Development of an analytical method for determining hindered phenolic antioxidants in exhaust emissions from light-duty vehicles

Özet

Six hindered phenolic antioxidants (HPAs) from emissions of light-duty diesel and gasoline vehicles weredetermined. Vehicles were tested on a dynamometer that conducted a typical city-driving protocol andtheir exhaust samples were collected on filters. A high-performance liquid chromatography coupled withtandem mass spectrometry (HPLC-MS/MS) method was developed for the determination of HPAs in theexhaust samples. Method detection limits reached low ng/m3 in exhaust after optimization of experimentalconditions. Identification and quantification were proven to be reliable for these phenols inlightly-loaded and ambient filter samples. In heavily loaded samples, matrix interferences existed, whichdecreased recoveries of surrogate in both filter and disk. However, matrix spike samples showed goodrecoveries of target HPAs. In vehicle emission samples, the highest level of HPAs was 2,6-di-tert-butylphenolat 52.7 ng/m3 (28.9 pg/mm2 on filter) in emission of a 2009 Volkswagen Jetta with a dieselengine. Most HPAs were not detected or near detection limits. Therefore, the additives of phenol antioxidantsin fuels were mostly oxidized during the combustion process. Further, the 2009 diesel Jettaproduced about 7 times more of HPAs than the 2008 Pontiac G5 with a gasoline engine. In addition, it isdiscovered that engines operated at a colder ambient temperature (7 C) yielded more HPA emissionsthan at the warmer condition (25 C), because the combustion efficiency of engines are normally reducedat a lower temperature