In various embodiments a fluid control device suitable for high pressure analytical instruments includes a housing having an interior surface with an end wall. The interior surface defines a chamber. A valve assembly disposed in the chamber controls the flow of fluid through the chamber. An end cap is disposed in the housing opposite the end wall to enclose the chamber. The end wall and end cap each have an opening to pass a fluid to the chamber or to remove a fluid from the chamber. The housing and end cap each has an abutment surface to receive the other abutment surface. At least one of the abutment surfaces has a plastic seal coating. A means of compression, such as a compression housing and compression sleeve, is included to engage the end cap to deform the plastic seal coating between the abutment surfaces and thereby seal the chamber.