Funnel-shaped sample-vial septum with membrane covered diffusion-barrier section

Abstract

A funnel-shaped monolithic low-density polyethylene sample-vial septum comprises a flange, a capture wall, a diffusion-barrier wall, and a membrane. The capture wall is conical, extending from its truncated apex at the diffusion barrier wall to its mouth about which the flange is disposed. The membrane is disposed at the end of the diffusion-barrier wall away from the capture wall. This structure defines a septum aperture, including a conical capture section, defined by the capture wall, and a cylindrical diffusion-barrier section, defined by the diffusion-barrier wall. The 7.0 mm length of the diffusion-barrier section is 12/mm times the square of its diameter 0.76 mm. The diameter of the diffusion-barrier section which is selected to be 0.05 mm greater than the diameter of the largest needle to be used with the septum, i.e., a 22 gauge needle typically used for liquid chromatography. The minimum thickness of the membrane is 0.05 mm so that a blunt 26 gauge needle will not be damaged while piercing the membrane. The membrane has a curved surface facing the capture section. The radius of curvature of this surface is 7.0 mm, set equal to the barrier section length. This is a result of a molding tool tip that is curved so that if misaligned, the desired minimum membrane thickness is still achieved. Prior to piercing, the membrane serves as a solid barrier to evaporative sample loss. After piercing, the long diffusion-barrier section serves as an effective barrier to evaporative sample loss.

Dependencies are inferred from the claim text.