Optimisation and assessment of a method for determination of trace metals in used industrial oils

The selection of a method for the determination;of trace metals in used ind ustrial oils led to the use of graphite furnace atomic absorption spectrome try (GF-AAS) as the best technique for sample decomposition/atomisation/det ection. After this step, the instrumental variables were studied with speci al emphasis on optimising the type of diluent used as function of both the physical characteristics of the sample and the concentration of the analyte s to the GF-AAS instrument. A key aspect of the method was the type of stan dard (organic or inorganic solutions) used for calibration which yielded ve ry different metal concentrations for the same samples. The use of a certif ied reference material (NIST CRM 1084(a)) enabled to assess organic solutio ns of metal as the best for calibration. Then, the method thus validated wa s applied to different used Industrial oils.