Invisible analyte peak deformations in single-component liquid chromatography.
It is well known that if a small excess of solute is injected into a chromatographic system equilibrated with an eluent containing the same solute, a single so-called perturbation peak will appear in the chromatogram. It was recently shown (Samuelsson, J.; Forssén, P.; Stefansson, M.; Fornstedt, T. Anal. Chem. 2004, 76, 953-958) that this peak consists of displaced plateau molecules; the injected molecules (mass peak) elute later, together with a deficiency of plateau molecules and are therefore not detected. In this article, we investigated what happens if a large rather than a small excess of solute molecules is injected. To study this systematically, the experimental method involved an enantiomer pair in an achiral separation system. It was found that the invisible mass peak was extremely deformed and that its shape depended on the amount of excess injected, the eluent concentration, and the column length. Depending on these operational conditions, the mass peak changed from a classical Langmuirian (tailing) to an anti-Langmuirian (leading) shape, with deformed shapes observable in the transition. The visible, overloaded perturbation peak was always Langmuirian, regardless of the mass peak shape.
Samuelsson
Jörgen
J
Department of Physical and Analytical Chemistry, Uppsala University, BMC Box 577, SE-751 23, Uppsala, Sweden.
Arnell
Robert
R
Fornstedt
Torgny
T