HPLC column design and method of making same
The disclosed HPLC column is formed with overlying concentric inner and outer tubes. The flow path is established via the inner tube bore that holds packed absorbent, end filters and capping sealing members, and end coupling members cooperate with the inner tube at its ends. The sealing and end coupling members have conventional configurations for establishing a sealed connection with capillary lines and their fittings, for the series flow testing use through the column. The inventive method and manner of assembly provides that the outer tube overlies all of the inner tube and both sealing members, but only part of each end coupling member. The ends of the outer tube are then deformed radially inward to become mechanically interlocked with the end coupling members, as the column, holding also the filters and sealing members within the inner tube.
1. A HPLC column ready to be connected and used in a liquid-tight serial flow circuit between capillary lines having externally threaded end fittings associated therewith, said column comprising
an inner tube; absorbent filling the inner tube; a filter assembly across each inner tube end containing the absorbent; and end coupling members outwardly adjacent the filter assemblies;
a cylindrical outer tube overlying all of the inner tube and each filter assembly, and an inward portion of each coupling member, all arranged in an axially aligned association;
means cooperating between the outer tube and the underlying inward portion of each end coupling member for mechanically holding the outer tube and end coupling members together;
each end coupling having an internally threaded opening suited to cooperate with a respective threaded end fitting, each filter assembly having a sealing bore sized to cooperate in liquid-tight association with a respective capillary line, and the opening and bore being concentrically arranged suited for mechanically connecting the end fittings and capillary lines in said liquid-tight flow connection through the column via the inner tube, absorbent and filter assemblies; and
the outer tube cylindrical outer surface defining the maximum outer radial dimension of the column.
2. A HPLC column according to claim 1 , further wherein the inward portion of each end coupling member underlying the outer tube having an annular groove defined by axially separated generally radial surfaces and a generally axial bottom surface, the bottom groove surface being smaller in diameter than the inner face of the outer tube, and the outer tube proximate each end being configured conically to tightly fit in and terminate within the annular groove and providing the cooperating holding means between the outer tube and the each end coupling member for holding them together.
3. A HPLC column according to claim 2 , further wherein said groove having a depth about equal to the wall thickness of the outer tube and having an axial width in excess of the wall thickness of the outer tube, whereby the outer tube end being at least partly hidden within the groove.
4. A HPLC column according to claim 3 , further wherein the inward radial groove surface having an outer diameter less than the outer diameter of the outward radial groove surface and the outward radial groove surface having an outer diameter more than the inner diameter of the outer tube but less than the outer diameter of the outer tube.