2018/01/01 · 60?mL glass vials (EPA, VWR, ref: 548-0156) and screw white caps in polypropylene and polytetrafluoroethylene (PTFE, VWR, ref: 548-0871). Half of the bottles should be labeled as filtered, the other half as unfiltered. • 250?mL amber borosilicate bottles (Boston Round Glass Bottles, Unlined, Standard, Thomas Scientific, ref: D0154-8).