Publications by authors named "Trifa Ahmed"

An online two-dimensional (2D) liquid chromatography/2D gas chromatography system with two mass-selective detectors has been developed on the basis of a previous system with two flame ionization detectors. The method translation involved the change of carrier gas from hydrogen to helium, column dimension and detectors. The 2D system with two mass-selective detectors was validated with use of polycyclic aromatic hydrocarbon (PAH) standards and two standard reference materials from air and diesel exhaust.

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Background: Polycyclic aromatic hydrocarbons (PAHs) are the main toxic compounds in natural bitumen, a fossil material used by modern and ancient societies around the world. The adverse health effects of PAHs on modern humans are well established, but their health impacts on past populations are unclear. It has previously been suggested that a prehistoric health decline among the native people living on the California Channel Islands may have been related to PAH exposure.

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The objective of this study was to develop a novel analytical chemistry method, comprised of a coupled high-performance liquid chromatography-gas chromatography/mass spectrometry system (LC-GC/MS) with low detection limits and high selectivity, for the identification and determination of oxygenated polycyclic aromatic hydrocarbons (OPAHs) and polycyclic aromatic hydrocarbons (PAHs) in urban air and diesel particulate matter. The linear range of the four OPAHs, which include 9,10-anthraquinone, 4H-cyclopenta[def]phenanthrene-4-one, benzanthrone, and 7,12-benz[a]anthraquinone, was 0.7 pg-43.

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A multidimensional, on-line coupled liquid chromatographic/gas chromatographic system was developed for the quantification of polycyclic aromatic hydrocarbons (PAHs). A two-dimensional liquid chromatographic system (2D-liquid chromatography (LC)), with three columns having different selectivities, was connected on-line to a two-dimensional gas chromatographic system (2D-gas chromatography (GC)). Samples were cleaned up by combining normal elution and column back-flush of the LC columns to selectively remove matrix constituents and isolate well-defined, PAH enriched fractions.

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The efficiency of extraction of polycyclic aromatic hydrocarbons (PAHs) with molecular masses of 252, 276, 278, 300, and 302 Da from standard reference material diesel particulate matter (SRM 2975) has been investigated using accelerated solvent extraction (ASE) with dichloromethane, toluene, methanol, and mixtures of toluene and methanol. Extraction of SRM 2975 using toluene/methanol (9:1, v/v) at maximum instrumental settings (200 °C, 20.7 MPa, and five extraction cycles) with 30-min extraction times resulted in the following elevations of the measured concentration when compared with the certified and reference concentrations reported by the National Institute of Standards and Technology (NIST): benzo[b]fluoranthene, 46%; benzo[k]fluoranthene, 137%; benzo[e]pyrene, 103%; benzo[a]pyrene, 1,570%; perylene, 37%; indeno[1,2,3-cd]pyrene, 41%; benzo[ghi]perylene, 163%; and coronene, 361%.

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