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CC LEC > Luminescence > Flashcards

Luminescence Flashcards

1
Q

• is the emission of light by a substance

A

Luminescence

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2
Q

• occurs when an electron returns to the electronic ground state from an excited state and loses its excess energy as a photon

A

Luminescence

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3
Q

Three types of luminescence

A

• Fluorescence

• Phosphorescence

• Chemiluminescence

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4
Q

• It starts immediately after the absorption of light and stops as soon as the incident light is cut off

A

Fluorescence

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5
Q

• When a beam of light is incident on certain substances, they emit visible light or radiations

A

Fluorescence

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6
Q

• When light radiation is incident on certain substances, they emit light continuously even after the incident light is cut off.

A

Phosphorescence

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7
Q

• delayed fluorescence

A

Phosphorescence

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8
Q

• Measures the fluorescence or the energy emission that occurs when a certain compound absorb electromagnetic radiation, become excited and then return to an energy state that is usually higher than their original level

A

Fluorometry

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9
Q

Basic Components of a Fluorometry (5)

A

Light source
Excitation/ primary monochromator
Cuvette
Emission/ secondary monochromator
Photodetector

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10
Q

Advantages:

• Increased sensitivity (1000x more sensitive than________ methods)

• Emitted radiation is measured directly

• Increased specificity by selecting the optimal wavelength for both absorption and fluorescence

A

Fluorometry

spectrophotometric

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11
Q

Disadvantage:

• very sensitive to______ changes

•

A

Fluorometry

environmental

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12
Q
  • quick disappearance of fluorescence

• changes in____ affects electron availability

•_______ changes the probability of loss of energy

• contaminating chemicals or a change of______ may change the structure

• UV light used for excitation can cause______ changes

A

Quenching

pH

temperature

solvent

photochemical

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13
Q

• is the production of light from a chemical reaction

• reactions are oxidation reactions of (3) characterized by a rapid increase in intensity of emitted light followed by a gradual decay

A

Chemiluminescence

luminol, acridinium esters, and dioxetanes

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14
Q

• The excitation of the substance does not involve electromagnetic radiation and no monochromators are needed, instead the excitation energy comes from a chemical or electrochemical reaction

A

Chemiluminescence

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15
Q

• Light signal is measured against a completely dark background

A

Chemiluminescence

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16
Q

Advantages:

• Subpicomolar detection limits
• Speed
• Ease of use
• Simple instrumentation

A

Chemiluminescence

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17
Q

• Impurities can cause a background signal that degrades sensitivity and specificity

A

Chemiluminescence

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18
Q

is a physical phenomenon that results from the interaction of light with particles in solution

A

Light scattering

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19
Q

• Unlike fluorescence emission, the wavelength of the ________is the same as that of the incident light

A

scattered light

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20
Q

measures the amount of light scattered in a particulate suspension at 90º angle

A

Nephelometry

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21
Q

useful method to determine the concentration of solutions that contains particles too large for absorption spectrometry

A

Nephelometry

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22
Q

• Amount of light blocked depends not only on concentration but also on size

• Sampling handling becomes critical

A

Turbidimetry

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23
Q

• measures the amount of light blocked in a particulate suspension in light transmission

A

Turbidimetry

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24
Q

_______, the amount of light passing through a solution is measured.

A

Turbidimetry

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25
Q

The higher the turbidity, the_____ the quantity of light transmitted (i.e. more light is absorbed).

A

smaller

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26
Q

Any _______ can be used as a turbidimeter, without modification. Since property concerns visible light the measurement is commonly carried out at_____.

A

spectrophotometer or photometer

420 nm

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27
Q

he detecting cell is placed at right angles to the light source, to measure light scattered by particles.

A

nephelometry

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28
Q

The intensity of the scattered light serves as a measure of the turbidity. The instrument is called a ________

A_______, can be used, however, a special attachment is required for nephelometry.

A

‘Nephelometer’ or a ‘Nephelometric Turbidimeter’.

spectrophotometer

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29
Q

• Mercury arc lamp

• Scattered light is measured

• Measured at 90 degrees

• PMT is the detector

A

Nephelometry

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30
Q

• Tungsten lamp

• Light transmitted is measured

• Measured in straight line

• Photocell is the detector

A

Turbidimetry

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31
Q

Factors that affect scattered light

A

• Particle size

• Concentration of particles

• Molecular weight of particles

• Wavelength dependence

32
Q

Three Types of Scattered Light

A

• Rayleigh

• Mie

• Rayleigh Debye

33
Q

• Light symmetrically scattered around the particle

A

Rayleigh

34
Q

• Wavelength of light > particle size

A

Rayleigh

35
Q

• Light scatters backward but appears forward due to destruction out of phase background scatter

A

Mie

36
Q

• Wavelength of light < particle size

A

Mie

37
Q

• Antigen-antibody reactions

A

Rayleigh Debye

38
Q

• More forward light scatter

A

Rayleigh Debye

39
Q

• Wavelength of light = particle size

A

Rayleigh Debye

40
Q

Quick disappearance of fluorescence

A

Quenching

41
Q

Changes in ____ affects electron availability

A

pH

42
Q

______ changes the probability of loss energy

A

Temperature

43
Q

Contaminating chemical or change of ______ may change the structure

A

Solvent

44
Q

UV light used for excitation can cause ______ changes

A

Photochemical

45
Q

Chemiluminescence are from ______ reactions

A

Oxidation

46
Q

T or F

Fluorometry is more sensitive than spectrophotometry

A

TRUE

47
Q

Lamp used for nephelometry

A

Mercury arc lamp

48
Q

Detector of nephelometry

A

Photomultiplier

49
Q

What is measured in nephelometry

A

Scattered light

50
Q

Lamp used in Turbidimetry

A

Tungsten lamp

51
Q

What is measured in Turbidimetry

A

Light transmitted

52
Q

Detector of Turbidimetry

A

Photocell

53
Q

How many monochromator does a fluorometry have

A

2

54
Q

T or F

Fluorometry has only one monochromator

A

FALSE

55
Q

T or F

In fluorescence, the energy given off is less than that of absorbed

A

True

56
Q

T or F

In fluorescence, the wavelength of the light given off is usually longer than that of absorpbed

A

True

57
Q

Photodetector of Fluorometry

A

PMT

58
Q

Attenuater

A

Entrance slit

59
Q

Molecule that fluoreces

A

Fluorophore

60
Q

Angle of secondary monochromator in Fluorometry

A

Right angle or 90* angle

61
Q

Substances that can absorb light/cause fluorescence:

● Impurities can cause a background signal that degrades sensitivity and specificity

A

● POPOP = phenyloxazole benzene
● Quinine
● Fluorescein
● Acridine orange
● Rhodamine B
● Pyridine 1

62
Q

T or F

Fluorometry has increased sensitivity 1000x more sensitive than the spectrophotometric methods

A

True

63
Q

Emitted radiation is measured directly

A

Fluorometry

64
Q

increases specificity by selecting the optimal wavelength for both absorption and fluorescence

A

Fluorometry

65
Q

characterized by a rapid increase in intensity of emitted light followed by a gradual decay

A

Chemiluminescence

66
Q

Subpicomolar detection limits

A

Chemiluminescence p

67
Q

Measures light scattering

A

Nephelometry and Turbidimetry

68
Q

Lamp of nephelometry

A

Mercury arc

69
Q

Lamp of Turbidimetry

A

Tungsten

70
Q

Nephelometry measures

A

Scattered light

71
Q

Turbidimetry measures

A

Light transmitted

72
Q

Nephelometry is measured in what angle

A

90*

73
Q

Turbidimetry is measured in what angle

A

Straight line

74
Q

Detector of nephelometry

A

PMT

75
Q

Detector of Turbidimetry

A

Photocell

CC LEC (39 decks)

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