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Consider the following changes that could be applied to the operating parameters for a chromatogram set up to carry out high-performance liquid chromatography (HPLC) with a polar stationary phase and a non-polar mobile phase: I decreasing the viscosity of the mobile phase II using a more tightly packed stationary phase III using a mobile phase that is more polar than the stationary phase Which of the changes would be most likely to reduce the retention time of a sugar in the HPLC? A - VCE - SSCE Chemistry - Question 20 - 2020 - Paper 1

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Consider-the-following-changes-that-could-be-applied-to-the-operating-parameters-for-a-chromatogram-set-up-to-carry-out-high-performance-liquid-chromatography-(HPLC)-with-a-polar-stationary-phase-and-a-non-polar-mobile-phase:--I--decreasing-the-viscosity-of-the-mobile-phase-II--using-a-more-tightly-packed-stationary-phase-III--using-a-mobile-phase-that-is-more-polar-than-the-stationary-phase--Which-of-the-changes-would-be-most-likely-to-reduce-the-retention-time-of-a-sugar-in-the-HPLC?--A-VCE-SSCE Chemistry-Question 20-2020-Paper 1.png

Consider the following changes that could be applied to the operating parameters for a chromatogram set up to carry out high-performance liquid chromatography (HPLC)... show full transcript

Worked Solution & Example Answer:Consider the following changes that could be applied to the operating parameters for a chromatogram set up to carry out high-performance liquid chromatography (HPLC) with a polar stationary phase and a non-polar mobile phase: I decreasing the viscosity of the mobile phase II using a more tightly packed stationary phase III using a mobile phase that is more polar than the stationary phase Which of the changes would be most likely to reduce the retention time of a sugar in the HPLC? A - VCE - SSCE Chemistry - Question 20 - 2020 - Paper 1

Step 1

I decreasing the viscosity of the mobile phase

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Answer

Decreasing the viscosity of the mobile phase generally increases the flow rate, which can lead to a reduction in retention time. This is because less viscous mobile phases can move through the column more easily, thereby reducing the time that analytes spend in the stationary phase.

Step 2

II using a more tightly packed stationary phase

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Answer

Using a more tightly packed stationary phase can actually increase the retention time. While this can improve separation efficiency, it creates more resistance to the flow of the mobile phase, which can lead to longer retention times.

Step 3

III using a mobile phase that is more polar than the stationary phase

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Answer

Using a mobile phase that is more polar than the stationary phase can significantly reduce retention time for polar analytes, such as sugars. In this case, polar analytes would be more likely to remain in the mobile phase rather than interact with the stationary phase, thereby reducing retention time.

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