Effects of the gradient profile, sample volume and solvent on the separation in very fast gradients, with special attention to the second-dimension gradient in comprehensive two-dimensional liquid chromatography

Possibilities of retention prediction in fast gradient liquid chromatography. Part 3: Short silica monolithic columns

“…(12) (15), which predict decreasing k e at increasing starting concentrations of ACN, A. At a constant gradient time, t G = t, however, increasing A is automatically connected with decreasing gradient slopes, B:…”

“…Hence, columns with high permeability and low flow resistance should be used, whenever possible, such as core−shell or monolithic columns [14]. At the optimum flow rate, appropriate adjustment of the gradient mobile phase composition range provides the most efficient optimization tool for gradient separations [8,[11][12][13]. The gradient range may affect sample peak capacity equally or even more significantly than the length of monolithic columns or of columns packed with core−shell particles [28].…”

“…Recently, we have applied the theory of gradient elution for prediction of retention data and optimization of fast second-dimension gradients in two-dimensional LC × LC [2,[10][11][12]. Because of rapid changes in mobile phase composition during the fast gradients, short gradient times used in the repeated fraction transfer cycles impose that the column must be rapidly re-equilibrated to the initial conditions between the repetitive gradient analyses [13].…”

Repetitive injection method: A tool for investigation of injection zone formation and its compression in microfluidic liquid chromatography

“…Injection-related band broadening is observed in many LC scenarios [8], such as in 2D LC [9], where relatively large volume fractions from the first dimension (often dissolved in strong solvents), are directly injected to the second dimension column. While we limit our attention to LC experiments in this work, the same concepts apply to two dimensional experiments or in general, whenever large sample volumes are injected on LC columns.…”

Theory and Practice of UHPLC and UHPLC–MS

“…Hence, the number of resolved peaks increases when simultaneous gradients are used in the first dimension and in the second dimension of a comprehensive online 2D setup (Jandera, 2012a). Optimization of the gradient range and gradient profile, especially in the second dimension, can significantly increase the practical 2D peak capacity Jandera et al, 2011).…”