prepare HPLC glass vials bonded PTFE/silicone slit septa The HPLC test Waters recommends pre-slit PTFE/silicone septa, for venting and accurate sample draw. VWR® Autosampler Vials, Inserts and Closures. 2mL, 12x32mm, 8mm Standard Opening Screw Thread Vials and Inserts Lot-tested including HPLC and GC analysis for 9 critical parameter.