2. Methodologies for Analysis and Identification of Total Petroleum Hydrocarbons

Analysis of total petroleum hydrocarbons (TPHs) from impacted media involves the collection and preservation of samples followed by extraction, concentration, and clean-up of the sample extract as well as detection and quantification of the petroleum hydrocarbons (PHs). Extraction involves the use of methods such as continuous liquid-liquid extraction, purge and trap extraction, headspace analysis, separatory funnel extraction, solid-phase extraction, accelerated solvent extraction, mechanical shaking, microextraction, Soxhlet extraction, ultrasonic extraction, or supercritical fluid extraction, while the concentration of the extract is executed using the trapping method, Snyder column, Kuderna-Danish concentrator, or nitrogen evaporator. Extract clean-up before analysis is done directly using solid-phase cartridges or indirectly using alumina clean-up, silica gel clean-up, gel permeation clean-up, acid-base partition, and desulfurization technique. The measurement of TPHs in impacted media is most frequently done using gas chromatography (GC) coupled with a flame ionization detector, photoionization detector, or mass spectrometric detection. Other methods of final TPHs determination include infrared spectroscopy, gravimetry, ultraviolet fluorescence spectroscopy, immunoassay, and high-performance liquid chromatography. More importantly, the profile of unresolved complex hydrocarbon mixtures in a TPH-polluted sample is amply characterized and resolved using two-dimensional GC. Of all the analytical methods, ultraviolet fluorescence spectroscopy, gravimetry, and GC are more frequently used to determine TPHs levels in the environment.