The certification of natural matrix environmental standard reference materials (SRMs) at the National Institute of Standards and Technology (NIST) is based on the agreement of results from two or more different analytical techniques. Four different analytical techniques were used for the determination of polycyclic aromatic hydrocarbons (PAHs) in a new marine sediment reference material, SRM 1941a, Organics in Mire Sediment. These procedures were based on reversed-phase liquid chromatography (LC) with fluorescence detection, a multidimensional a procedure, and gas chromatography/ mass spectrometry on to stationary phases with different selectivity for the separation of PAH isomers. The results from these four approaches were in good agreement and were combined to provide certified concentrations for 23 PAHs, which represents the largest number of certified concentrations for PAHs in any natural matrix SRM