24mm TOC/VOC EPA vials with screw cap-Voa Vial Supplier . Aijiren’s 24mm Purge and Trap Vials are often used in TOC systems as Vials for storing samples. Usually this kind of Vias is 40ml Screw Neck Vial. 24mm White Screw Closures--Aijiren Vials for HPLC/GC. The 24mm Screw Cap produced by Aijiren is often paired with 24mm Sample Storage Vial.