Problem Set #2
Evaluation of column performance in liquid chromatography is a topic of
In two discussions of this topic (see "Testing Procedures for Liquid
Chromatographic Columns", R. E. Pauls and R. W. McCoy, J. CHROMATOGR. SCI.,
, 66-69, and "Evaluation of Column Performance in Liquid Chromatography",
Lane C. Sander, J. CHROMATOGR. SCI.,
, 380-387.), there are two parameters
we did not discuss during the lectures on fluid flow through packed beds.
They are the
column flow resistance,
, and the column impedance, E.
They are expressed by:
For both of these unitless parameters, should the calculated numbers increases or
decrease with increasing column "quality"? Explain.
A Beckman Ultrasphere 5
m particle diameter, 25cm x 4.6 mm i.d. column
operated at 1.55 mL/min with a mobile phase of 80:20 methanol/water showed a
pressure drop of 2250 psi with a total porosity (
) of 0.49.
Assuming the viscosity of the
mobile phase was 1.01 cP, calculate the value of
The typical values of
are in the range of 600-900.
What are the typical values of
As a recently hired analytical chemist in a new methods development group, you
are asked to set up a GC analysis for some newly synthesized compounds.
What factors are important in choosing a GC stationary phase for a given
List as many decision making criteria as possible.
Until about ten years ago there was much interest in
two liquid GC
phases to create a unique GC phase for a particular separation (see, for example, R. L.
Pecsok and J. Apffel, ANAL. CHEM.,