The document presents results from tests detecting metal ions like Cu2+ and Fe2+ using ion exchange chromatography. Table 5 shows retention times, velocities, and other parameters for Cu2+ and Fe2+. Tests did not detect Ni2+ due to possible errors or experimental conditions. The separation of Cu2+ and Fe2+ was ineffective as peaks overlapped significantly based on similar retention times and factors. A longer column with more theoretical plates is needed to achieve the desired resolution of 1.5 for separating Cu2+ and Fe2+.

1. Discussion
Table 5: Summary table of calculated values
Parameters Cu2+ Fe2+
Retention times 2172s 2351s
Linear velocity of mobile 8.504 x 10-3cms-1 8.504 x 10-3cms-1
phase
Average linear rate of 6.12 x 10-3cms-1 5.66 x 10-3cms-1
retained species
Partition ratios 1 : 1.4 1 : 1.5
Capacity (retention) factor 0.389 0.503
Distribution constant 0.329 0.426
Selectivity factor 0.77 0.77
Number of plates in column 224 294
Height of each plate 0.059cm 0.045cm
Column resolution 0.317 0.317
The experimental procedures show that tests were done to detect the presence of Ni2+ in
the metal ion solution; however, all tests produced negative results. The non-detection of
Ni2+ in the spot tests and separation may be due to random errors of the analysts. It is
possible that the initial flow rate was not adequate for the Ni2+ to elute effectively and the
very small concentrations present may not be observable when doing the spot tests. It
may also have been necessary to lower the pH causing the Ni2+ to be less capable to form
a strong ionic interaction with the stationary phase thus allowing it to elute through the
column.
The effectiveness of the separation was not very good as the Fe2+ and the Cu2+ ions were
eluted at very close times resulting in a significant overlap of the peaks. This can be seen
in the values of the retention times, average linear rates, retention factors, distribution
factor and the selectivity factor being very close or the same. The resolution was found to
be 0.317, a far way from the ideal value of 1.5 which suggests that the separation was
poor due to the column efficiency. Having more theoretical plates with smaller heights
would increase the likelihood of the ions separating. The results suggest that both ions
have very close affinities for the anion exchange resin. In order for separation to be
effected, an anion exchanger that has significantly different affinities for the iron and the
copper species should be used. Changes in the mobile phase composition should affect
the partition, capacity factor, selectivity and thus increase the resolution and the
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2. effectiveness of the separation. Additional calculations were done to find the length of
column required to achieve a resolution of 1.5 in this separation:
N1/N2 = (Rs)12/(Rs)22
N1 = (NCu2+ + NFe2+)/2 = (224 + 294)/2 = 259
Rs1 = 0.317
N2 = [(Rs)2/(Rs)1]2 * N1
= (1.5/0.317)2 * 259
= 5799 plates
Hav = (HCu2+ + HFe2+)/2
= (0.059cm + 0.045cm)/2
= 0.052cm
L = Hav * N2
= 0.052cm * 5799
= 301.548cm
A much longer column (301.548cm) is required length to achieve a resolution of 1.5.
The additional information needed for the complete quantification of the concentrations
of Fe and Cu in the supplied sample is by preparing standard solutions of Fe and Cu and
measure their absorbance in a spectrophotometer at the relevant wavelengths and plot the
results then extrapolate the readings from the standard graph.
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