Introduction to Chromatography Homework Problem Set
This problem set was developed by S.E. Van Bramer for Chemistry 366 at Widener University.
Goal:
To introduce students to chromatographic separations
Objectives:
- Students will be familiar with terms commonly used for chromatographic separations
- Students will understand the variables used to describe chromatographic performance
- Students will understand the effect of changing instrument parameters on chromatographic performance
- Students will be able to describe how separation occurs in gas and liquid chromatography
Introduction:
Retention
- Describe the function of the stationary phase and the mobile phase.
- Describe the relationship between the mobile phase flow rate and the linear velocity for both open tubular and packed columns.
- For a chromatographic separation with the following retention times: Mobile phase 30.0 s, Compound A 60.0 s; Compound B 75 s. Determine the adjusted retention time for each compound, the retention factor for each compound, and the selectivity factor for the column.
- For this chromatographic system, predict the retention time for a compound with a retention factor of 1, 5, and 10.
- What happens to the retention time for a compound if the equilibrium between the stationary and mobile phases, Kc, increases?
- What happens to the retention time for a compound if the volume of the stationary phase increases?
- What happens to the retention time for a compound if the volumetric flow rate increases?
Band Broadening
- The peak width at half height in the above analysis for; A = 0.50 s and B = 0.54 s. If the separation is with a 15 cm column, determine the number of theoretical plates and the theoretical plate height.
- Calculate the resolution for this separation.
- If the number of theoretical plates is doubled, what happens to the resolution for this separation.
Band Theory
Given the equation:
H = A + B/u + Csu+ CM u
- Explain the effect of increasing the mobile phase flow rate. What are the tradeoffs and how is this parameter optimized?
- Explain the effect of reducing the stationary phase thickness. What are the tradeoffs and how is this parameter optimized?
- Explain the effect of reducing the column diameter. What are the tradeoffs and how is this parameter optimized?
- For a packed column, explain the effect of reducing the size of the packing material. What are the tradeoffs and how is this parameter optimized?
- Explain the effect of increasing the column length. What are the tradeoffs and how is this parameter optimized?
- Explain the effect of changing the temperature. What are the tradeoffs and how is this parameter optimized?
- Explain the effect of changing the solvent. What are the tradeoffs and how is this parameter optimized?
Please send comments or suggestions to svanbram@science.widener.edu
Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013
© copyright 1996, S.E. Van Bramer
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Last Updated: February 12, 2007