Compound Certified Reference Value Compound Certified Reference Value ng/g ng/gNaphthalene. (35 ± 20) Pentachlorobenzene . 65 ± 8Acenaphthylene . (25 ± 8) Hexachlorobenzene . 279.0 ± 33Acenaphthene. (22 ± 9) Hexachlorobutadiene . 61 ± 7Fluorene . (42 ± 21