Wear elements in engine oil; Indirect ablation laser induced breakdown spectroscopy; Matrix effect; Calibration curves;LUBRICATING OILS; CRUDE-OIL; QUANTITATIVE-DETERMINATION; MASS-SPECTROMETRY; METALS

Engine oil plays an important role in the engine operation. Elements composition and concentration in engine oil will be changed as the engine operates, which can lead to the deterioration of engine oil, and the engine thereby will be worse. A rapid and effective detection approach for oil performance, therefore, is proposed to prevent further deterioration. Indirect ablation laser induced breakdown spectroscopy (IA-LIES) is a new technology introduced specially for oil samples, which focuses on the indirect ablation of oil samples by metallic plasma with high temperature, improving the detection sensitivity and stability. In this paper, the matrix effect on calibration curves of analytical elements (Mg, Fe and Ni) in different oils was investigated. The results show that the matrix effect is quite small and reasonably negligible. A universal calibration curve can be established for analytical metals in different types of oil, and the linear fitting coefficients are all superior to 0. 99. We used the universal calibration curves to determine the concentrations of Mg, Fe and Ni in mixed oils. The IA-LIES results show a good agreement between the measured and known values. The IA-LIBS is further improved and can promote the detection of engine oil performance, which has important scientific significance for the diagnosis of engine wear.