Standard Reference Materials (SRMs) for the determination of polycyclic aromatic compounds - Twenty years of progress

In 1981 the National Bureau of Standards, now the National Institute of Standards and Technology (NIST), issued the first natural matrix Standard Reference Material (SRM) for the determination of polycyclic aromatic compounds (PACs), SRM 1580 Organics in Shale Oil. In the next 10 years, additional natural matrix SRMs were developed including air and diesel particulate matter, petroleum crude oil, coal tar, sediment, and mussel tissue. The SRMs represented the "first generation" of natural matrix SRMs for the determination of PACs. The SRMs had "certified" values for only 5 to 12 PACs; however, their development established the foundation for the implementation of the "two or more independent analytical techniques" approach for certification of individual PACs in environmental matrices. The requirement for use of different analytical techniques spurred the development of both gas chromatography (GC) and liquid chromatography (LC) approaches for the determination of PACs. Since the mid-1990s, the "second generation" of natural matrix SRMs has been issued by NIST with certified values for over 20 PACs in each material. The greater number of certified values in these SRMs was the result of the combination of measurements using reversed-phase LC with fluorescence detection, multidimensional LC, and GC with mass spectrometric detection using two or more stationary phases with different selectivity for polycyclic aromatic hydrocarbon (PAH) separations. This article discusses the significant developments in analytical methods and chromatographic separation of PAHs during the past 20 years that have resulted in the certification of over 25 SRMs, which are now used worldwide for the validation of analytical methods for the measurement of PACs in environmental matrices.