homework solutions13 - Homework Solutions for Chem 422...

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Homework Solutions for Chem 422 Chapter 26 1. a) Elution is the process of washing substances through a chromatographic column with the mobile phase. b) The mobile phase in chromatography is the one that moves over or through an immobilized phase in a column or on the surface of a plate. c) The stationary phase in a chromatographic column is a solid or liquid that is fixed in place. d) The distribution constant (K) in chromatography is the ratio of the concentration of the analyte in the stationary phase to its concentration in the mobile phase when the two phases are in equilibrium. e) The retention time (t R ) for an analyte is the time between its injection onto a column and the appearance of its peak as it elutes from the column. f) The retention factor (k) is the ratio of the amount of analyte in the stationary phase to the amount in the mobile phase. It is generally calculated by k’ = (t R - t M )/t M = t R ’/t M . g) The selectivity factor ( α ) of a column for two analytes (A eluting before B) is given by α = K B /K A = k’(B)/k’(A) = t R ’(B)/t R ’(A). h) The plate height (H) of a chromatographic column is defined by the relationship H = σ 2 /L, where σ is the standard deviation of the concentration distribution for the analyte in its elution band (in units of length) and L is the length of the column packing.
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