The petroleum industry – both offshore and onshore – has regulations that limit the amount of oil in discharged water. Fixed filter infrared (IR) analysers have been used to test oil levels in produced water on drilling platforms for over 45 years for a number of reasons. On oil rigs where real estate is at a premium, infrared analysers such as the Wilks InfraCal TOG/TPH analysers are compact (typically 6in or 15cm², weighing less than 5lbs) and rugged enough to withstand salt air and a rustic lab set up.
The operation can be done by non-technical personnel in less than 15 minutes. Infrared methods also match well with onshore laboratory testing making it a reliable way to keep effluent levels under the regulated amount.
US EPA methods 418.1 and 413.2 were used extensively worldwide until the Montreal Protocol called for Freon (the solvent used in the analysis) to be phased out. Infrared analysis using tetrachloroethylene (perchloroethylene) for the extraction process is still a regulatory method in the North Sea to ensure compliance with discharge permit levels.
As IR was typically used as a quick verification that oil and grease levels were below the regulated level, other solvents such as tetrachloroethylene, hexane, n-pentane or S-316 are now widely used on both offshore and onshore oil platforms even though there is not an associated EPA method for these solvents. There is an ASTM method (D-7066) for infrared oil in water analysis using S-316. Trying to do gas chromatographic or hexane / gravimetric tests on oil drilling platforms is either too time consuming or too complicated. IR is, therefore, used as a daily check with a monthly sample typically going onshore for a regulatory test.