Spectrum's line of adjustable plungers are adjustable length bed supports used to reduce the bed height of a column. They will go into either or both ends of a column to allow for a wide adjustment of the bed height. They are of particular use where gel packings are in short supply, where reverse (ascending) flow is used, when in-stream injection is used, and in any case where the exact bed length is of significance.
Adjustable plungers are available for all of the columns in both aqueous and organic styles. Due to mechanical constraints, there are some differences in the construction of the plungers of different sizes. The plungers for the 0.6, 0.9, 1.5, and 2.5cm I.D. columns have a capillary passage which runs from the plunger face to a fitting outside the column. The larger plungers have a fitting located on the back of the plunger face. The tubing runs down the center of the plunger shaft to this fitting. Both designs are free of mixing cavities and dead volume.
The aqueous plungers make a seal to the glass column using an expanding Viton® O-ring (non-expanding on the 0.6cm column size). The 0.9 and 0.6cm organic plungers use a non-expanding Viton O-ring to make a seal with the glass. The larger organic plungers use an expanding Viton O-ring with a PTFE® shield to provide the ultimate in solvent resistance.
The mesh support used in the plungers is the same 2-layer support used in the column endplates. A 10 micron mesh is in contact with the bed and a 50 micron grid is used to support the mesh. This provides a non-clogging support that minimizes any band spreading as the eluant flows from the packing into the outlet tubing.