40ml VOC vials PTFE/silicone septa--glass sample vials. I-Chem. Certified to contain . 50 ppb Total Organic Carbon Standard 40 mL septa vial is clear borosilicate glass with 0.125 in. thick, I-CHEM blue, PTFE/silicone septa in an open-top 24-414 polypropylene cap. The I-CHEM molded-in septa retainer ring holds the septa securely in place without.