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Numerical and experimental investigation of analyte breakthrough from sampling loops used for multi-dimensional liquid chromatography

Tijdschriftbijdrage - Tijdschriftartikel

Two-dimensional liquid chromatography is increasingly being used to address challenging separations in fields ranging from pharmaceutical analysis to the food industry. A significant impediment to development of more methods is the lack of a complete theoretical foundation upon which sound development decisions can be made. One parameter that is currently not fully understood is the extent of filling of sampling loops in the case where effluent from the first dimension separation is transferred to the second dimension separation through this type of open loop interface. This is a highly important parameter because it is connected to several other variables in a 2D-LC system, including the first dimension flow rate, the sampling (modulation) time, and the loop volume. In this study we have used both numerical simulation methods and experimental measurements to understand the extent to which sampling loops can be filled before a significant fraction of the analyte is lost from the end of the loop. Variables included in the study are the analyte diffusion coefficient (D-mol), loop filling rate (F-fill), loop inner diameter or radius (R-loop) and loop volume (V-loop). For a straight loop capillary we find that analyte breakthrough curves (as measured at the loop outlet) depend only on a single the dimensionless parameter t* = V-loop/F-fill . D-mol/R-loop(2). As a function of this parameter, the fraction of analyte lost from the loop outlet for different extents of loop filling could be calculated, allowing to develop guidelines for the maximum permissible extent of filling before a specified level of analyte loss is reached. Breakthrough measurements using a coiled loop capillary show that less breakthrough is observed compared to the straight capillary at high filling flow rates, presumably due to secondary flows that increase radial dispersion. These measurements enabled the calculation of apparent radial diffusion coefficients for use with coiled capillaries such that the same relation for t* can be used to predict analyte loss due to breakthrough. These results should be very useful to practitioners of 2D-LC, enabling them to make rational decisions about the extent of loop filling on the basis of experimental conditions and analyte type. (c) 2020 Elsevier B.V. All rights reserved.
Tijdschrift: Journal of chromatography
ISSN: 0021-9673
Volume: 1626
Jaar van publicatie:2020
Trefwoorden:Breakthrough, Numerical simulations, Loop coiling, Analyte loss curve, Loop filling, Two-dimensional liquid chromatography
CSS-citation score:1
Toegankelijkheid:Open