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Legislated environmental limits regarding the hydrocarbon content of discharge water from offshore oil and gas are becoming progressively more stringent. This is helping stimulate the development of analytical methods that are both robust and reliable whilst being able to quantify oil in water content at the ppm level of detection. Previously, in Wagner (2016 Meas. Sci. Technol. 27 105501), we showed how such a measurement requirement of total oil content could be met by the application of mobile benchtop NMR. Here, we extend this non-optical measurement platform to enable separate quantification of the aromatic and aliphatic oil content of the discharge water; the aromatic content is of increasing interest on account of its much greater toxicity. Our revised method deploys a two solvent measurement protocol whilst retaining the self-calibration characteristic of the original approach. This new methodology was successfully validated using water contaminated with a variety of aromatic and aliphatic hydrocarbons. The uncertainty related to the NMR measurements was shown to be comparable to that of sample preparation; results were also successfully validated against gas chromatography and infrared measurements.

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