Whatman ® Spartan ® HPLC Certified Syringe Filters, Diam. 13 mm, Regenerated Cellulose, 0.2 μm, with Mini-Tip Outlet, 500/pk, Whatman International Ltd. (CAT#: STEM-L-4933-LC) Millex Syringe Filter, Hydrophilic PTFE, Non-Sterile, 0.45 µm Pore Size, 13 mm Diam., Merck KGaA, Darmstadt, Germany (CAT#: STEM-L-6782-LC)