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RADIOCHEMISTRY, STABLE ISOTOPES,
NUCLEAR ANALYTICAL METHODS, GENERAL CHEMISTRY
81
Fig.4. Plate heights calculated from elution curves of REE cations obtained on Ion Pac CS3+CG3 column at 35 o C; a)
Sc 3+ , Lu 3+ , Yb 3+ , Tm 3+ , Er 3+ , Ho 3+ , Y 3+ , Dy 3+ and Tb 3+ (Eluent – 80 mmol·L –1 α-HIBA, flow rate – 1 mL·min –1 .
Sample: Sc 3+ – 5 mg·L –1 ; Lu 3+ , Yb 3+ , Tm 3+ and Y 3+ – 10 mg·L –1 ; Er 3+ and Ho 3+ – 20 mg·L –1 ; Dy 3+ – 30 mg·L –1 ; Tb 3+
– 40 mg·L –1 .). b) Eu 3+ , Sm 3+ , Nd 3+ , Pr 3+ , Ce 3+ and La 3+ (Eluent – 220 mmol·L –1 α-HIBA, flow rate – 1 mL·min –1 .
Sample: Eu 3+ – 10 mg·L –1 ; Sm 3+ , Nd 3+ and Pr 3+ – 20 mg·L –1 ; Ce 3+ – 40 mg·L –1 ; La 3+ – 50 mg·L –1 as a function of
reciprocal of the distribution coefficient.).
It is apparent that for elements with relatively low
values of distribution coefficients plate height increases
with 1/λ. For elements more strongly retained
by the resin, however, the opposite trend was
observed, i.e. plate height increased with increasing
λ. In addition, for the elements most strongly
retained by the resin (cerium, lanthanum) the plate
height increased with increasing temperature. Such
behaviour is inconsistent with the Van Deemter
and Glueckauf-Hamilton equations, because these
equations contain no terms in which the distribution
coefficient is in the numerator. Similar phenomenon
was observed earlier when separating
several anions [3] as well as alkali and alkaline earth
cations [4] by ion chromatography. The behaviour
seems to be quite general. Increasing plate height
with increasing distribution coefficient has also been
observed in classical ion exchange chromatography
of REE ethylenediaminetetraacetates on anion-exchange
resins with different cross-linking [5]
and in analogous experiments with alkali and alkaline
earth metals on sulfonic cation exchangers with
different cross-linking [6]. Dybczyński [5] proposed
modifying the Glueckauf-Hamilton equation by
incorporating a fifth term taking into account the
contribution of longitudinal diffusion in the stationary
phase to the total plate height. The possibility
that longitudinal diffusion in the stationary phase
may contribute substantially to the total plate
height was originally foreseen by Giddings [7].
So, in its final form the equation for plate height
is:
Fig.5. Temperature dependence of the plate height (normalized with respect to individual values of the weight distribution
coefficient values) as a function of temperature: a) Lu 3+ , Yb 3+ , Tm 3+ , Er 3+ , Ho 3+ , Dy 3+ and Tb 3+ . Column –
Ion Pac CS3+CG3, flow rate – 1 mL·min –1 , eluent – 80 mmol·L –1 α-HIBA; open circles – λ=2, full circles – λ=20).
b) Eu 3+ , Sm 3+ , Nd 3+ , Pr 3+ , Ce 3+ and La 3+ . Column – Ion Pac CS3+CG3, flow rate – 1 mL·min –1 , eluent – 220
mmol·L –1 α-HIBA; open circles – λ=2, full circles – λ=20.