Method Development for Accurate Determination of Eight Polycyclic Aromatic Hydrocarbons in Extruded High-impact Polystyrene

An analytical method was developed for the accurate determination of eight polycyclic aromatic hydrocarbons (PAHs) in extruded high-impact polystyrene (HIPS) as a higher-order reference method. Uncleaned HIPS matrix rendered the accurate quantitation impossible and hampered the repeatability of the gas chromatography/mass spectrometry (GC/MS) measurement. This led to a bias in the results and increased the measurement uncertainty. Extracts were sufficiently purified through a two-step process: (i) dissolution and precipitation and (ii) molecularly imprinted polymers-solid phase extraction for clean-up. Co-elution of indeno(1,2,3-cd)pyrene (IP), dibenz(a,h)anthracene (DBahA), and their C-labeled isotopes resulted in a bias in the area ratios of IP/C-IP and DBahA/C-DBahA, thus increasing the measurement uncertainty. An optimized GC condition using an Rxi-PAH column improved the peak separation of IP and DBahA and their isotopes, thus improving the quality of the measurement. The optimized method was validated using PAH (0.36-0.45 mg/kg)-containing HIPS pellets. The optimized method had excellent repeatability (<2%) and reproducibility (<3%) for concentrations less than 0.5 mg/kg of the eight PAHs in HIPS. Using the optimized method, the relative expanded uncertainties for all the target PAHs were below 5% (with a 95% level of confidence).