In order to successfully tackle the truly complex separation problems arising from areas such as proteomics research, the development of multi-dimensional separation technology is required. On-line and off-line two-dimensional LC systems are designed such to achieve the highest peak-production rate (peak-capacity-per-unit-time) by optimizing column dimensions and LC conditions (flow rate, gradient time, and sampling volume).
Spatial two-dimensional separations differ from separations in the time domain in that component peaks are characterized by their x and y coordinate in the separation space. Since all second-dimension separations are developed in parallel, the analysis time can be greatly reduced compared to coupled-column 2D-LC (sequential analysis). The spatial 2D-LC micro-fluidic device features a single channel for the first-dimension separation, and an array of parallel channels for the second-dimension separations. To distribute the second-dimension mobile phase homogeneously across the entire cross-section, a flow distributor consisting of an ordered bed of diamond-shaped pillars has been incorporated on-chip.
Extending spatial 2D to 3D-LC, a 3D device targeting the analysis of highly complex proteomics samples will be created. This spatial 3D-LC chip has the potential to yield unrivaled chromatographic resolution for biomarker discovery, providing unique profiling possibilities for complex proteomics mixtures encountered in biomarker discovery studies.
Selected reading
S. Eeltink, S. Dolman, G. Vivo-Truyols, P. Schoenmakers, R. Swart, M. Ursem, G. Desmet; Selection of column dimensions and gradient conditions to maximize the peak production rate in comprehensive off-line two-dimensional liquid chromatography using monolithic columns. (Anal. Chem. 2010, 82, 7015-7020).
D.J.D. Vanhoutte, S. Eeltink, W.Th. Kok, P.J. Schoenmakers; Construction and application of an apparatus for spatial comprehensive two-dimensional liquid chromatography (Anal. Chim. Acta, 2011, 701, 92-97).