The soil and groundwater clean-up requirements for polycyclic aromatic hydrocarbons (PAHs) are typically set at the reporting limits defined by the conventional full scan 8270C method. Interferences such as DRO and/or HRO contamination can present a significant challenge resulting in sample dilutions. The 8270C method allows laboratories to quantitate semi-volatile compounds using selected ion monitoring (SIM). By highlighting specific ions in the mass spectum rather than full scan, this technique provides a significant (50-100x) increase in sensitivity. Extracts with background interferences can be diluted and analyzed by SIM while still maintaining mandated reporting limits. CAS routinely provides SIM for PAH’s when the need arises.