Page 223 - Vogel's TEXTBOOK OF QUANTITATIVE CHEMICAL ANALYSIS

ION EXCHANCE CHROMATOCRAPHV 7.3

is called the eluate. The liquid entering the ion exchange column may be termed
the influent and the liquid leaving the column is conveniently called the effluent.
If a solution of a suitable eluant is passed through a column charged with an
ion B the course of the reaction may be followed by analysing continuously the
effluent solution. If the concentration of B in successive portions of the eluate
is plotted against the volume of the eluate, an elution curve is obtained such
as is shown in Fig. 7.1. It will be seen that practically al1 the B is contained in
a certain volume of liquid and also that the concentration of B passes through
a maximum.

Volume of eluate, mL
Fig. 7.1

If the ion exchange column is loaded with several ions of similar charge, B,
C, etc., elution curves may be obtained for each ion by the use of appropriate
eluants. If the elution curves are sufficiently far apart, as in Fig. 7.2, a quantitative
separation is possible; only an incomplete separation is obtained if the elution
curves overlap. Ideally the curves should approach a Gaussian (normal)
distribution (Section 4.9) and excessive departure from this distribution may
indicate faulty technique and/or column operating conditions.

Volume of eluate, mL
Fig. 7.2

The rate at which two constituents separate in the column is determined by
the ratio of the two corresponding distribution coefficients, where the distribution
coefficient is given by the equation