21. Sample retention in the column is measured by

A. retention time
B. retention factor
C. retention index
D. all of these

22. Column bleeding occurs when

A. elution of the analyte is extended over time
B. the column is cracked and stationary phase leaks out
C. traces of the stationary phase are eluted
D. the column breaks during installation and causes personal injury

23. Which of the following are not used as stationary phases in a GC column?

A. Polysiloxanes
B. Silica
C. Cyclodextrins
D. None are used as stationary phases

24. Doubling the column’s length increases resolution by a factor of

A. (2)^0.5
B. 2
C. 3
D. 4

25. Sample injection is considered successful if

A. all of the samples in the injector has been added to the column
B. the sample is concentrated at the start of the column
C. the sample is spread evenly along the column
D. the sample is homogenously spread along the column