Abstract: A method for assay of an analyte and assay device therefor. The assay device includes an assay component affixed to a permeable membrane. The membrane preferably rests on a permeable membrane support and covers an opening through a receptacle for holding a liquid. The support is adjacent the open upper end of a double ended needle, the lower end of which is adapted to puncture a plug inserted in an open end of a preevacuated container. Puncturing of the plug establishes fluid communication between the prevacuated interior of the container and the opening in the receptacle whereby liquid in the receptacle is passed through the membrane. The membrane has a bubble point sufficient to prevent passage of air through the membrane after all of the liquid has been pulled through as long as the membrane remains wet so that vacuum in the tube is not lost. The device may be part of an assay workstation which comprises a canister and various utensils useful in performing the assay.