Anyone involved in field analysis of oil in water will continually get the question 'Does your equipment match the regulatory method?' While the amount of oil in water is highly regulated, it can also be a challenging measurement.
It is complicated by the fact that oil comes in many forms and the measurement is defined by the particular regulatory method. When EPA 1664 is the regulatory method, the 'oil' is anything that is extracted into hexane and remains after the hexane has been evaporated and shows up as weight.
In regions where infrared analysis is the defining method, the 'oil' is whatever is extracted into the solvent and has carbon-hydrogen bonds that absorb infrared light at a specific frequency.
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