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Question 1:

What is the main principle behind gas chromatography?

A) Separation based on size
B) Separation based on charge
C) Separation based on molecular weight
D) Separation based on partitioning between stationary and mobile phases

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Explanation: The correct answer is D) Separation based on partitioning between stationary and mobile phases. The main principle behind gas chromatography is the separation of components of a mixture based on their partitioning between a stationary phase (often a liquid coating on a solid support) and a mobile phase (inert gas). The components interact differently with the stationary and mobile phases, leading to their separation.

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Question 2:

What is the stationary phase in gas chromatography?

A) Liquid coating on a solid support
B) Inert gas
C) Capillary column
D) Detector

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Explanation: The correct answer is A) Liquid coating on a solid support. In gas chromatography, the stationary phase is typically a liquid coating on a solid support. This stationary phase provides selectivity for separating components based on their chemical properties. Different types of stationary phases can be used, such as polar or non-polar coatings, depending on the analytes of interest.

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Question 3:

Which component is responsible for carrying the analytes through the column in gas chromatography?

A) Stationary phase
B) Mobile phase
C) Injection port
D) Detector

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Explanation: The correct answer is B) Mobile phase. In gas chromatography, the mobile phase is responsible for carrying the analytes through the column. The mobile phase is typically an inert gas, such as helium or nitrogen. It carries the analytes from the injection port through the column and towards the detector, facilitating their separation based on their interaction with the stationary phase.

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Question 4:

What is the purpose of the detector in gas chromatography?

A) Separating the analytes based on their molecular weight
B) Measuring the retention time of analytes
C) Providing electrical conductivity
D) Detecting and measuring the analytes

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Explanation: The correct answer is D) Detecting and measuring the analytes. The detector in gas chromatography is responsible for detecting and measuring the analytes as they elute from the column. It detects the presence and quantity of analytes based on their chemical or physical properties. Common types of detectors used in gas chromatography include flame ionization detectors (FID), thermal conductivity detectors (TCD), and mass spectrometry detectors (MS).

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Question 5:

What does the retention time represent in gas chromatography?

A) The time it takes for the analyte to reach the detector
B) The time it takes for the analyte to be injected
C) The time it takes for the analyte to interact with the stationary phase
D) The time it takes for the analyte to dissolve in the mobile phase

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Explanation: The correct answer is C) The time it takes for the analyte to interact with the stationary phase. Retention time in gas chromatography represents the time it takes for an analyte to interact with the stationary phase and travel through the column to reach the detector. It is a characteristic property of each analyte and can be used for identification and quantification purposes. The retention time depends on various factors, including the analyte's chemical properties and the column conditions.