Problem Set 2 - CHM614/714 Problem Set#2 1 Evaluation of...

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1 CHM614/714 Problem Set #2 1. Evaluation of column performance in liquid chromatography is a topic of continuing interest. In two discussions of this topic (see "Testing Procedures for Liquid Chromatographic Columns", R. E. Pauls and R. W. McCoy, J. CHROMATOGR. SCI., 1986 , 24 , 66-69, and "Evaluation of Column Performance in Liquid Chromatography", Lane C. Sander, J. CHROMATOGR. SCI., 1988 , 26 , 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: d p 2 P L  and E h 2 (a) For both of these unitless parameters, should the calculated numbers increases or decrease with increasing column "quality"? Explain. (b) 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 ( T ) of 0.49. Assuming the viscosity of the mobile phase was 1.01 cP, calculate the value of . (c) The typical values of are in the range of 600-900. What are the typical values of E? 2. 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. (a) What factors are important in choosing a GC stationary phase for a given separation? List as many decision making criteria as possible.
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