Because of the need to recover oils used automotiveand industrial lubricants, is of vital importance to takeinto account the initial concentration of contaminantsin oils untreated and treated, to reveal whether theprocesses of recovery or treatment they are subjected,is being well executed, knowing that this is done toreduce contaminants, and then re-used as alternativefuels. The atomic absorption instrumental chemistryis a technique that is used for laboratory analysis inthe quantification of contaminants and in this casewas used spectrophotometer of the Libre Universityto quantify contaminants present in oils before andafter the treatment process for companies Ecolcinand Proptelma.