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Choosing a liquid chromatography (LC) column for a particular application can be a surprisingly challenging task. On one hand, column manufacturers give us many options to choose from, including particle types, pore sizes, particle sizes, and different lengths and diameters. On the other hand, we usually don't have time to experimentally evaluate many combinations of these parameters, and sometimes we end up picking something similar to the columns that are already in the drawer. The 'kinetic plot' is a powerful graphical tool that can help leverage the best available theory to help us understand how different combinations of parameters (that is, particle size and length) will perform in terms of the time needed to get to a particular column efficiency (and thus resolution), and therefore make well-informed decisions when choosing columns., In the last two instalments of 'LC Troubleshooting', we reviewed the basic idea of a 'kinetic plot' (1) and how to make the plots from experimental data or data from [...]

Choosing a liquid chromatography (LC) column for a particular application can be a surprisingly challenging task. On the one hand, column manufacturers provide us with many options to choose from, including particle types, pore sizes, particle sizes, and different lengths and diameters. On the other hand, we usually do not have time to experimentally evaluate many combinations of these parameters, and sometimes we end up picking something similar to the columns that are already available. The 'kinetic plot' is a powerful graphical tool that can help leverage the best available theory to help us understand how different combinations of parameters (that is, particle size, length, among others) will perform in regard to the time needed to get to a particular column efficiency (and thus resolution), and therefore make well-informed decisions when choosing columns., In last month's instalment of 'LC Troubleshooting', we discussed the basic idea of a 'kinetic plot' and how we can ultimately use this graphical tool to make informed decisions when [...]

Choosing a liquid chromatography (LC) column for a particular application can be a surprisingly challenging task. On the one hand, column manufacturers give us many options to choose from, including particle types, pore sizes, particle sizes, and different lengths and diameters. On the other hand, we usually do not have time to experimentally evaluate many combinations of these parameters, and sometimes we end up picking something similar to the columns that are already in the drawer. The 'kinetic plot' is a powerful graphical tool that can help leverage the best available theory to help us understand how different combinations of parameters (such as particle size and length) will perform in relation to the time needed to get to a particular column efficiency (and thus resolution), and therefore make well-informed decisions when choosing columns., Fifty years into the evolution of modern liquid chromatography (LC) we are still observing remarkable growth in the commercial offerings of LC columns. Each year, we see introductions of columns [...]

Dispersion (broadening, or spreading) of analyte zones (peaks) outside of chromatography columns can seriously erode the resolution provided by good columns. In this final instalment of the series we focus on the impact of elution mode (isocratic or gradient) and postcolumn flow splitting on the total level of extracolumn dispersion (ECD) in a liquid chromatography (LC) system, and demonstrate the use of a free, web-based calculator that can be used to guide decision making aimed at reducing ECD during method development., In the three instalments of 'LC Troubleshooting' published in May, June, and July 2021 we reviewed the basic concepts of extracolumn dispersion (ECD) (1), and discussed the contributions of the [...]

Dispersion (broadening, or spreading) of analyte zones (peaks) outside of chromatography columns can seriously erode the resolution that good columns provide. In this instalment, we focus on the contributions of dispersion in connecting tubing and detectors to the total level of extracolumn dispersion in a liquid chromatography (LC) system., In the instalments of 'LC Troubleshooting' from the last two months, we reviewed the basic concepts of extracolumn dispersion (ECD) (1), mentioned how the level of ECD associated with a [...]

Dispersion (broadening, or spreading) of analyte zones (peaks) outside of chromatography columns can seriously erode the resolution provided by good columns. In this instalment, we focus on the contribution of the sample injection step to the total level of extracolumn dispersion in a liquid chromatography (LC) system. This contribution has both a physical component (that is impacted by injector design and configuration and method variables) and a chemical component (that depends on the difference between the mobile phase and the sample solvent compositions)., In last month's instalment of 'LC Troubleshooting' (1), we reviewed the basic concepts of extracolumn dispersion (ECD), and how the level of ECD associated with a particular instrument can impact [...]

Dispersion (the broadening or spreading) of analyte zones (peaks) outside of chromatography columns can seriously erode the resolution provided by good columns. Understanding the relationship between the level of dispersion associated with a given instrument relative to the intrinsic efficiency of a given column can help avoid disappointing results, especially when switching to new column technologies. In this instalment, we focus on basic concepts in extracolumn dispersion as a prelude to future instalments that will focus on dispersion in specific elements of high performance liquid chromatography (HPLC) systems., Even from the very early days of he development of chromatography 'systems' that provided for mechanized introduction of samples into the mobile phase flow path, it was recognized that dispersion [...]

This instalment is the first of a series of four white papers on high performance liquid chromatography (HPLC) modules (pump, autosampler, UV detector, and chromatography data system) to be published [...]