Determination of contaminants in used lubricating oils and in wastewater contamined by these lubricants.

A simple and reliable ashing procedure is proposed for the preparation of used lubricating oil samples for the determination of Zn, Fe, Ph, Ni and Cu by the flame atomic absorption spectrometry technique. Sulpharrilic acid was added to oil samples, the mixture coked and the coke ashed at 550 C-1. The solutions of the ash were analysed by flame AAS for these metals. The quantification limits were 38.250 mu g g(-1) for Zn, 4.550 mu g g(-1) for Fe, 1.562 mu g g(-1) for Pb 1.450 pg g(-1) for Ni, and 0.439 mu g g(-1) for Cu. The determinations, in lubricating oil, showed good precision and accuracy with recoveries between 90 and 110 %, indicating a negligible matrix effect in the experiments using addition of analyte, with relative standard deviation lower than 5%. The results for analysis of wastewater contamined by theses lubricants showed a very high relative standard deviation.