Chromatography Principles

What is the purpose of column efficiency in gas chromatography?

• Column efficiency in gas chromatography has no impact on the separation of compounds.

• Column efficiency in gas chromatography is essential for separating compounds effectively based on their chemical properties.

• Column efficiency in gas chromatography is used to measure the temperature of the column.

• Column efficiency in gas chromatography is only important for separating compounds based on their color.

Answer explanation

Column efficiency in gas chromatography is essential for separating compounds effectively based on their chemical properties.

What is the role of the mobile phase in HPLC?

• The mobile phase carries the sample through the stationary phase for separation.

• The mobile phase interacts with the detector

• The mobile phase analyzes the sample components

• The mobile phase determines the column temperature

How is retention time defined in gas chromatography?

• Retention time is defined as the time it takes for a compound to travel through the chromatography column and reach the detector.

• Retention time is the time it takes for a compound to change color in the column

• Retention time is the time it takes for a compound to dissolve in the column

• Retention time is the time it takes for a compound to evaporate in the column

Name two types of detectors used in HPLC.

• Mass spectrometry detectors

• Conductivity detectors

• Fluorescence detectors

• UV-Visible detectors, Refractive Index detectors

What is the function of the stationary phase in gas chromatography?

• Detecting the sample components

• Heating the sample

• Reducing the pressure

• Separating the components of the sample based on their interactions with the stationary phase.

Explain the concept of gradient elution in HPLC.

• Gradient elution in HPLC involves changing the composition of the mobile phase during the chromatographic run by gradually increasing the concentration of a stronger solvent while decreasing the concentration of a weaker solvent.

• Gradient elution requires decreasing the concentration of a stronger solvent while increasing the concentration of a weaker solvent.

• Gradient elution is a stationary phase used in HPLC.

• Gradient elution involves using a single solvent throughout the chromatographic run.

Answer explanation

Gradient elution in HPLC involves changing the composition of the mobile phase during the chromatographic run by gradually increasing the concentration of a stronger solvent while decreasing the concentration of a weaker solvent.

How does column efficiency affect the resolution in gas chromatography?

• Column efficiency affects the speed of analysis, not resolution in gas chromatography

• Column efficiency affects resolution in gas chromatography by enabling better separation of compounds based on their retention times.

• Column efficiency decreases resolution in gas chromatography

• Column efficiency has no impact on resolution in gas chromatography

Discuss the importance of selecting the appropriate mobile phase in HPLC.

• The mobile phase has no impact on the separation process

• Any random solvent can be used as a mobile phase

• The importance of selecting the appropriate mobile phase in HPLC lies in its compatibility with the stationary phase, solubility for the sample, and suitability for the compounds being analyzed.

• The mobile phase should be selected based on its color

Why is retention time a crucial parameter in gas chromatography?

• Retention time measures the temperature of the gas in the column

• Retention time determines the flow rate of the carrier gas

• Retention time is used to calculate the sample volume injected

• Retention time helps in identifying and separating different compounds in a sample.

Compare and contrast isocratic and gradient elution in HPLC.

• Isocratic elution involves changing the mobile phase composition over time.

• Gradient elution uses a constant mobile phase composition.

• Isocratic elution uses a constant mobile phase composition, while gradient elution involves changing the mobile phase composition over time.

• Isocratic elution is more time-consuming than gradient elution.