This set of Analytical Instrumentation Multiple Choice Questions & Answers (MCQs) focuses on “Detection System of Liquid Chromatography”.
1. In liquid scintillation counter, which of the following is a fluorescent substance?
a) Solvent
b) Solute
c) Crystal
d) Reagent
View Answer
Explanation: In liquid scintillation counter, a mixture of solvent and solute is used. The solute is a fluorescent substance.
2. When UV light is absorbed by the fluor molecules the light emitted is in which of the following colours?
a) Pink
b) Red
c) Green
d) Blue
View Answer
Explanation: When UV light is absorbed by the fluor molecules the light emitted is in blue colour. Light is emitted when the molecules return to the ground state.
3. In liquid scintillation counter, which of the following is used to convert light into electrical signals?
a) Photo multiplier tube
b) Photo emissive tube
c) Photo voltaic cell
d) Photo reflector
View Answer
Explanation: The photo multiplier tube converts light into electrical signals in a liquid scintillation counter. Two photo multiplier tubes are used in the liquid scintillation counter.
4. The reduction in counting efficiency of the scintillation detector is called as __________
a) Disintegration
b) Decay
c) Quenching
d) Reduction
View Answer
Explanation: The reduction in counting efficiency of the scintillation detector is called as quenching. Substances added to the counting vial can reduce efficiency.
5. Which of the following is not a type of quenching?
a) Chemical quench
b) Interference quench
c) Colour quenching
d) Self-absorption
View Answer
Explanation: There are three types of quenching. Interference quench is not a type of quenching.
6. In which type of quenching, the radiation emitted by the isotope is not detected due to absorption of the radiation by the sample itself?
a) Chemical quench
b) Interference quench
c) Colour quenching
d) Self-absorption
View Answer
Explanation: In self-absorption, the radiation emitted by the isotope is not detected due to the absorption of the radiation by the sample itself. It may occur due to precipitates.
7. Variation of gain with temperature does not cause instability.
a) True
b) False
View Answer
Explanation: Variation of gain with temperature causes instability. There are various other factors that cause instability.
8. Due to the presence of red, green and yellow colour in the vial, which of the following occurs?
a) Chemical quench
b) Interference quench
c) Colour quenching
d) Self-absorption
View Answer
Explanation: Scintillators emit light in the blue region of the spectrum. Due to the presence of other colours, colour quenching may occur.
9. A quench curve can be constructed by plotting the counting efficiency versus ____________
a) Q-number
b) Quench factor
c) H-number
d) Disintegrations
View Answer
Explanation: A quench curve can be constructed by plotting the counting efficiency versus H-number. This is done using a set of samples with known activity.
10. Photomultipliers used in Liquid scintillation detectors are a source of instability.
a) True
b) False
View Answer
Explanation: Photomultipliers used in Liquid scintillation detectors are a source of instability. Various factors cause instability.
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