|Enhancing detection limits in chromatography using solvent-assisted post-column refocusing
|Comprehensive Chromatography - The State of the Art
|Mr Vincent Pepermans
|Dr Jelle De Vos
Prof Sebastiaan Eeltink
Prof Gert Desmet
|Vrije Universiteit Brussel (VUB)
Abstract Information :
The detection of trace levels of analytes in liquid-chromatographic analysis constitutes one of the major analytical challenges. The fundamental nature of LC is such that the constituents in a sample mixture are diluted when they are distributed between the mobile and stationary phase, which negatively influences the limit of detection. This is even more detrimental in two-dimensional liquid chromatography (LC x LC), where dilution is even a larger bottleneck since the dilution factors in the two consecutive chromatographic processes are multiplicative.
We report on a generic method for the enrichment of analytes after their separation on an analytical column, prior to detection. In this strategy, the analytes are lead to a trap column packed with particles containing a strongly retaining stationary phase after which they are re-eluted using a strong solvent in a backward elution mode. During this re-elution, the trapped bands are refocused as the strong solvent chases the analytes out of the pores of the particles. It will be demonstrated how, using an optimized trap configuration and elution/remobilization conditions, signal enhancement factors in the order of 10 to 20 can be achieved. Emphasis will also be put on the requirements in viscosity matching between the trapping solvent and the elution solvent. In addition, some general rules for the optimal conditions (trapping time, elution solvent composition, direction of elution) and trap design (particle type, length and cross-section) will be given, in combination with estimates of the maximal degree of refocusing that can be expected. Emphasis will also be put on the possibility to miniaturize the trap columns, and the entailing problems and limitations.