A base assembly for an adsorptive gas separation system, preferably of a portable medical oxygen concentrator, the base assembly comprising (a) a molded platform comprising a bottom member (52, 137) having a first surface and a second surface generally parallel to the first surface; (b) two or more cylindrical collars (29, 31, 55, 109, 107) attached to the first surface of the bottom member (52, 137) and adapted to detachably receive and support respective ends of two or more cylindrical columns (25, 27, 53, 61, 63); and (c) a ported stator plate (87, 161) attached to the first surface of the bottom member (52, 137), wherein the ported stator plate (87, 161) is part of a rotary valve (65, 171), adapted to direct gas flow in the operation of the adsorptive gas separation system, and wherein the ported stator plate (87, 161) has a central stator port and two or more peripheral stator ports (125, 123, 127, 129), adjacent the first surface of the bottom member (52, 137); wherein (d) a column product port (133, 117, 115, 139, 119) is disposed in the bottom member (52, 137) of the molded platform within each of the two or more cylindrical collars (29, 31, 55, 109, 107); (e) each column product port extends from the first surface of the bottom member (52, 137) to a point intermediate the first surface and the second surface of the bottom member (52, 137); (f) each column product port (133, 117, 115, 139, 119) is adapted to be sealably and removably connected to a cylindrical column (25, 27, 53, 61, 63); (g) and wherein each peripheral stator port (125, 123, 127, 129) is connected to a respective column product port (133, 117, 115, 139) by a passage (145, 143, 135, 141) disposed in the bottom member (52, 137) of the base assembly. (a) a molded platform comprising a bottom member (52, 137) having a first surface and a second surface generally parallel to the first surface; (b) two or more cylindrical collars (29, 31, 55, 109, 107) attached to the first surface of the bottom member (52, 137) and adapted to detachably receive and support respective ends of two or more cylindrical columns (25, 27, 53, 61, 63); and (c) a ported stator plate (87, 161) attached to the first surface of the bottom member (52, 137), wherein the ported stator plate (87, 161) is part of a rotary valve (65, 171), adapted to direct gas flow in the operation of the adsorptive gas separation system, and wherein the ported stator plate (87, 161) has a central stator port and two or more peripheral stator ports (125, 123, 127, 129), adjacent the first surface of the bottom member (52, 137); wherein (d) a column product port (133, 117, 115, 139, 119) is disposed in the bottom member (52, 137) of the molded platform within each of the two or more cylindrical collars (29, 31, 55, 109, 107); (e) each column product port extends from the first surface of the bottom member (52, 137) to a point intermediate the first surface and the second surface of the bottom member (52, 137); (f) each column product port (133, 117, 115, 139, 119) is adapted to be sealably and removably connected to a cylindrical column (25, 27, 53, 61, 63); (g) and wherein each peripheral stator port (125, 123, 127, 129) is connected to a respective column product port (133, 117, 115, 139) by a passage (145, 143, 135, 141) disposed in the bottom member (52, 137) of the base assembly.