Certified 24-400 PP White Screw Cap with Teflon Septa for TOC Vial. 1. Product Description. Certified Caps are especially for LC-MS solution and GC-MS solution. Blue 9-425 Open Top Ribbed Screw Cap with 9mm Red PTFE/White Silicone Septa 1mm Thick (UltraClean). 100pcs/pk. Blue 9-425 Open Top Ribbed Screw Cap with 9mm Red PTFE/White Silicone