Published:Journal of Chromatographic Science,
ISSN 0021-9665 Volume 45,
Number 1, January 2007, pp.6-15
Modeling of Ion-Exclusion and Vacancy Ion-Exclusion
Chromatography in Analytical and Concentration Overload Conditions
Krzysztof Kaczmarski[1], Wojciech Zapala[1], Wojciech
Wanat[1], Masanobu Mori[2], Bronislaw K. Glód[3], and Teresa
Kowalska[4]
[1]Faculty of Chemistry, Technical University of Rzeszów,
Al Powstanców Warszawy 6, 35-959 Rzeszów, Poland;
[2]National Institute of Advanced Industrial Science and Technology
at Seto, 110, Nishiibara-cho, Seto, 489-0884, Japan;
[3]Meat and Fat Research Institute, Jubilerska 4, 04-190 Warsaw,
Poland; and
[4]Institute of Chemistry, Silesian University, 9 Szkolna Street,
40-006 Katowice, Poland
Ion-exclusion chromatography (IEC) finds applications
in various different analytical separations of weak acids. Pure,
deionized water or a diluted, aqueous solution of a strong mineral
acid (such as, e.g., sulphuric acid) is used as the mobile phase,
whereas a typical stationary phase is a strongly acidic resin
in the H+ form (e.g., the sulfonated polystyrene–divinylbenzene
resin with a high ion-exchange capacity, provided by the sulfonic
acid groups). When pure water is used as the mobile phase, then
the characteristic leading (i.e., frontally tailing) peaks are
obtained, and the retention depends mainly on the concentration
of the analyte. An alternative technique is vacancy ion-exclusion
chromatography (v-IEC), in which the column is equilibrated with
the sample solution, flowing as the mobile phase through the system,
and pure water is injected as the sample. In this case, the symmetrical
vacant peaks are obtained. The aim of this paper is to describe
the retention mechanism in IEC and v-IEC for the adsorptive and
nonadsorptive acids in analytical and concentration overload conditions,
with pure water and the diluted sulphuric acid solution as the
two different mobile phases. The retention times and the peak
shapes predicted by the derived equations remain in a good qualitative
and quantitative agreement with the experimental data. The model
proposed in this paper predicts the new features characteristic
of IEC for the adsorptive acids. These are, namely, an increase
in the retention time of the peak apexes (up to a certain level
and concurring with an increase in the acid concentration), followed
by a subsequent decrease of the retention time (with the further
growth of the acid concentration in the eluent). Similar changes
in the retention time observed for v-IEC in the specific adsorption
conditions were also correctly predicted by the model.
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