ASTM D1091-11(2016)

1.1 These test methods cover the determination of phosphorus in unused lubricating oils and lubricating oil additives and their concentrates. The test methods are not restricted with respect to the type of phosphorus compounds that may be present—for example, trivalent or pentavalent phosphorus compounds, phosphines, phosphates, phosphonates, phosphorus sulfides, and so forth—since all are quantitatively converted to an aqueous solution of orthophosphate ion by oxidation of the sample during the course of analysis.