Mass spectrometric tracer pulse chromatographic investigations of eluent sorption with bonded RPLC packings.
The experimental technique of mass spectrometric tracer pulse chromatography was used to investigate the uptake of RPLC eluents by a C 18-bonded packing. The experiments were carried out with eluents consisting of binary aqueous mixtures with acetonitrile, methanol, and tetrahydrofuran over the full range of eluent composition at 25 degrees C. The primary experimental data obtained were excess volumes of sorption for the eluent components. The excess volume data were then used to determine the absolute volume of each eluent component in the stationary phase as a function of composition. The absolute volumes were calculated by utilizing a series of strategies specific to limited eluent composition range. The linear inflection region of the excess volume isotherms was used to calculate the volume and composition of the eluent in the stationary phase for organic-rich eluents. Three different assumptions were used and evaluated for the water-rich eluent compositions. The assumptions were (i) constant volume of the sorbed layer, (ii) constant amount of water sorbed, and (iii) no water sorption. The latter assumption was adopted as the most satisfactory. The calculated void volume data were compared with the retention volume of thiourea and uracil, commonly used dead time markers. Neither thiourea nor uracil proved to be an accurate measure of the kinetic void volume.
Wang
Mei
M
Chemistry Department, University of Mississippi, University, Mississippi 38677, USA.
Mallette
Jennifer
J
Parcher
Jon F
JF