CHROMA SPIN columns are packed with gel filtration resin and enable rapid purification and size selection of nucleic acid samples. The columns can be used to purify single- or double-stranded DNA or RNA from contaminants such as salts, solvents, enzymes, or proteins. Molecules larger than the particular matrix pore size are eluted out of the column while smaller molecules are retained inside the column matrix. As a result, these columns are ideal for size fractionation of libraries or for removal of primers.