Method IP 346

How it Works: A weighed amount of oil (usually 4 grams) is dissolved in cyclohexane, then the resulting solution is extracted twice in succession with DMSO. Saline solution is added to the combined DMSO extracts to precipitate the extracted compounds, which are then back-extracted into cyclohexane. The resulting solution is processed to remove water, then transferred to a tared flask and the cyclohexane is removed by rotary evaporation. The flask is weighed, and the wieght of residue determined by subtraction of the tare weight from the final weight. The resulting value is expressed as the weight-percent of DMSO-extractables.

The endpoint: The endpoint of the IP 346 assay is the weight percent of material extracted from the test material into DMSO.

Interpretation of results: The European Commission has mandated that Method IP 346 be used as the basis for labeling certain petroleum refinery streams for carcinogenic potential. These include all streams in the distillate range*, but generally exclude those derived from the vacuum residuum. The standard requires that oils with PAC contents greater than or equal to 3% (w/w)be labeled as potentially carcinogenic. *Light streams expected to have substantial amounts of material boiling below 300ºC must be "topped off" prior to assay using a prescribed distillation procedure, a service PetroLabs does not currently provide.

Logistics: See Modified Ames Test

Work Product: We conduct Method IP 346 in strict accordance with the procedures described in the Institute of Petroleum publication.