(Equivalent Test Methods: IP 308 and DIN 51391 T1)
TEST SUMMARY
This test method is applicable for the determination of mass percent barium from 0.005 to 1.0 %, zinc, calcium, and magnesium from 0.002 to 0.3 % in lubricating oils. Higher concentrations can be determined by appropriate dilution. Levels at 100 ppm concentrations are also allowed to be analyzed.
A sample is weighed and base oil is added to 0.25 g total weight. Fifty mL of a kerosene solution, containing potassium as an ionization suppressant, are added, and the sample and oil are dissolved. Standards are similarly prepared, always adding oil if necessary to yield a total weight of 0.25 g. These solutions are burned in the flame of an atomic absorption spectrophotometer. An acetylene/nitrous oxide flame is used.
The presence of certain viscosity improvers (VI) may cause a negative bias for some metals. It is suggested to (a) add the same VI to both the sample and calibration standard, or more easily (b) dilute the VI containing the sample until the VI effect is no longer significant.
TEST PRECISION
Where X is the average of duplicate results.