Gas chromatography versus infra-red spectrometry for determination of mineral oil dissolved in water

Abstract The ability to measure the concentration of oil dissolved in water is important for the controlling of drinking water supplies, the establishment of the possible toxicity for all aquatic organisms, and the examination of the efficiency of oil separators. The usual procedure is to measure the infra-red absorbance of the CH3-and CH2-groups after extraction from the water with carbon tetrachloride. Because the low boiling aromatic hydrocarbons are the most acute toxic components and their solubility in water is even better than that of the saturates, it seemed realistic to aim at this fraction. Therefore we compared two different methods, gas chromatography and infra-red spectrometry, for the determination of the hydrocarbon content of aqueous solutions of crude oil and six refinery products. Gas chromatography proved to be the most suitable method to determine the hydrocarbon content of water; besides a more complete total measurement, it yields data about the individual compounds. Infra-red analysis, on the other hand, reveals the occurrence of dissolved polar compounds originating from mineral oil.