Quantitative Analysis of Petroleum Oil Pollutants by Infrared Spectrophotometry

The accuracy and sensitivity of infrared spectrophotometry are evaluated for the quantitative analysis of water dispersed oils, by single point analysis. Absorbance versus concentration (Beer-Bouguer Law) plots are prepared for viscous and nonviscous crude and processed oils in Freon 113, carbon tetrachloride, and in a mixture of these solvents. Absorbances at 2930/cm are measured in 10 and 100-mm path length cells, with and without ordinate scale expansion. Solution concentrations in the range 0.5 to 40 mg/100 ml oil in solvent yield linear plots that pass through the origin. The concentration 0.05 mg/100 ml oil in solvent yields a recognizable absorption band at approximately 2930/cm when measured in 100-mm path length cells with ordinate scale expansion X5. This is considered the practical detection limit of these oils by the infrared (IR) technique. Stability of oil absorptivities following solution storage, and use of IR absorptivities for oil identification are also examined briefly.