The OPTI-TRAP™ is a bi-directional trap cartridge system which is used individually or in a series for sample concentration and purification. The OPTI-TRAP system features a durable biocompatible trap holder assembly made of either PEEK (capillary configuration) or stainless steel with a PEEK flow path (micro and macro configurations). OPTI-TRAPs feature low back pressure and are loaded and eluted manually with a syringe or on-line when plumbed into the sample injection valve. OPTI-TRAPs include titanium frits for full biocompatibility.