Temperature-Assisted On-Column Focusing in Liquid Chromatography
Liquid chromatography (LC) is a versatile and nearly universally-applicable analytical technique used in a variety of industrial, environmental, biomedical, quality control, and academic research applications in which samples are separated into their constituent components in order to determine the concentration and identity of individual components. Column LC, in which components of a mixture pass through a packed bed in a column at different rates based on their unique velocity, is the most commonly used form, but it comes with several limitations. Although a downsized system could lower costs and create less hazardous waste, a smaller LC system is constrained by a low injected volume to column volume ratio and therefore cannot accommodate typical sample sizes. For example, a capillary column with a diameter of 100 μm would only be able to accommodate a maximum sample volume of 2.5 nL, an impractically small quantity.
Description
Temperature-Assisted Solute Focusing (TASF) poses a ready solution to small-column liquid chromatography’s current limitations. Cooling a short portion of the capillary column effectively slows the velocities of the constituents and cause components that would ordinarily be too big to stick to the column during the injection process, concentrating them into a smaller, more acceptable volume. Cooling and heating can be used on the entirety of the column to alter constituent velocities rapidly, permitting efficiency and flexibility in separations using small column sizes. TASF effectively allows smaller column sizes to be used, lowering costs of obtaining high-purity samples and the cost of discarding hazardous waste products.Applications
• Continuous, online microdicodialysis sampling of neurotransmitters• Re-focusing fractions of first-dimension effluent sampled and injected into the second dimension column
Advantages
• Effectively mitigates increases in peak width introduced by injecting large volumes of samples dissolved in solvents that match the mobile phase• Orthogonal to solvent-based focusing methods, allowing its use to
replace or augment solvent-based methods
• Variance-based model facilitates accurate in silico simulation of TASF separations in order to focus temperature, time, and column parameters
• Optimized TASF analyses decrease the concentration detection limit