Sampling artifact estimates for alkanes, hopanes, and aliphatic carboxylic acids

Sampling artifacts for molecular markers from organic speciation of particulate matter were investigated by analyzing forty-one samples collected in Philadelphia as a part of the Northeast Oxidant and Particulate Study (NEOPS). Samples were collected using a high volume sampler with two quartz fiber filters in series. n-Alkanes (C23–C31), hopanes (C27–C31), and n-alkanoic acids (C10–C22) were analyzed by gas chromatography-mass spectrometry (GCMS). The extent of artifact error was dependent on vapor pressure and species concentration. Particulate organic species are classified into the following three categories: (1) the amount collected on the backup filter was often a large fraction of the amount collected on the front filters (n-alkanes C23 and C24, n-carboxylic acids C10–C14); (2) the amount collected on the backup filter was consistently a small fraction of the amount collected on the front filter (n-alkanes C25–C28, hopanes C27–C30, n-carboxylic acids C15–C18, and dicarboxylic acids C3–C9); (3) the species was rarely observed on backup filters (n-alkanes C29–C31, hopanes C31 and C32).