Chromatography Methods Quiz Questions

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  • 1/18 Questions

    The weak mobile phase is a non-polar solvent (hexane, benzene) and the strong mobile phase is a polar solvent (water, methanol) is for polar supports

    • True
    • False
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About This Quiz

This quiz assesses knowledge on chromatography methods, focusing on the applicability of various chromatographic techniques to different substances. Key topics include Gas-Liquid, Liquid-adsorption, Gas-solid, and Ion exchange chromatography, enhancing understanding of their practical applications.

Chromatography Methods Quiz Questions - Quiz

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  • 2. 

    The weak mobile phase is a polar solvent and the strong mobile phase is a non-polar solvent for non-polar supports.

    • True

    • False

    Correct Answer
    A. True
    Explanation
    This statement is true because in chromatography, the mobile phase refers to the solvent that carries the sample through the stationary phase. In order to separate non-polar compounds, a polar mobile phase is used, while a non-polar mobile phase is used to separate polar compounds. This is because like dissolves like, meaning polar solvents will interact more strongly with polar compounds and non-polar solvents will interact more strongly with non-polar compounds. Therefore, a weak mobile phase that is polar and a strong mobile phase that is non-polar would be suitable for separating non-polar compounds.

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  • 3. 

    Changing the composition of the mobile phase with time aka solvent programming:

    Correct Answer
    gradient elution
    Explanation
    Gradient elution refers to a technique in liquid chromatography where the composition of the mobile phase is changed over time. This is also known as solvent programming. In gradient elution, a solvent gradient is created by increasing or decreasing the concentration of one or more components in the mobile phase. This allows for the separation of compounds with different polarities or affinities for the stationary phase. By gradually changing the composition of the mobile phase, gradient elution improves the resolution and efficiency of the chromatographic separation.

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  • 4. 

    Describe three general methods for improving resolution in partition chromatography.

    • Adjustment of kA and kB by employing a multicomponent mobile phase and varying the raiot of the solvents to find an optimal mixture.

    • Variation in the chemical composition of the solvent system in such a way as to make α larger.

    • Employing a different packing in which α is greater.

    • Going from a weak mobile phase to a strong one

    Correct Answer(s)
    A. Adjustment of kA and kB by employing a multicomponent mobile phase and varying the raiot of the solvents to find an optimal mixture.
    A. Variation in the chemical composition of the solvent system in such a way as to make α larger.
    A. Employing a different packing in which α is greater.
    Explanation
    The three general methods for improving resolution in partition chromatography are adjusting the kA and kB by employing a multicomponent mobile phase and varying the ratio of the solvents to find an optimal mixture, varying the chemical composition of the solvent system to make α larger, and employing a different packing in which α is greater. These methods aim to enhance the separation of components in the chromatographic system, either by manipulating the mobile phase or the stationary phase to achieve better resolution.

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  • 5. 

    List the types of substances to which each of the following chromatographic methods is most applicable:  Liquid- adsorption

    Correct Answer(s)
    Nonpolar low to moderate molecular mass organics and particularly isomeric organic species.
    Explanation
    The liquid-adsorption chromatographic method is most applicable to nonpolar low to moderate molecular mass organics, especially isomeric organic species. This is because the method involves the separation of compounds based on their affinity for the stationary phase, which in this case is a liquid. Nonpolar compounds with similar molecular masses and structures tend to have similar affinities for the stationary phase, making it easier to separate them using this method. Isomeric organic species, which have the same molecular formula but different arrangements of atoms, can also be effectively separated using liquid-adsorption chromatography.

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  • 6. 

    List the types of substances to which each of the following chromatographic methods is most applicable:     Gas- solid

    Correct Answer(s)
    Low molecular mass nonpolar gases.
    Explanation
    Gas-solid chromatography is most applicable to separate low molecular mass nonpolar gases. This is because in gas-solid chromatography, the stationary phase is a solid material, which interacts with the nonpolar molecules of the sample. The nonpolar gases will have stronger interactions with the stationary phase, leading to better separation and retention times. On the other hand, polar or high molecular mass gases may not interact as strongly with the stationary phase, resulting in poor separation and retention times.

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  • 7. 

    List the types of substances to which each of the following chromatographic methods is most applicable:   Ion exchange

    Correct Answer(s)
    Substances that are ionic or that can be derivatized to form ions.
    Explanation
    Ion exchange chromatography is most applicable to substances that are ionic or that can be derivatized to form ions. This is because ion exchange chromatography relies on the exchange of ions between the sample and the stationary phase. The stationary phase contains charged groups that attract and retain ions of opposite charge, allowing for the separation of different ionic species. Therefore, substances that are ionic or can be converted into ions are best suited for this chromatographic method.

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  • 8. 

    Isocratic elution

    Correct Answer(s)
    use of a constant mobile phase composition to elute solutes
    Explanation
    Isocratic elution refers to the technique of using a constant mobile phase composition to elute solutes in chromatography. In this method, the mobile phase composition remains unchanged throughout the separation process, allowing all solutes to be eluted at the same rate. This is in contrast to gradient elution, where the mobile phase composition is varied over time to achieve better separation of solutes. Isocratic elution is often used when the solutes have similar retention times and do not require a gradient to be effectively separated.

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  • 9. 

    In a stop-flow injection

    Correct Answer(s)
    the flow of solvent is stopped, a fitting at the head of the column is removed, and the sample is injected directly onto the head of the column. The fitting is then replaced and pumping is resumed.
  • 10. 

    A reversed-phase packing

    Correct Answer(s)
    is a nonpolar packing that is used in partition chromatography with a relatively polar mobile phase.
    Explanation
    A reversed-phase packing refers to a type of packing material used in partition chromatography. It is characterized by being nonpolar, meaning it does not have a charge or affinity for polar molecules. This type of packing is used in conjunction with a relatively polar mobile phase, which is the liquid or gas that carries the sample through the column. The nonpolar packing material and polar mobile phase create a reversed-phase system, allowing for the separation and analysis of polar compounds.

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  • 11. 

    In a normal-phase packing, 

    Correct Answer(s)
    the stationary phase is polar and the mobile phase is relatively nonpolar.
    Explanation
    In a normal-phase packing, the stationary phase is polar and the mobile phase is relatively nonpolar. This means that the stationary phase has a higher affinity for polar compounds, causing them to interact and be retained longer, while nonpolar compounds will move more easily through the column with the mobile phase. This separation technique is commonly used for compounds that are more polar in nature, allowing for effective separation based on their polarities.

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  • 12. 

    ) In ion-pair chromatography 

    Correct Answer(s)
    a large organic counter-ion is added to the mobile phase as an ion-pairing reagent. Separation is achieved either through partitioning of the neutral ion-pair or as a result of electrostatic interactions between the ions in solution and charges on the stationary phase resulting from adsorption of the organic counter-ion.
    Explanation
    In ion-pair chromatography, the addition of a large organic counter-ion to the mobile phase serves as an ion-pairing reagent. This reagent helps in the separation process by either partitioning the neutral ion-pair or by facilitating electrostatic interactions between the ions in solution and the charges on the stationary phase. This interaction occurs due to the adsorption of the organic counter-ion.

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  • 13. 

    In ion chromatography, 

    Correct Answer(s)
    the stationary phase is an ion-exchange resin, and detection is ordinarily accomplished by a conductivity detector.
    Explanation
    Ion chromatography is a technique used to separate and analyze ions in a sample. In this technique, the stationary phase refers to the material that retains the ions and allows for their separation. In ion chromatography, the stationary phase is an ion-exchange resin, which selectively binds and releases ions based on their charge. The detection of ions is typically done using a conductivity detector, which measures the electrical conductivity of the eluent as ions pass through it. This allows for the identification and quantification of different ions present in the sample.

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  • 14. 

    A bulk property detector

    Correct Answer(s)
    responds to some property of the mobile phase (such as thermal or electrical conductivity) that is altered by the presence of analytes.
    Explanation
    A bulk property detector is a type of detector that is able to detect analytes based on changes in a specific property of the mobile phase, such as thermal or electrical conductivity. When analytes are present, they can alter the conductivity or thermal properties of the mobile phase, which can be measured by the detector. This allows the detector to identify the presence of analytes in a sample.

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  • 15. 

     A solute property detector 

    Correct Answer(s)
    responds to some property of analytes, such as absorption or fluorescence.
    Explanation
    The correct answer explains that a solute property detector responds to a property of analytes, such as absorption or fluorescence. This means that the detector is able to detect and measure the presence or concentration of analytes by measuring their absorption or fluorescence properties. This explanation highlights the main function and purpose of a solute property detector in analyzing and identifying analytes in a solution.

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  • 16. 

    List the types of substances to which each of the following chromatographic methods is most applicable:  Gas- Liquid

    Correct Answer(s)
    Species that are somewhat volatile and thermally stable.
    Explanation
    Gas-liquid chromatography is most applicable to species that are somewhat volatile and thermally stable. This is because in gas-liquid chromatography, the sample is vaporized and carried by an inert gas through a liquid stationary phase. The separation of the components in the sample is based on their affinity for the stationary phase and their volatility. Therefore, species that are somewhat volatile and thermally stable are ideal for gas-liquid chromatography as they can be easily vaporized and do not decompose at the temperatures used in the process.

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  • 17. 

    What ways are normal- phase partition chromatography and adsorption chromatography similar?

    Correct Answer(s)
    The stationary phases in both are polar, whereas the mobile phases are relatively nonpolar
    Explanation
    Both normal-phase partition chromatography and adsorption chromatography have polar stationary phases and relatively nonpolar mobile phases. This similarity in the polarity of the stationary and mobile phases allows for the separation of compounds based on their polarity. In both techniques, polar compounds have stronger interactions with the polar stationary phase, causing them to be retained longer and elute later, while nonpolar compounds have weaker interactions and elute earlier. This similarity in the phase polarity is essential for the effective separation of compounds in both normal-phase partition chromatography and adsorption chromatography.

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  • 18. 

    What types of species can be separated by HPLC but not GC? 

    Correct Answer(s)
    Nonvolatile and thermally unstable compounds can be separated by HPLC by not GC
    Explanation
    High Performance Liquid Chromatography (HPLC) is a technique used to separate and analyze nonvolatile compounds that cannot be vaporized without decomposition. It is also effective in separating thermally unstable compounds that may decompose at high temperatures required for Gas Chromatography (GC). In contrast, GC is suitable for separating volatile compounds that can be vaporized without decomposition. Therefore, nonvolatile and thermally unstable compounds can be separated by HPLC but not GC.

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  • Mar 02, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Apr 22, 2012
    Quiz Created by
    Kimloan617
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