The Whatman® Acid Treated Low Metal TCLP Circles manufactured by Whatman International Ltd. are made of binder free borosilicate glass microfiber with a particle retention rating of 0.6 μm to 0.8 μm. Toxicity Characteristic Leaching Procedure (TCLP) is designed for determination of the leaching potential in a landfill for hazardous organic and inorganic contaminants which will threaten drinking water sources by migrating into groundwater.