− | ''Porphyrins'' in crude oil are large, complex molecules derived primarily from [[chlorophyll]] and related compounds. They are found in virtually all oils and rock extracts, with the exception of [[condensate]]s that have lost their heavy ends. Porphyrins are separated by HPLC and can be analyzed by several different methods. | + | ''Porphyrins'' in [[crude oil]] are large, complex molecules derived primarily from [[chlorophyll]] and related compounds. They are found in virtually all oils and rock extracts, with the exception of [[condensate]]s that have lost their heavy ends. Porphyrins are separated by HPLC and can be analyzed by several different methods. |