The simultaneous determination of 15 different wear metals in lubricating oil by inductively-coupled plasma-atomic emission spectrometry is described. An aerosol formed from a solution of the lubricating oil in 4-methyl-2-pentanone is injected into the axial channel of an inductiveiy-coupied plasma where the atomic spectra are excited. Detection limits range 0.0004 to 0.3 ppm for the elements studied. Low and high viscosity oils (nominally 1.9 X to 2.45 X m2/s, respectively) can be accommodated without biasing the analytical results. Approximately 1.5 min are required for completing the analyticai cycle for one sample. Relevant data on precision and accuracy are included.

The design and performance of two devices for selective spectral modulation in flame emission and atomic absorption spectrometry are reported. The similar techniques use periodic piezoelectrically induced deformation of one or two fluidic channels to the solution nebulizer. The mechanically simpler channel device generates a regular ac ripple on the solution flow into the flame. In certain situations, the influence of the solvent pulsing on the flame temperature permits the differentiation of flame background signals from signals of analytical interest; alternatively, advantage can be taken of mutually compensating flame processes which negate the influence of solvent modulation on the flame background. In the generally applicable dual channel technique, the nominal solution uptake rate is constant and the ac components in the flame spectra represent the differences in chemical composition between the analytical and the blank solutions. Effective background discrimination ratios for certain band systems exceed 103:1.

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