Bruce A. Benner

Distinguishing the Contributions of Residential Wood Combustion and Mobile Source Emissions Using Relative Concentrations of Dimethylphenanthrene Isomers

As part of the United States Environmental Protection Agencys Integrated Air Cancer Project, air particulate matter samples collected in Boise, ID, were analyzed by gas chromatography with mass spectrometric detection (GC-MS) and apportioned between their two main sources : residential wood combustion (RWC) and motor vehicle (MV) emissions. The technique used for distinguishing the source contributions involved comparison of the concentration of 1,7-dimethylphenanthrene (1,7-DMP), a polycyclic aromatic hydrocarbon (PAH) emitted primarily by burning soft woods (e.g., pines), with that of a PAH emitted in modest concentrations by both RWC and MV sources, 2,6-dimethylphenanthrene (2,6-DMP). These results were then compared with the mean 1,7-DMP/2,6-DMP ratio of 48 samples collected in a roadway tunnel, with any enrichment in the Boise sample ratios over the mean tunnel ratio attributable to the RWC source. These resulting RWC contributions were compared with fraction RWC results obtained by radiocarbon measurements ( 14 C/ 13 C) of the same extracts from Boise, with generally good correlations between the two techniques observed, suggesting that the methods are comparable when used to distinguish emissions of MVs from RWC of soft woods.

Comparison of supercritical fluid extraction and Soxhlet extraction for the determination of polychlorinated biphenyls in environmental matrix standard reference materials

Supercritical fluid extraction (SFE) was compared to traditional Soxhlet extraction for the determination of polychlorinated biphenyl congeners in three standard reference materials: SRM 1941a (Organics in Marine Sediment), SRM 1944 (New York/New Jersey Waterway Sediment) and SRM 2974 [Organics in Mussel Tissue (Mytilus edulis) (Freeze-Dried)]. The concentrations determined using SFE compared well with the certified concentrations for the majority of the polychlorinated biphenyl congeners.

Summarizing the effectiveness of supercritical fluid extraction of polycyclic aromatic hydrocarbons from natural matrix environmental samples.

A summary of the supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons (PAHs) from four natural matrix Standard Reference Materials (SRMs) is presented. The work involved the investigation of the effects of extraction fluid [carbon dioxide (CO(2)), chlorodifluoromethane (R22), and 1,1,1,2-tetrafluoroethane (HFC134a)], fluid modifier (dichloromethane and aniline), temperature (60, 150, and 200 °C) and added water on the SFE recoveries of PAHs compared to certified results from Soxhlet extractions. For SRM 1649a (Urban Dust/Organics), R22 yielded excellent recoveries (>90% of certified concentrations) of all PAHs measured, while results for the same SRM using HFC134a as the fluid were typically <80% of the certified concentrations for most of the PAHs measured. For SRM 1941a and 1944, both aquatic sediments with similar physical and chemical compositions, extractions of the wet materials with dichloromethane-modified CO(2) (10%, v/v) yielded quantitative recoveries of all PAHs for SRM 1944 but an obvious trend of lower recoveries for higher molecular weight PAHs (≥228 amu) for SRM 1941a. Results of SFEs of SRM 1650 (Diesel Particulate Matter) showed that this material is the most refractory of the SRMs investigated in this study, with recoveries of indeno[1,2,3-cd]pyrene and benzo[ghi]perylene at <20% of the Soxhlet results.

Radiocarbon “dating” of individual chemical compounds in atmospheric aerosol: First results comparing direct isotopic and multivariate statistical apportionment of specific polycyclic aromatic hydrocarbons

Abstract Recent instrumental developments which allow radiocarbon (14C) determinations on microgram quantities of organic material have revolutionized our ability to apportion fossil and biogenic sources of trace carbonaceous gases and aerosols in the environment. The chemical complexity of carbonaceous aerosol, however, presents a challenge in the interpretation of its average isotopic composition. For this reason, there has long been an interest in radiocarbon measurements of specific classes of compounds, or even individual trace compounds of particular environmental concern, such as the polycyclic aromatic hydrocarbons (PAHs). The PAHs hold special interest because they are produced at trace levels in combustion processes; they exhibit compound-specific genotoxicity; and they have the potential to serve as “molecular markers” or tracers for specific ambient aerosol sources. Prior to the work reported here, inferences from ambient studies concerning molecular tracer capabilities have been indirect, relying on circumstantial evidence and/or multivariate statistical techniques. In the present study we demonstrate, for the first time, the ability to measure the 14C content of individual, trace organic compounds (PAHs) in atmospheric aerosol. The research utilized a special, well characterized atmospheric reference material, where individual PAHs were radiocarbon “dated” using off-line gas chromatography/accelerator mass spectrometry (GC/AMS). Separation of individual compounds in sufficient amounts for AMS was accomplished by automated preparative capillary gas chromatography (PCGC). Results showed the PAHs dated to be primarily fossil in origin, and lent support to an earlier multivariate statistical study suggesting that benzo[ghi]perylene might serve as a useful tracer for soot generated by motor vehicles, although this assessment must be viewed as tentative because of potential interference from other compounds incompletely removed from the purified PAH fraction.

Application of Inkjet Printing Technology to Produce Test Materials of 1,3,5-Trinitro-1,3,5 Triazcyclohexane for Trace Explosive Analysis

The feasibility of the use of piezoelectric drop-on-demand inkjet printing to prepare test materials for trace explosive analysis is demonstrated. RDX (1,3,5-trinitro-1,3,5 triazcyclohexane) was formulated into inkjet printable solutions and jetted onto substrates suitable for calibration of the ion mobility spectrometry (IMS) instruments currently deployed worldwide for contraband screening. Gravimetric analysis, gas chromatography/mass spectrometry (GC/MS), and ultraviolet-visible (UV-vis) absorption spectroscopy were used to verify inkjet printer solution concentrations and the quantity of explosive dispensed onto test materials. Reproducibility of the inkjet printing process for mass deposition of the explosive RDX (1,3,5-trinitro-1,3,5 triazcyclohexane) was determined to be better than 2% for a single day of printing and better than 3% day-to-day.

Comparison of methods for extraction of flavanones and xanthones from the root bark of the osage orange tree using liquid chromatography

Abstract This study compares conventional solid–liquid extraction, supercritical fluid extraction (SFE), and pressurized fluid extraction (PFE) for their efficiency in extracting xanthones and flavanones from the root bark of the osage orange tree (Maclura pomifera). Seven compounds were extracted from the plant material by solvent extraction at room temperature for 48 h. The same compounds were removed from the root bark by 45- and 35-min extractions using SFE and PFE, respectively, and under optimized conditions, in same or higher yields than those obtained by the conventional 48-h solvent extraction. Although all seven compounds were present in the SFE extracts when only CO2 was used as the fluid, the addition of 20 vol.% methanol (MeOH) to the CO2 proved essential for achieving high yields. Use of SFE with CO2–MeOH also led to the recovery of an additional flavanone from a wet sample of root bark. This flavanone is absent from the conventional solvent extracts and appears in small amounts in the PFE extracts. An optimized LC separation for the analysis of the different extracts is presented, and it is demonstrated that the separation of xanthones and flavanones is considerably improved by the use of deactivated C18 columns in conjunction with a mobile phase containing acetonitrile and a weak organic acid.

Certification of standard reference material (SRM) 1941a, organics in marine sediment

SRM 1941a, Organics in Marine Sediment, has been recently issued with certified concentrations for 23 polycyclic aromatic hydrocarbons, 21 polychlorinated biphenyl congeners, 6 chlorinated pesticides, and sulfur. Noncertified concentrations have been also reported for additional PAHs, PCB congeners, and chlorinated pesticides and for percent total organic carbon (TOC), aliphatic hydrocarbons, and trace elements. SRM 1941a is the most extensively characterized natural matrix SRM issued by the National Institute of Standards and Technology (NIST).

Development of urine standard reference materials for metabolites of organic chemicals including polycyclic aromatic hydrocarbons, phthalates, phenols, parabens, and volatile organic compounds

AbstractTwo new Standard Reference Materials (SRMs), SRM 3672 Organic Contaminants in Smokers’ Urine (Frozen) and SRM 3673 Organic Contaminants in Non-Smokers’ Urine (Frozen), have been developed in support of studies for assessment of human exposure to select organic environmental contaminants. Collaborations among three organizations resulted in certified values for 11 hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) and reference values for 11 phthalate metabolites, 8 environmental phenols and parabens, and 24 volatile organic compound (VOC) metabolites. Reference values are also available for creatinine and the free forms of caffeine, theobromine, ibuprofen, nicotine, cotinine, and 3-hydroxycotinine. These are the first urine Certified Reference Materials characterized for metabolites of organic environmental contaminants. Noteworthy, the mass fractions of the environmental organic contaminants in the two SRMs are within the ranges reported in population survey studies such as the National Health and Nutrition Examination Survey (NHANES) and the Canadian Health Measures Survey (CHMS). These SRMs will be useful as quality control samples for ensuring compatibility of results among population survey studies and will fill a void to assess the accuracy of analytical methods used in studies monitoring human exposure to these organic environmental contaminants. Graphical AbstractMetabolites of PAHs, Phthalates, Phenols, Parabens, and VOCs in Urine SRMs

Characterization of Composition C4 Explosives using Time-of-Flight Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy

The application of surface analytical techniques such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) is explored as a means of differentiating between composition C4 plastic explosives (C-4). Three different C-4 samples including U.S. military grade C-4, commercial C-4 (also from the United States), and C-4 from England (PE-4) were obtained and analyzed using both ToF-SIMS and XPS. ToF-SIMS was able to successfully discriminate between different C-4 samples with the aid of principal component analysis, a multivariate statistical analysis approach often used to reduce the dimensionality of complex data. ToF-SIMS imaging was also used to obtain information about the spatial distribution of the various additives contained within the samples. The results indicated that the samples could potentially be characterized by their 2-D chemical and morphological structure, which varied from sample to sample. XPS analysis also showed significant variation between samples, with changes in the atomic concentrations, as well as changes in the shapes of the high-resolution C 1s and O 1s spectra. These results clearly demonstrate the feasibility of utilizing both ToF-SIMS and XPS as tools for the direct characterization and differentiation of C-4 samples for forensic applications.