A method for separating and collecting cell-free plasma by finger stick that minimizes contamination with genomic DNA from a donor. The method comprising placing a tourniquet on one of the digits of the donor's finger to apply pressure, lancing the digit to create an incision in the digit, and collecting blood from the incision from the incision site. The collected blood is placed on a separation membrane wherein the separation membrane is in contact with a collection membrane and both the separation and collection membrane are inserted into a substrate configured to provide overlap between the membranes. A kit and instructions for carrying out the method is also provided.