|Wang, Mei -|
|Avula, Bharathi -|
|Parcher, Jon -|
|Khan, Ikhas -|
Submitted to: Journal of Chromatography A
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 24, 2011
Publication Date: December 2, 2011
Citation: Wang, M., Avula, B., Parcher, J.F., Khan, I.A. 2011. Comparison of concentration pulse and tracer pulse chromatography: experimental determination of eluent uptake by bridged-ethylene hybrid ultra high performance liquid chromatography packings. Journal of Chromatography A. 1220:75-81. Interpretive Summary: Tracer pulse and concentration pulse experiments are used to study the uptake of eluent in the BEH UHPLC packings. Both experimental techniques produce equivalent results, and can be used to measure accurate void volume and excess volume data for systems that are very difficult to investigate by other methods. The experimental results indicate that even the most modern BEH UHPLC packings either adsorb or absorb significant amounts of eluent from aqueous-organic mobile phases commonly used in LC applications. The methods reported herein will extend the ability to better understand the LC retention mechanisms.
Technical Abstract: Excess volume isotherms of acetonitrile and methanol sorbed on a C18 BEH UHPLC packing were determined over a range of pressure, temperature, flow rate and eluent composition. The isotherm measurements were carried out by two independent experimental methods, viz., concentration pulse and tracer pulse chromatographies. Isotherms were measured with both experimental techniques at 30, 45 and 60 degrees celcius. The excess isotherms increased with decreasing temperature although the variations were relatively small. Direct comparison of the two experimental techniques showed that the measured void volumes were identical within experimental error. The measured excess volumes by both techniques were comparable with the concentration pulse experiments producing slightly higher excess volume data with highly aqueous eluents. Both experimental techniques show some variations of the retention volumes with sample volume, sample composition, flow rate and column inlet pressure. The results confirmed the validity of both concentration and tracer pulse chromatographies for the determination of column void volumes and the excess volume of eluent taken up by UHPLC packings.