Surfactant interference in turbidity analysis for petroleum in soil samples

To confirm the performance of turbidity analysis (TA) for petroleum in soil samples rind assess false negative risks thereto, surfactant interference effects were investigated on TA. Anionic and nonionic sur-factants were spiked into 2-propanol extracts of petroleum, which were brought in the analytical procedure. The relation between the concentration of surfactants and the turbidity degree or absorbance of the solution resulted when petroleum was salted-out was evaluated. The absorbance value decreased with the concentration of surfactant increased, resulting in occurrence of interference. However, the shapes of working curves remain the same even when surfactants were added. The results support that TA is still robust enough and works as a detection method when applied to samples in the environment where surfactants were controlled not to interfere with the detection.