Solid phase extraction devices for sample preparation are disclosed, comprising a hollow conical tube having one narrower opening and one broader opening, wherein the narrower opening of the tube contains a solid phase extraction material comprising a functionalized monolithic sorbent, and wherein the solid phase extraction device is prepared by a combination of reduced pressure, positive pressure and mechanical compaction. The solid phase extraction devices are adapted for preparation of small sample volumes, and provide excellent recovery of analytes and good flow characteristics. Methods for preparing and using the solid phase extraction devices are disclosed.