Abstract: Fluid sample purification systems and methods are provided for isolating molecules of interest in a fluid sample. The fluid sample purification system has a housing with a distal end and distal opening adapted for the passage of a fluid and a proximal end and proximal opening adapted for passage of a fluid. A distal retainer is located inside the housing and above the distal opening. A proximal retainer is located inside the housing between the distal retainer and the proximal opening, or is located adjacent to, in contact with, or over the proximal opening. The system also comprises adsorption material, e.g., functionalized particles, inside the housing and confined between the distal retainer and the proximal retainer. The adsorption material adsorbs undesirable material while simultaneously rejecting desirable materials. Methods are also provided for isolating molecules of interest using the fluid sample purification system.