Double beam spectrophotometer

Question 5

TWO FUNDAMENTAL INSTRUMENT DESIGNS of Double Beam Spectrophotometer

Answer 5

Double Beam in Space

Double Beam in Time

Question 6

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

Answer 6

Double Beam in Space

Question 7

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

Answer 7

Double Beam in Time

Question 8

■ device consist of circular disk

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

Answer 8

Chopper

Question 9

Chopper

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

Answer 9

opaque

transparent

mirrored

Question 10

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

Answer 10

Chopper

Question 11

measures Group 1 Metals that contains plus 1 in charge

Answer 11

FLAME EMISSION SPECTROPHOTOMETRY

Question 12

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

measures light emitted by excited atoms

Answer 12

FLAME EMISSION SPECTROPHOTOMETRY

Question 13

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

Answer 13

Flame emission spectrophotometry

Question 14

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

Answer 14

Flame Photometers

Question 15

Components of flame emission spectrophotometry

Answer 15

Atomizer
Flame

Question 16

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

Answer 16

Atomizer

Question 17

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

Answer 17

Flame

Question 18

Types of burners

Answer 18

Total consumption burners

Premix burner

Question 19

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

Answer 19

Total consumption burners

Question 20

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

Answer 20

Total consumption burners

Question 21

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

Answer 21

Premix burner

Question 22

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

Answer 22

Premix burner

Question 23

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

Answer 23

Premix burner

Question 24

Flames in flame emission

Potassium K

Answer 24

Violet

Question 25

Flames in flame emission Lithium Li

Answer 25

Red

Question 26

Flames in flame emission Calcium Ca

Answer 26

Orange

Question 27

Flames in flame emission Sodium Na

Answer 27

Yellow

Question 28

Flames in flame emission Barium Ba

Answer 28

Lime green

Question 29

INTERFERENCE FILTER ■ Transmits only yellow light (589 nm)

Answer 29

○ Na filter

Question 30

INTERFERENCE FILTER ■ Transmits only violet light (367 nm)

Answer 30

K filter

Question 31

INTERFERENCE FILTER ■ Transmits only red light (767 nm)

Answer 31

Lithium

Question 32

● Group two metals ● 2 (+) charges ● NOT EASILY EXCITED but can ABSORB light!!!

Answer 32

ATOMIC ABSORPTION SPECTROPHOTOMETRY

Question 33

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.

Answer 33

ATOMIC ABSORPTION SPECTROPHOTOMETRY

Question 34

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

Answer 34

unionized, unexcited ground state

Question 35

Atomic absorption spectrophotometry Components (6)

Answer 35

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

Question 36

Atomic absorption spectrophotometry Light Source :

Answer 36

hollow cathode lamp

Question 37

AAS modulates light beam coming from the light source

Answer 37

Mechanical Rotating Chopper

Question 38

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

Answer 38

Burner

Question 39

AAS selects the desired wavelength from a spectrum of wavelength

Answer 39

Monochromator

Question 40

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

Answer 40

Flame Emission

Question 41

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

Answer 41

Atomic Absorption

Question 42

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

Answer 42

Atomic absorption

Question 43

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

Answer 43

flame emission intensity

Question 44

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

Answer 44

Chemical Ionization