An apparatus comprising a fluid communication device configured to extend from a drill string and establish fluid communication with a subterranean formation penetrated by a wellbore in which the drill string is positioned, wherein the drill string comprises a passage configured to conduct drilling mud and an opening extending through an outer surface thereof and into a cavity. A sample chamber is coupled within the cavity and is in selectable fluid communication with the formation via the fluid communication device. A retainer is configured to absorb axial loading of the sample chamber within the cavity.