Determination of wear metals in engine oils by atomic absorption spectrometry with a graphite rod atomizer

Abstract

The concentrations of Ag, Cr, Cu, Fe, Ni, Pb, and Sn in used jet-engine and reciprocating-engine oils have been determined by atomic absorption, using atomization from a cavity in a heated graphite rod. The samples analyzed were taken from those provided by the United States Air Force Spectrochemical Oil Analysis Program (S.O.A.P.) during the period May 1969-December 1971. This enabled a comparison to be made between the present results and those obtained by flame atomic absorption by the laboratories participating in S.O.A.P. Excellent agreement between the two sets of results was found for Ag, Cu, Fe, Ni, and Pb. The use of the graphite-rod atomizer led to results for Cr that are considerably higher than those found with an air-acetylene flame, but are comparable with results obtained with a nitrous oxide-acetylene flame. It appears that most of the Sn concentrations are near, or below, the levels detectable with flame atomization, and in some cases Sn was also undetectable with the graphite-rod atomizer.Application of trace element analysis to the determination of wear-metal particles suspended in the lubricating oils of railroad and aircraft engines has been firmly established for many years. Early methods of analysis included colorimetry (after ashing and dissolution of the sample) (7), and a number of direct emission spectrographic techniques, discussed by Fry (2). Direct-reading emission spectrographs continue to be widely used. The past decade has seen the development of flame atomic absorption spectrometry (3-10) and preliminary investigations of flame atomic fluorescence spectrometry (77, 12). The range of applications of engineoil analysis for wear metals has been reviewed by Middledorf (13).Attention has recently been given to the possible advantages of using flameless atomization systems for oil analysis

The determination of trace metals in lubricating oils by atomic spectrometry

“…Early studies of the use of ETAAS did not employ the modern STPF concept, using instead graphite rods or atomization directly from the wall of the graphite tube, with no care taken regarding chemical modification and background correction [6,[46][47][48][49][50]. The possibility of using controlled thermal conditions for atomization was identified as potentially helpful for the analysis of oils.…”

“…The possibility of using controlled thermal conditions for atomization was identified as potentially helpful for the analysis of oils. Nonreproducible results are reported for the more refractory elements, such as Cr [47]. Modern ETAAS is based on the SPTF concept, which has brought about important improvements in terms of selectivity and sensitivity.…”

Determination of Refractory Elements in Used Lubricating Oil by ICPOES Employing Emulsified Sample Introduction and Calibration with Inorganic Standards

“…Electrothermal atomic absorption spectrometry (ET AAS) has been one of the techniques of choice, since it tolerates samples of high organic load and, in general, allows good sensitivities to be achieved. 2,[4][5][6][7][8] In the case of refractory elements, which can be related to the wearing of specific parts of engines and turbines, 9 AAS methods are not suitable, since those elements have high boiling points and/or tend to form high melting-point carbides and oxides, leading to low sensitivities. 10 For refractory metals, better limits of detection can be obtained using ICPOES because of the efficient atomization, ionization and excitation achieved in the ICP.…”

Comparative study of electrothermal atomic absorption spectrometric methods for the determination of silver in used lubricating oils

“…Although electrothermal atomic absorption spectrometry offers excellent sensitivity for silver, a limited number of methods based on this technique are described in the literature for the determination of silver in used lubricating oil. 4,15,16 Two of them, instead of using tube atomizers and the stabilized platform temperature furnace (SPTF) concept, employed outdated graphite rod or graphite filament atomizers. 15,16 Samples with high organic load containing small size suspended metal particulate can be efficiently managed by ETAAS.…”

“…4,15,16 Two of them, instead of using tube atomizers and the stabilized platform temperature furnace (SPTF) concept, employed outdated graphite rod or graphite filament atomizers. 15,16 Samples with high organic load containing small size suspended metal particulate can be efficiently managed by ETAAS. This feature makes sample preparation considerably simpler and can also allow calibration against analyte aqueous standards.…”