BACKGROUND Petroleum oil is one of the necessary indicators for environmental monitoring, which mainly exists in the form of hydrocarbons. Therefore, infrared spectrophotometry is one of the most reliable methods to determine the total amount of petroleum oil. At present, there are two methods for the determination of petroleum by infrared spectrophotometry, which are the three-wave number correction coefficient method and the non-dispersive single wave number standard curve method. The correction coefficient method has many calculation steps and a heavy workload; the single wave number standard curve method does not specify which wave number to use for calculation or is abandoned due to the limited scope of application.

OBJECTIVES To establish a simple standard curve method for calculating the total amount of petroleum.

METHODS Five kinds of oils were scanned by Fourier transform infrared (FTIR) spectroscopy. The absorbance of the three scanning wavenumbers was arranged and combined to obtain five standard curve methods. After comparing the calculated concentration with the prepared concentration, the standard curve method of the sum of three-wave number absorbance was established.

RESULTS When the proportion of aromatic hydrocarbons was less than 50%, the calculation results of this method were consistent with those of the correction coefficient method. The precision of this method was 5.9%-8.0%, and the recovery rate of standard addition was 76.4%-98.2%, which meets the requirements of China's petroleum pollution determination and environmental standards.

CONCLUSIONS This method expands the application scope of the standard curve method. It is simple and easy to understand and has strong operability. It is a useful supplement to the correction coefficient method.