Patent ID: 7977109

Claim:
A method for enriching at least one nucleic acid with a length of not more than 300 nucleotides relative to at least one least one nucleic acid with a length of more than 300 nucleotides, comprising i) providing a fluid phase P 1 comprising (α1) said at least one nucleic acid with a length of not more than 300 nucleotides, and (α2) said at least one nucleic acid with a length of more than 300 nucleotides, ii) contacting the phase P 1 with an anion exchange matrix to bind the nucleic acid (α1) to the anion exchange matrix, wherein the anion exchange matrix comprises a functional group selected from the group consisting of amino groups, phosphine groups, hydrazine groups and imine groups; iii) optionally washing the anion exchange matrix with a washing buffer, wherein the nucleic acid (α1) remains bound to the anion exchange matrix, and iv) eluting the nucleic acid (α1) bound to the anion exchange matrix from said anion exchange matrix by a method comprising contacting said anion exchange matrix with an aqueous elution buffer comprising a uniform concentration of a salt to obtain a fluid phase P 2 comprising the nucleic acid (α1), wherein the elution buffer comprises a salt selected from the group consisting of: a water-soluble calcium salt, a water-soluble magnesium salt, a water-soluble ammonium salt, and mixtures thereof.