Polyethylene membranes sample washing

Five millimeter diameter disks of a porous polyethylene membrane, used as a window material in disposable FT-IR cards manufactured by 3M Corp. (Fisher Cat. 14385-861), were prepared by pre-wetting with 2 pi of methanol. A 1 pi aliquot of the aqueous protein solution was then added, and the membrane allowed to air dry at room temperature, before addition of 2 pi of matrix solution and final air drying. For those samples that were washed, after the protein solution had dried the membrane spot was vortexed in an aqueous 50% methanol solution for 30 seconds and air dried before addition of the matrix solution. 

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