Detection of oil–water interface based on laser-induced breakdown spectroscopy

Abstract Oil leakages can result in significant environmental pollution, and effective methods for separating oil and water must be developed. During this process, being able to accurately determine the interface between oil and water is particularly important. In this study, laser-induced breakdown spectroscopy (LIBS) was used to detect the luminescence spectra of oil and water with the aim of accurately determining the oil–water interface. The underlying principle exploited in this work is that the constituent elements of oil and water are different and hence will exhibit different characteristic peaks. Thus, based on these peaks, the position of the interface can be determined. More specifically, one can determine whether the oil and water have been separated completely based on the presence (or absence) of the characteristic peak of the elemental C in the oil. In addition, based on the ratio of the intensities of the C and H peaks in the LIBS spectrum, the thickness of the oil layer below the breakdown depth can be determined. What’s more, it is considerable to detect the thickness of the upper-layer liquid between two organic liquids or one with water which are immiscible in breaker, through the same way as analysing the effects of the oil–water interface spectroscopy detection.