A comparison study of gravimetric and ultraviolet fluorescence methods for the analysis of total petroleum hydrocarbons in surface water

Abstract

Petroleum hydrocarbons are important environmental contaminants and determination of petroleum-derived hydrocarbons are significant. The definition of total petroleum hydrocarbons depends on the analytical method used as no single method detects the entire range of petroleum-derived hydrocarbons. Two analytical methods have been used in this study for the analysis of aqueous samples for total petroleum hydrocarbons. EPA has approved Method 1664A as a standard testing procedure for the analysis of Total Petroleum Hydrocarbons in water. This study compares the EPA Method 1664A and Ultraviolet Fluorescence Technology for the analysis of total petroleum hydrocarbons in aqueous matrix. The study compared the results of the analysis of surface water samples and artificial samples made from 1,2 diphenylbenzene (o-terphenyl) and stearic acid, o-terphenyl, 1,4 diphenylbenzene (p-terphenyl), Formula Shell 10W-30 Motor Oil and No.6 Fuel Oil. The results are found to be comparable for the surface water samples over the reportable range of both the analytical methods. It is observed that the o-terphenyl standards show weak fluorescence at low concentrations and the light emission property decreases with increase of concentration at the wavelength used in the fluorometer. The Formula Shell 10W-30 Motor oil has shown a feeble response towards the ultraviolet excitation of the samples in inert solvents. Ultraviolet excitation of No.6 fuel oil and p-terphenyl has recorded 5 and 100 times fluorescence on comparison with the TPH-Oil calibration standards. As the optical experiments indicate that the fluorescence property of hydrocarbons and oils vary significantly, standards used for calibrating the instrument should be site and type specific.