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Clinical Chemistry > Module 3b: Luminiscence > Flashcards

Module 3b: Luminiscence Flashcards

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1
Q

Define luminiscence

A

any emission of light when an electron returns from an excited state (by any other energy other than heat) to ground state

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2
Q

There are four types of luminiscence which are

A
  1. fluorescence
  2. phosphorescence
  3. chemiluminiscemce
  4. electrochemiluminiscence
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3
Q

Luminiscence should be observed at what direction and why?

A

Perpendicular to the incident light to avoid detection of scattered radiation

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4
Q

In quantitative analysis, the intensity of luminiscence is proportional to

A

concentration of species (C)
incident radiant power (P0)
constant depending on emitting molecule (k)

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5
Q

An atom or molecule that can fluoresce

A

fluorophore

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6
Q

Makes Fluorescence measurements 100 to 1000 times more sensitive than absorbance measurements

A
  1. intense light source
  2. digital signal filtering
  3. sensitive emission photometers
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7
Q

Principle of Fluorometry

A

Molecule that has greater energy that the environment fluoresces where returning to ground state.

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8
Q

Test based on the principle of fluorescence

A

Fluorometry

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9
Q

Components of fluorometers

A
  1. light source (excitation source)
  2. excitation or primary monochromator (larger than absirbance spectrophotometers)
  3. sample cell
  4. emission or secondary monochromator
  5. detector
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10
Q

Difference between fluorometer and spectrofluormeter

A

Fluorometer - uses interference or glass filters

Spectrofluorometer - prism or grating monochromator

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11
Q

Application of Fluorometry

A
  • fluorescent tags or labels
  • hematofluorometry of zinc protoporphyrin in whole blood
  • flow cytometry
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12
Q

Concentration effect that refers to the loss of excitation intensity across the cuvet path length as the fluorophor absorbs the excitation light

A

Inner filter effect

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13
Q

Concentration effect where a macromolecule, like an antibody, is labeled heavily with a fluorophor, and radiationless energy transfer occurs.

A

concentration quenching

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14
Q

The difference between excitation light and emitted fluorescence in fluorometry

A

Stoke’s Shift

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15
Q

When the excitation and emission spectra overlap in fluorescence.

A

Light Scattering

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16
Q

Limitation of fluorometer in which a serum or urine sample contain many compounds that fluoresce which contributes to unwanted background fluorescence.

A

sample matrix effects

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17
Q

The most serious contributors to sample matrix effect in fluorometry

A

proteins and bilirubin

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18
Q

The temperature in fluorometry must be regulated within

A

+/- 0.1 °C

19
Q

Fluorescence intensity ________ with increasing temperature by approximately

A

decreases

1-5 percent per degree Celsius

20
Q

Limitation of fluorrometry where weakly fluorescing or dilute solution are affected by intense light sources

A

photodecomposition

21
Q

Six limitation of Fluorometry

A
  1. concentration effects
  2. Light scattering
  3. solvent and cuvette effects
  4. sample matrix effects
  5. temperature effects
  6. photodecomposition
22
Q

Test that is similar to flurometry but is distinguished in that it continues to occur even
after the radiation causing it has ceased.

A

Phosphorescence

23
Q

Difference between the emitted light in Fluoremetry amd Phossphorescence

A

There is a larger shift in wavelength in phosphorescence

24
Q

Types of luminescence in which the excitation event is caused by a chemical or electrochemical reaction, not by photolumination

A

Chemiluminiscemce and bioluminiscence

25
Q

Principle of chemiluminiscence

A

Compounds react with an oxidizing agent, with a catalyst,
It shifts into excited state.
Light is emitted as the product returns to ground state.

26
Q

Common substrates in chemiluminiscence

A

luminol
isoluminol
acridinium estees
luciferin

27
Q

Common oxidants in chemiluminiscence

A

hydrogen peroxide
hypochlorite
oxygen

28
Q

Commonly used catalysts in Chemiluminiscence

A 
enzymes (alkaline phospahatase, horseradish peroxidase, microperoxidase)
metal ions (copper, ferric phthalocyanine complex)
29
Q

substrate, oxidizer, and catalyst used in forensics as diagnostic tool for the detection of blood and other biological fluids.

A

luminol, hydrogen peroxide, peroxidase

30
Q

A special form of chemiluminescence occurring within biological systems.

A

bioluminiscence

31
Q

Biological substrate, oxidizer and catalyst in fireflies

A

Luciferin, oxygen, luciferase

32
Q

another example of biological caatalysts in bioluminiscemce

A

aequorin

33
Q

Type of luminescence where the reactive species that produce the chemiluminescent reaction are electrochemically generated.

A

Electrochemiluminiscence

34
Q

Advantages of Electrochemiluminiscence

A

reagent stability
simple reagent prepartion
enhanced sensitivity

35
Q

A physical phenomenon resulting from the interaction of light with particles in solution.

A

Light scattering

36
Q

Difference between fluorometry and light scattering techniques

A

scattered light has smiliar frequency as incident light

37
Q

Best application of Light scattering techniques

A

Immunoassay of specific serum proteins and haptens

38
Q

Two types of light scattering techniques

A

turbidimetry

nepehlometry

39
Q

Measures the decrease in intensity of the incident light at 180 degrees from the incident beam

A

turbidimetry

40
Q

It is the detection of light energy that js scattered or reflected toward a detector that is not in the direct path of the transmitted light, usually measured at a right angle.

A

nepehelometry.

41
Q

What is measured in turbidimetry?

A

blocked light

42
Q

what is measured in nephelometry?

A

scattered light

43
Q

Nephelometry that is commonly used in measuring macromolecules with size larger than the wavelength of incident light.

A

Forward scattering nephelometer

Clinical Chemistry (14 decks)

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