The American Society for Testing and Materials (ASTM) sets the industry standardized test methods for determining among other things additive elements, wear metals, and contaminates in lubricating oils. In this case, the ASTM D5185 otherwise known as Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) is where zinc and phosphorous content is commonly tested and reported by the industry.

To read the ASTM test methodology for (ICP-AES), click on the ASTM D5185 link – HERE