Referring now to FIG. 3, the preferred embodiment of the invention, collection tube assembly 20 comprises a plastic tube 10a, having a sidewall 11a extending from opened end 16a to a closed 18a. A barrier coating 25 extends over a substantial portion of the outer surface of the tube with the exemption of open end 16a. Barrier coating 25 comprises a first layer 26 of a polymer material, such as an acrylate material and a second layer 27 of a mixture of a Group IVA metal oxide material and silicon oxide based composition and a third layer 28 of an organic overcoating layer such as PVDC.