Concentration-Emission Matrix (CEM) Spectroscopy Combined with GA-SVM: An Analytical Method to Recognize Oil Species in Marine

Samples PreparationSix different types of oils: 0#diesel, crude oil, heavy oil, 92#gasoline, shell helix 10w-40, and motor oil 20w-40. The oil sample was weighted by electronic balance and dissolved in isopropanol, which was placed in an ultrasonic oscillator to be fully dissolved. After waiting for 30 min, the supernatant was taken as the stock solution with a concentration of 5000 ppm of the oil sample. The concentrations of working solutions with a serial of concentrations (1.2, 2.4, 4.9, 9.8, 19.5, 39, 78, 156, 312, 625 ppm, respectively) were prepared by diluting the stock solutions.The three-dimensional concentration-emission matrix (CEM) has been formed by obtaining the fluorescence emission spectra at the excitation wavelength of 266 nm with 10 series of concentrations. The emission spectrum of each concentration of oil is a matrix with 146 rows and 1 column, so the CEM composed of 10 concentrations of emission spectra is a matrix with 146 rows and 10 columns.