Concentration Quantification of Oil Samples by Three-Dimensional Concentration-Emission Matrix (CEM) Spectroscopy

The isopropanol was chosen as the extracting agent due to its low fluorescence efficiency. 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 ppm, 2.4 ppm, 4.9 ppm, 9.8 ppm, 19.5 ppm, 39 ppm, 78 ppm, 156 ppm, 312 ppm, 625 ppm, respectively) was prepared by diluting the stock solutions. A series of test samples (5 ppm, 100 ppm, 200 ppm, 400 ppm, 600 ppm) was prepared by diluting the stock solutions.