Chromatographic techniques that employ a liquid mobile phase loosely fall into a category referred to as Liquid Chromatography (LC). In LC, the stationary phase is either a solid surface or a surface that has been modified, or coated, to allow for partitioning of solutes into this thin layer of coating. As in GC, separation is achieved due to the differential distribution of solutes between mobile and stationary phases. In LC, the stationary phase is typically in the form of porous or non-porous particles that are “packed” into a metal or glass tube, referred to as the chromatographic column. New developments in this field have introduced the use of monolithic columns, a construct wherein a porous bed is formed in situ, as opposed to the packing of particles into the tubing.

Capillary fills two fundamental roles in LC applications, as connection lines and as columns.  First, it is often used for making fluidic connections between the chromatography columns and the other components of the system, i.e. flow cells, injectors, detectors, etc. Capillary is durable, yet easily cut to the exact length needed for such interfacing. The wide range of available ID’s allows chromatographers great latitude in selecting tubing that offers the optimum performance under their experimental and instrumental design.

Second, trends toward miniaturization of systems has lead to the introduction of capillary-based columns, and thus the advent of Capillary Liquid Chromatography (CapLC). In this technique, a capillary is either packed with particles or used as the substrate for construction of a monolithic bed. The particles, or monolithic bed, contain the stationary phase and the capillary has become the chromatographic column. Capillary diameters most commonly range from 50mm up to 500mm, with a variety of different designs available. Standard TSP products are commonly used with TSU products gaining interest for some monolithic columns.

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