A system for separating an aqueous stream of mixed polynucleotides into a series of length-based polynucleotide fractions and collecting one or more of the length-based polynucleotide fractions into separate containers. greater than the melting point of the polymer or in the case of perfluoropolymer, at a temperature of at least 450\xb0 C. The barrel has a firing axis and includes a threaded end opposite the muzzle end and defines a recess formed adjacent the muzzle end.