Methods of Nucleic Acid Fractionation and Detection

A method of purifying a nucleic acid from a biological sample, comprising the steps of:

• a) combining the biological sample with a lysis buffer to form a lysis mixture comprising nucleic acid released from cells in said biological sample;
• b) applying a volume of the lysis mixture to size-exclusion chromatography medium in a column comprising a loading end, an eluting end, and a volume of size-exclusion medium, wherein said volume of lysis mixture is 0.35 to 0.8 of the volume of the size-exclusion medium, and allowing lysis mixture to completely enter the size-exclusion chromatography medium;
• and
• c) providing a positive pressure differential to the loading side of the column forcing interstitial fluid containing nucleic acid from to drain from SEC medium, and collecting drained fluid containing nucleic acid for further amplification or analysis.