Hundreds of different hydrocarbon compounds derived from agricultural, industrial and domestic practices are released daily into aquatic systems with adverse effects in the desirable potable characteristics, in aquatic fauna and flora, and on tourism, recreation and aesthetics of the impacted areas. Total petroleum hydrocarbon concentration data cannot be used to quantitatively estimate human health risk, but can be used as an important tool for three purposes: verifying if there is a problem, assessing the severity of the contamination and following the progress of a remediation effort. The objective of this work was the optimization of the experimental conditions for the determination of total hydrocarbons in water by liquid-liquid extraction coupled to infrared spectrophotometry, with the goal of improving the qualitative information provided by the spectra. The method was validated with satisfactory detection and quantification limits and demonstrated acceptable levels of precision, accuracy and analyte recoveries. Solid phase extraction and microwave assisted extraction procedures were tested and compared to the liquid extraction. Additionally, a spectra library was prepared with different natural and synthetic oils. The developed method was applied to the analysis of Portuguese inland and coastal bathing waters and wastewaters and their compliance with national and European legislation was assessed. (C) 2011 Elsevier B.V. All rights reserved.