Out-of-class Problems
- Page ID
- 73017
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- What would be the effect on a gas chromatographic peak of introducing the sample at too slow a rate (i.e., making a very slow injection into a gas chromatograph from a syringe)?
- Describe the different contributions to peak broadening in a gas or liquid chromatographic system.
- Consider the gas chromatographic separation of the esters methyl acetate, methyl propionate, and methyl n-butyrate on a column containing a stationary phase of intermediate polarity. What would be the retention order on this column? Would this retention order change if a non-polar stationary phase had been used instead? Explain. Would the retention times change on the non-polar column? Explain.
- What would be the effect of each of the following on the plate height of a gas chromatographic column? Explain each answer by referring specifically to terms in the equation that describes chromatographic peak broadening.
- Increasing the weight of stationary phase relative to the support particles.
- Increasing the flow rate.
- Reducing the particle size of the packing.
- Decreasing the column temperature.
- Describe three general terms that can be adjusted to improve resolution in chromatographic separations and explain specific experimental changes that can be made to adjust these parameters.
- In preparing a benzene/acetone gradient for a silica gel liquid chromatographic column (note, this is silica gel and not a bonded-phase material), is it desirable to increase or decrease the proportion of benzene as the column is eluted? Explain your answer.
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- For a reversed-phase liquid chromatographic separation on a C-18 column, predict the elution order of 4-phenylbutane, 4-phenyl-1-butanol, and 4-phenyl-2-butanone. Explain your answer.
- Suppose the liquid chromatogram of these three compounds came out as shown below. What is the problem with this chromatogram (there is a specific chromatographic term to describe it) and explain specifically what you would do experimentally to improve the chromatography?
