A mass spectrometry method could improve the way oil-processing facilities detect seawater contaminated with low levels of oil (Anal. Chem., DOI: 10.1021/ac2008042). Many national governments regulate the oil concentration of water discharged from these facilities. Stephen Taylor, of the University of Liverpool, in England, and his colleagues sought to improve on the accuracy and sensitivity provided by conventional oil measurement techniques such as ultraviolet fluorescence and infrared spectroscopy by using membrane inlet mass spectrometry (MIMS), which can distinguish various types of oil. Rarely used for field testing, MIMS relies on a membrane to block water and other polar molecules from entering the mass spectrometer, while allowing hydrophobic compounds such as oil to pass through for detection. At an oil-processing facility in Scotland, the researchers measured concentrations of crude oil as low as 15 mg/L, which is half the discharge limit in the U.K. They also could differentiate between two types of crude oil, API 35 and API 36, based on hydrocarbon composition. Taylor plans to couple a portable MIMS instrument with existing oil-in-water monitors to complement their ability to measure oil concentrations quickly.