Determination of Polycyclic Aromatic Hydrocarbons (PAH) in Extender Oils, 08-R8026

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Principal Investigator
Joseph C. Pan

Inclusive Dates:  01/01/09 – 07/01/10

Background - Starting January 1, 2011, the European Union requires all extender oils going into tires have the total content of 8 specific PAH be less than 10 ppm and benzo(a)pyrene be less than 1.0 ppm. However, the method specified by the EU Directive (1999/45/EC) for the analysis of PAHs in oils was IP346, a pass/fail method, which does not produce specific concentration data for the EU-specified 8 PAHs. An analytical method that would accurately and precisely determine PAH concentrations in extender oils was badly needed. The EU targeted 8 PAHs were benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(j)fluoranthene, benzo(k)fluoranthene, benzo(e)pyrene, benzo(a)pyrene, and dibenz(a,h)anthracene.

Approach - This project accomplished the following:

  • Studied the partition coefficients (PC) of PAHs in "polar"-"non-polar" organic solvent systems. The polar solvents tested included N,N'-dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP), dimethyl sulfoxide (DMSO), and furfural. Water (5 percent to 20 percent) was added to some of the polar solvents. The non-polar solvents included pentane, hexane, and cyclohexane.

  • Studied the elution pattern of PAHs on silica gel-, alumina-, and Florisil®-packed liquid chromatographic columns.

  • Applied deuterated PAHs as internal standards to develop an "isotope dilution technique" (ITD) for PAH analysis on oils using a GC/MS.

  • Used proprietary GC columns to resolve PAHs and interfering compounds from oils.

Accomplishments -  Project results were as follows:

  • Found two "polar"-"non-polar" organic solvent systems that successfully extracted PAHs from oils.

  • Found two adsorbents that separate PAHs from oils using liquid chromatographic technique.

  • The developed "isotope dilution technique" rendered precise (percent RSD < 5 percent) and accurate (accuracy >95 percent) PAH determination in oils using GC/MS.

  • The selected proprietary GC columns greatly reduced interference on chrysene and benzo(a)pyrene determinations in oils.

  • The developed ITD-GC/MS method was successfully expanded from 8 to 16 PAHs in oils and other matrices.

  • The developed PAH method works well on oil, asphalt, carbon black, and rubber samples.

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