A method for enriching relatively short nucleic acid from a nucleic acid composition, which comprises: (a) contacting nucleic acid of a nucleic acid composition with a solid phase under association conditions, wherein: (i) the nucleic acid of the nucleic acid composition comprises relatively short nucleic acid and relatively long nucleic acid, (ii) the relatively short nucleic acid is about 300 base pairs or less, (iii) the relatively long nucleic acid is larger than about 300 base pairs, (iv) the solid phase is a collection of particles, the particles comprise silica, and the solid phase does not comprise a functional group that interacts with the nucleic acid, and (v) the association conditions comprise a chaotropic salt and do not comprise a volume exclusion agent; whereby the relatively short nucleic acid and the relatively long nucleic acid are associated with the solid phase; (b) introducing the solid phase after (a) to dissociation conditions that comprise up to 30% volume exclusion agent and a salt, wherein: (i) the salt comprises an ionic salt and is not a chaotropic salt and wherein the ionic salt is at a concentration of 0.25M to 0.5M, and (ii) the relatively short nucleic acid preferentially dissociates from the solid phase under the dissociation conditions as compared to the relatively long nucleic, thereby yielding dissociated nucleic acid; and (c) separating the dissociated nucleic acid from the solid phase, whereby the relatively short nucleic acid is enriched in the dissociated nucleic acid relative to in the nucleic acid composition. (a) contacting nucleic acid of a nucleic acid composition with a solid phase under association conditions, wherein: (i) the nucleic acid of the nucleic acid composition comprises relatively short nucleic acid and relatively long nucleic acid, (ii) the relatively short nucleic acid is about 300 base pairs or less, (iii) the relatively long nucleic acid is larger than about 300 base pairs, (iv) the solid phase is a collection of particles, the particles comprise silica, and the solid phase does not comprise a functional group that interacts with the nucleic acid, and (v) the association conditions comprise a chaotropic salt and do not comprise a volume exclusion agent; whereby the relatively short nucleic acid and the relatively long nucleic acid are associated with the solid phase; (i) the nucleic acid of the nucleic acid composition comprises relatively short nucleic acid and relatively long nucleic acid, (ii) the relatively short nucleic acid is about 300 base pairs or less, (iii) the relatively long nucleic acid is larger than about 300 base pairs, (iv) the solid phase is a collection of particles, the particles comprise silica, and the solid phase does not comprise a functional group that interacts with the nucleic acid, and (v) the association conditions comprise a chaotropic salt and do not comprise a volume exclusion agent; (b) introducing the solid phase after (a) to dissociation conditions that comprise up to 30% volume exclusion agent and a salt, wherein: (i) the salt comprises an ionic salt and is not a chaotropic salt and wherein the ionic salt is at a concentration of 0.25M to 0.5M, and (ii) the relatively short nucleic acid preferentially dissociates from the solid phase under the dissociation conditions as compared to the relatively long nucleic, thereby yielding dissociated nucleic acid; and (i) the salt comprises an ionic salt and is not a chaotropic salt and wherein the ionic salt is at a concentration of 0.25M to 0.5M, and (ii) the relatively short nucleic acid preferentially dissociates from the solid phase under the dissociation conditions as compared to the relatively long nucleic, thereby yielding dissociated nucleic acid; and (c) separating the dissociated nucleic acid from the solid phase, whereby the relatively short nucleic acid is enriched in the dissociated nucleic acid relative to in the nucleic acid composition.