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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
The higher the turbidity, the_____ the quantity of light transmitted (i.e. more light is absorbed).
smaller
26
Any _______ can be used as a turbidimeter, without modification. Since property concerns visible light the measurement is commonly carried out at_____.
spectrophotometer or photometer 420 nm
27
he detecting cell is placed at right angles to the light source, to measure light scattered by particles.
nephelometry
28
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.
'Nephelometer' or a 'Nephelometric Turbidimeter'. spectrophotometer
29
• Mercury arc lamp • Scattered light is measured • Measured at 90 degrees • PMT is the detector
Nephelometry
30
• Tungsten lamp • Light transmitted is measured • Measured in straight line • Photocell is the detector
Turbidimetry
31
Factors that affect scattered light
• Particle size • Concentration of particles • Molecular weight of particles • Wavelength dependence
32
Three Types of Scattered Light
• Rayleigh • Mie • Rayleigh Debye
33
• Light symmetrically scattered around the particle
Rayleigh
34
• Wavelength of light > particle size
Rayleigh
35
• Light scatters backward but appears forward due to destruction out of phase background scatter
Mie
36
• Wavelength of light < particle size
Mie
37
• Antigen-antibody reactions
Rayleigh Debye
38
• More forward light scatter
Rayleigh Debye
39
• Wavelength of light = particle size
Rayleigh Debye
40
Quick disappearance of fluorescence
Quenching
41
Changes in ____ affects electron availability
pH
42
______ changes the probability of loss energy
Temperature
43
Contaminating chemical or change of ______ may change the structure
Solvent
44
UV light used for excitation can cause ______ changes
Photochemical
45
Chemiluminescence are from ______ reactions
Oxidation
46
T or F Fluorometry is more sensitive than spectrophotometry
TRUE
47
Lamp used for nephelometry
Mercury arc lamp
48
Detector of nephelometry
Photomultiplier
49
What is measured in nephelometry
Scattered light
50
Lamp used in Turbidimetry
Tungsten lamp
51
What is measured in Turbidimetry
Light transmitted
52
Detector of Turbidimetry
Photocell
53
How many monochromator does a fluorometry have
2
54
T or F Fluorometry has only one monochromator
FALSE
55
T or F In fluorescence, the energy given off is less than that of absorbed
True
56
T or F In fluorescence, the wavelength of the light given off is usually longer than that of absorpbed
True
57
Photodetector of Fluorometry
PMT
58
Attenuater
Entrance slit
59
Molecule that fluoreces
Fluorophore
60
Angle of secondary monochromator in Fluorometry
Right angle or 90* angle
61
Substances that can absorb light/cause fluorescence: ● Impurities can cause a background signal that degrades sensitivity and specificity
● POPOP = phenyloxazole benzene ● Quinine ● Fluorescein ● Acridine orange ● Rhodamine B ● Pyridine 1
62
T or F Fluorometry has increased sensitivity 1000x more sensitive than the spectrophotometric methods
True
63
Emitted radiation is measured directly
Fluorometry
64
increases specificity by selecting the optimal wavelength for both absorption and fluorescence
Fluorometry
65
characterized by a rapid increase in intensity of emitted light followed by a gradual decay
Chemiluminescence
66
Subpicomolar detection limits
Chemiluminescence p
67
Measures light scattering
Nephelometry and Turbidimetry
68
Lamp of nephelometry
Mercury arc
69
Lamp of Turbidimetry
Tungsten
70
Nephelometry measures
Scattered light
71
Turbidimetry measures
Light transmitted
72
Nephelometry is measured in what angle
90*
73
Turbidimetry is measured in what angle
Straight line
74
Detector of nephelometry
PMT
75
Detector of Turbidimetry
Photocell

CC LEC (38 decks)

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