PAH extracts of commercially available materials can be stored for a long period without a loss of the PAH compounds due to degradation. They, therefore, can be used as quality control samples on a routine basis, e.g., quantitation. PAH concentrations in the sludge were about 1 mg/kg dw.
Sandell, E., Tuominen, J., & Kiviranta, A. (1994). The Stability of polycyclic aromatic hydrocarbons (PAH) in extracts of sewage sludge stored for a period of one year. Polycyclic Aromatic Compounds, 5(1-4), 235-239. https://doi.org/10.1080/10406639408015176