Effect of laser wavelength on the quantitative analysis performance of indirect ablation LIBS for analyzing the metals in lubricating oil

Abstract

For monitoring the lubricant quality and engine wear status, indirect ablation laser-induced breakdown spectroscopy (LIBS) was introduced to determine the metal elements in lubricating oil. Due to the different transmittance values of oil at different laser wavelengths, the effect of the laser wavelength on the detection performance of indirect ablation LIBS was studied. Under optimal parameters, the calibration curves were established for 10 metal elements with laser wavelengths of 1064, 532, and 355 nm. The obtained results show the average limit of detection (LoD) and the average relative standard deviation (ARSD) of spectral intensity for 1064, 532, and 355 nm are 15.942, 56.804, and 25.077 mg L⁻¹, and 2.874%, 9.253%, and 12.649%, respectively. In addition, the average R², the average relative error (ARE), and the root mean square error of cross validation (RMSECV) for a laser wavelength of 1064 nm are 0.991, 9.045%, and 18.379 mg L⁻¹, which are better than those at 532 nm and 355 nm. Therefore, the laser wavelength affects the quantitative analysis performance of indirect ablation LIBS for the analysis of metal elements in lubricating oil and the optimal wavelength is 1064 nm.