Chrom-MS Section 1.4

1.5 Questions

1. List the three basic types of chromatography. What are the subcategories of each type?

2. What does confirmatory analysis mean with respect to chromatography? What two ways can it be accomplished?

3. What are mobile and stationary phases in chromatography?

4. With respect to GC and LC, what types of gradients are used to improve analyte separation?

5. Hand draw a chromatography with a solvent peak and two analytes. Label components of the diagrams with respect to retention time.

6. Explain the old adage “like dissolves like” with respect to chromatography.

7. What possible intermolecular forces can be involved in “like dissolves like?”

8. How are time, gas/liquid volume, and flow rate related in GC and LC?

9. Why is retention time so important in chromatography?

10. Explain the concept of capacity factor, k’. Is k’ a factor for one analyte or many analytes?

11. How is the capacity factor related to retention time of an analyte?

12. What are the acceptable range for k’ for traditional chromatography?

13. How are the capacity factor and the selectivity factor mathematically related?

14. What is the value/purpose of using the selectivity factor?

15. What are acceptable values for selectivity factors?

16. Explain the theoretical plate height, H. What is the origin of H?

17. How is the total number of plates in a column related to the length of the column and H?

18. Why is proper column packing so important in packed-column GC and LC?

19. Explain resolution with respect to chromatography. What is the mathematical relationship between resolution and retention time and peak width?

20. Explain each component in the governing equation for resolution, equation 1.23.

21. How is equation 1.23 used to improve separation of chemically similar analytes in GC and LC?

22. Using the data in Table.1 1 and Example 1.1, calculate k’, α, Rs, H, and N for iso-octane and n-heptane.

23. Why do capillary columns provide higher resolution as compared to packed columns?

24. Draw a van Deemter curve for a GC analysis and explain each factor that contributes to H.

25. Use figures and words to explain the “General Elution Problem.” How is this solved in GC and LC?

26. Why is instrument calibration so important in chromatography?

27. What is the difference in internal and external calibration?