DETERMINATION OF CALCIUM, MAGNESIUM AND ZINC IN UNUSED LUBRICATING OILS BY ATOMIC-ABSORPTION SPECTROSCOPY

Varying concentrations of lanthanum and strontium were added to soluti ons of ashed unused lubricating oils for the determination of calcium, magnesium and zinc content using flame atomic absorption spectrophoto metry. At least 3000 mu g g(-1) of lanthanum or strontium was required to completely overcome the interference of the phosphate ion, PO43-, and give peak values for calcium. The presence of lanthanum or stronti um did not cause an appreciable increase in the amount of magnesium an d zinc obtained from the analyses. The method is fast and reproducible , and the coefficients of variation calculated for the elements using one of the samples were 1.6% for calcium, 3.5% for magnesium and 0.2% for zinc. Results obtained by this method were better than those obtai ned by other methods for the same samples.