The invention provides methods of detecting a nucleic acid present in a biological sample, comprising combining the biological sample with a lysis buffer to form a lysis mixture comprising nucleic acid released from cells in said biological sample; and subjecting a volume of the lysis mixture to size-exclusion chromatography in a column comprising a volume of size-exclusion medium. In certain embodiments, the lysis buffer separates double-stranded nucleic acid into single-stranded nucleic acid. In certain embodiments, the elution can have a flow rate of separation of less than 10 minutes to produce an eluted solution comprising isolated nucleic acid. The invention provides for a method of accurately and rapidly detecting products of nucleic acid amplification.