Development and Analysis of Three Diesel Particulate-Related Standard Reference Materials for the Determination of Chemical,Physical, and Biological Characteristics

The National Institute of Standards and Technology (NIST) has recently issued three Standard Reference Materials (SRMs) related to diesel particulate matter: SRM 1650a, Diesel Particulate Matter; SRM 2975, Diesel Particulate Matter (Industrial Forklift); and SRM 1975, Diesel Particulate Extract. These three materials have certified and reference concentrations for selected polycyclic aromatic hydrocarbons (PAHs) including many alkyl-substituted compounds. SRM 1650a is the reissue of an existing material and SRMs 2975 and 1975 represent new materials. The characterization of the PAH content of these three diesel particulate-related SRMs is presented with a discussion of the approach for the certification of PAH concentrations. In addition, the physical and biological characterization of these materials is discussed. A review of customer reported uses of these SRMs in the chemical, physical, and biological sciences is also provided.     

Liquid Chromatographic Determination of Polycyclic Aromatic Hydrocarbon Isomers of Molecular Weight 278 and 302 in Environmental Standard Reference Materials

Abstract

Polycyclic aromatic hydrocarbons (PAHs) of molecular weight (MW) 278 (dibenzanthracene isomers) and 302 (dibenzopyrene/dibenzofluoranthene isomers) are seldom measured in environmental samples. A multidimensional liquid chromatography (LC) procedure was developed for the quantification of isomers of MW278 and 302. The multidimensional LC procedure consists of normal-phase LC to isolate the PAH isomer groups followed by analysis of the isomeric groups by reversed-phase LC with fluorescence detection. Using the multidimensional LC procedure, six isomers of MW 278 and nine isomers of MW 302 were quantified in four environmental Standard Reference Materials (SRMs): coal tar (SRM 1597), air particulate matter (SRMs 1648 and 1649), and marine sediment (SRM 1941).     

Standard Reference Materials (SRMs) for the Determination of Polycyclic Aromatic Compounds--Twenty Years of Progress

In 1981 the National Bureau of Standards, now the National Institute of Standards and Technology (NIST), issued the first natural matrix Standard Reference Material (SRM) for the determination of polycyclic aromatic compounds (PACs), SRM 1580 Organics in Shale Oil. In the next 10 years, additional natural matrix SRMs were developed including air and diesel particulate matter, petroleum crude oil, coal tar, sediment, and mussel tissue. The SRMs represented the "first generation" of natural matrix SRMs for the determination of PACs. The SRMs had "certified" values for only 5 to 12 PACs; however, their development established the foundation for the implementation of the "two or more independent analytical techniques" approach for certification of individual PACs in environmental matrices. The requirement for use of different analytical techniques spurred the development of both gas chromatography (GC) and liquid chromatography (LC) approaches for the determination of PACs. Since the mid-1990s, the "second generation" of natural matrix SRMs has been issued by NIST with certified values for over 20 PACs in each material. The greater number of certified values in these SRMs was the result of the combination of measurements using reversed-phase LC with fluorescence detection, multidimensional LC, and GC with mass spectrometric detection using two or more stationary phases with different selectivity for polycyclic aromatic hydrocarbon (PAH) separations. This article discusses the significant developments in analytical methods and chromatographic separation of PAHs during the past 20 years that have resulted in the certification of over 25 SRMs, which are now used worldwide for the validation of analytical methods for the measurement of PACs in environmental matrices.     

Recertification of Standard Reference Material (SRM) 1649, Urban Dust,for the Determination of Polycyclic Aromatic Hydrocarbons (PAHs)

The National Institute of Standards and Technology (NIST) recently issued SRM 1649a, Urban Dust, with certified and reference values for 44 polycyclic aromatic hydrocarbons (PAHs). This material is a recertification of SRM 1649 which was issued in 1982 with certified values for only five PAHs. The PAHs were determined using the following analytical techniques: (1) reversed-phase liquid chromatography with fluorescence detection (LC-FL) for analysis of the total PAH fraction, (2) reversed-phase LC-FL for analysis of isomeric PAH fractions isolated by normal-phase LC (i.e., multidimensional LC), and (3) gas chromatography/mass spectrometry (GC/MS) for analysis of the PAH fraction using three different stationary phases, each with different selectivity for PAH separations. The results from the different techniques are compared and discussed. SRM 1649a is currently the most extensively characterized environmental matrix SRM with respect to PAH constituents.     

Particle Associated Polycyclic Aromatic Hydrocarbons (PAHS) in Urban Air of Agra

Total Suspended Particulate Matter (TSPM) samples were collected at Nunhai Agra from April to September 2006. The concentrations of 16 PAHs in aerosols were quantified. The dominated predominant PAHs in TSPM include high molecular weight (HMW) congeners BghiP, DbA, IP and BaP. Nap and Acy were not detected in any of the samples. The sum of 14 priority PAHs ranged from 150 to 480 ng m^?3 with a mean value of 269 ± 121 ng m^?3. The Results indicated that PAH concentrations at Nunhai were higher than in other industrial sites, but are comparable to those measured in several urban Chinese cities, however, and less than the industrial locations of China. Higher HMW PAH concentration were attributable to higher rates of emissions as well as or greater scavenging and adsorption of vapor phase PAH on available TSPM. Potential sources of PAHs in aerosols were identified using the diagnostic ratios between PAHs. Vehicular emissions were the main contributors of particulate-associated PAHs, with minor contribution from stationary combustion sources may also contribute to the particulate PAHs. PAHs in aerosols were predominantly from gasoline and diesel engines.     

Determination of Semivolatile and Particulate Polycyclic Aromatic Hydrocarbons in SRM 1649a and PM 2.5 Samples by HPLC-Fluorescence

The concentrations of 15 "priority pollutant" semivolatile and particulate polycyclic aromatic hydrocarbons (PAHs) were determined in three sets of samples supplied by the National Institute for Standards and Technology (NIST) as part of an interlaboratory analytical exercise. The purpose of the exercise, organized by NIST and the U.S. Environmental Protection Agency, was to determine the comparability of measurements for various organic analytes among the participating laboratories, and to establish consensus values for SRM 1649a and interim materials. The commercially available SRM 1649a Atmospheric Urban Dust and two subsamples of this popular reference material were analyzed: an extract designated as Air Particulate Extract, and a resieved portion labeled Air Particulate I. The method used in our laboratory for the exercise consists of the extraction of the PAHs from the solid samples by ultrasonication, followed by separation and quantification using high-performance liquid chromatographyfluorescence detection. The accuracy and precision of the results obtained by our analytical protocol and by 14 other participating laboratories were evaluated using the International Union of Pure and Applied Chemistry guidelines of z-scores ( = 25% of the exercise assigned value) and p -scores. Using these guidelines the accuracy of our method provided results that are satisfactory for all 15 target PAHs (|z| h 2) determined in the Air Particulate Extract and, except for fluorene, in the Air Particulate I sample. Finally, application of the methodology is demonstrated for the quantification of PAHs present at the pg m m 3 range in PM 2.5 samples collected from 163 m 3 of air in the Los Angeles basin.     

乌鲁木齐市大气可吸入颗粒物中多环芳烃与颗粒物比表面积、气象因素相关性的探讨

通过对2011年1月至12月期间乌鲁木齐大气可吸入颗粒物(PM2.5、PM2.5-10)中多环芳烃(PAHs)浓度、颗粒物比表面积的分析,并查询采样期间的气象因素(风速、湿度和温度)。分别将多环芳烃浓度和气象因素、颗粒物表面积做相关性分析。其中可吸入颗粒物PM2.5中除蒽之外,PM2.5质量浓度、各多环芳烃的浓度随其PM2.5比表面积均为正相关;PM2.5-10中,PM2.5质量浓度、各多环芳烃的浓度随其PM2.5-10比表面积也均为正相关。PM2.5和PM2.5-10质量浓度和气象参数之间的相关关系具有很明显的季节性特征。在采暖和非采暖期间,PM2.5和PM2.5-10中的总多环芳烃和温度之间为负相关性;采暖期间,可吸入颗粒物中所含的总PAHS浓度和风速也呈负显著相关,在非采暖期间PM2.5-10的质量浓度和风速呈正相关,而多环芳烃与风速之间都没有显著相关性。采暖期间,颗粒物的浓度及对应的∑PAHS浓度和大气湿度呈显著正相关,而在非采暖期间总多环芳烃浓度和湿度之间没有显著的相关性。     

Standard reference materials for cements

The eight portland cements and two calcium aluminate cements in the Standard Reference Material (SRM) 1880 series are among the most popular SRMs in the catalog of the National Institute of Standards and Technology (NIST) Standard Reference Materials Program. Numerous laboratories rely on them for elemental analysis and qualification for ASTM C 114-00 Standard Test Methods for Chemical Analysis of Hydraulic Cement. NIST has collected new candidate materials from around the world and partnered with Construction Technology Laboratories (CTL) in their preparation and certification. This paper describes the procedures taken at NIST and CTL to prepare and test materials for certification including the homogeneity testing, the X-ray fluorescence methods and the statistical data analysis performed for value assignment.     

Polycyclic aromatic hydrocarbon emissions of non-road diesel engine treated with non-thermal plasma technology

Non-road diesel engines are important polycyclic aromatic hydrocarbon (PAH) sources in the environment due to their high emission concentration compared to on-road diesel engines. Particle- and gas-phase PAH concentrations of a non-road diesel engine were investigated. Non-thermal plasma (NTP) as an effective after-treatment technology was used to reduce PAH emissions. The results showed that particle-phase PAH concentrations were 329.7 µg/m³, 3,206.7 µg/m³, and 1,185.7 µg/m³ without the action of NTP at three different engine loads respectively. Relatively low concentrations were measured for gas-phase PAHs. Excellent linearity was shown for particle-phase with total PAH concentrations both with, and without, NTP. The gas-phase PAH concentrations linearly increased with engine load without NTP. The five most abundant compounds of PAHs were among low molecular weight (LMW) and medium molecular weight (MMW) compounds. Total PAH cleaning efficiency was beyond 50% when treated with NTP at the three different engine loads. We hypothesized that naphthalene (Nap) concentrations increased greatly at 60% and 80% engine loads because it was produced within the plasma zone by decomposition of high molecular weight (HMW) PAHs. The PAHs content of particulate matter (PM) aggregation at 60% load was approximately three times higher than at 40% and 80% loads. High correlation values were observed for MMW PAHs with total PAH concentrations. Correlations of PAH concentration reduction could be important to clarify the PAH reduction mechanism with NTP technology.     

Determination of PAHs in Combustion-Related Samples and in SRM 1597, Complex Mixture of PAHs from Coal Tar

Three types of combustion sample extracts, smokeless coal, smoky coal, and wood, were analyzed for a range of polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic sulfur heterocycles (PASH). Standard Reference Material (SRM) 1597, Complex Mixture of PAHs from Coal Tar, was also analyzed as a control sample and for the determination of a larger number of PAHs relative to those determined previously. Target analytes included many alkyl-substituted PAHs such as dimethylphenanthrenes, methylfluoranthenes, and methylpyrenes. The analytical methods included sample clean-up and the selection of specific stationary phases to accomplish unique separations of PAHs. Clean-up involved the use of normal-phase liquid chromatographic isolation of PAHs based on the number of aromatic carbons and a total PAH fraction, PAHs in the resulting fractions were separated by gas chromatography using two stationary phases with different selectivities and analyzed using mass spectrometry. These methods are discussed below and results are presented with an emphasis on the relative concentrations and distribution of PAHs in the combustion samples.     

Stability of Polycyclic Aromatic Hydrocarbons in Frozen Mussel Tissue

The stability of polycyclic aromatic hydrocarbons (PAHs) in frozen mussel tissue (stored at -80 °C and -120 °C was assessed by analyzing samples of SRM 1974 and SRM 1974a, Organics in Mussel Tissue (Mytilus edulis), since the initial certification analyses. Results of analyses of SRM 1974 and SRM 1974a after 10 years and 6 years of storage, respectively, indicate that the PAH concentrations have not changed. Comparison of results from the analyses of frozen versus freeze-dried mussel tissue samples indicate significant losses of the more volatile PAH such as naphthalene and methylnaphthalenes during the freeze-drying process.     

An easy correlation to determine soluble and insoluble fractions in diesel particulate matter

Mathematical fitting of experimental emission data from five different fuels and three mixtures of biodiesel and reference diesel operating under diverse conditions allows to propose an easy equation to calculate both the insoluble and soluble fractions in Diesel Particulate Matter.

The relative importance of each mechanism involved in the DPM formation process is also mathematically quantified. Two different mechanisms are principally found to take place during DPM formation. In a first stage (scrubbing effect), adsorbed sulphuric acid reacts with organic compounds in the exhaust to form heavy hydrocarbons which are likely to remain in the condensed phase. The remaining hydrocarbons undergo an absorption process and are retained on particles in the liquid phase. However, some light hydrocarbons may escape from the filter system and are not quantified as soluble organic fraction (SOF). The presence of two retention mechanisms makes it necessary to develop an accurate extraction technique to quantify the soluble organic fraction.     

Calibration in 1976 and 1983 of didymium glass filters issued as NBS standard reference materials

In 1983, a new supply of didymium glass filters was prepared since the stock calibrated in 1976 has been very useful for wavelength calibration and the inventory has been depleted. Results for representative samples of the new filters are presented. The new supply of glass has been calibrated by the batch mode and will be designated Standard Reference Materials (SRM) 2009A and 2010A. During the latter part of 1976, research was begun to characterize didymium glass filters for use with visible spectrophotometers with bandwidth in the range 1.5 to 10.5 nm. These filters were found to produce a smaller wavelength uncertainty than previously issued filters. Also, it was found that points of inflection in the transmittance curve could be used to supplement the data for transmittance minima. The results of that research were SRM 2009, 2010, 2013, and 2014. The same techniques were applied in 1983. Also, the results from 1983 and 1976 for one of the Master filters are compared.     

POLYCYCLIC AROMATIC HYDROCARBONS OF DIESEL AND GASOLINE EXHAUST AND DNA ADDUCT DETECTION IN CALF THYMUS DNA AND LYMPHOCYTE DNA OF WORKERS EXPOSED TO DIESEL EXHAUST

Particles present in urban air pollution are mainly derived from diesel- and gasoline-fueled vehicles. Exhaust emission is able to cause several health effects in humans including mutagenicity and carcinogenicity. Polycyclic aromatic hydrocarbons (PAHs) were measured in diesel and gasoline particulate extracts and DNA binding to CT DNA (±S9 and ±XO) was investigated. A large difference in content of 14 PAHs in diesel and gasoline extracts was observed, showing higher concentration of 14 PAHs, 6 carcinogenic PAHs, benzo[a]pyrene (B[a]P) in diesel than in gasoline extracts. Selected PAH standards of B[a]P, benzo[c]fluoranthene (B[c]F), and 3-nitrobenzanthrone (NBA) were used in ³²P-postlabeling/polyacrylamide gel electrophoresis (PAGE) technique to identify CT DNA adducts formed by diesel particulate extracts. CT DNA adduct formation was higher for diesel extracts in comparison with gasoline extracts; however, no clear origin of DNA adducts derived from B[c]F-, 3-NBA-, B[a]P was detected. ³²P-postlabeling/PAGE was a useful assay for analyzing and identifying PAH-DNA adducts. Occupational exposure to particulate and volatile PAH concentrations were evaluated using personal air samples and lymphocyte DNA adducts as markers of exposure. Overall air PAH concentrations were low in all eight workplaces, consisting of 97% of vapor phase compounds. DNA adducts analyzed by ³²P-postlabeling assay were compared between the butanol and nuclease P1 enrichment procedures. Only in winter samples of exposed workers, butanol extraction revealed significantly higher adduct levels in comparison with those of control persons. No differences in adduct levels between exposed and control persons in summer were detected by using either butanol extraction or nuclease P1 treatment. Total concentrations of particulate and volatile PAHs measured in eight workplaces in winter showed a significant correlation with total DNA adducts analyzed in workers' lymphocytes (r = 0.852N = 8, p = .007).     

Standard Reference Materials to support measurement of fatty acids

The National Institute of Standards and Technology offers a variety of natural‐matrix and solution‐based Standard Reference Materials (SRM) that are characterized for fatty acid composition. The natural‐matrix SRM are intended primarily for use as control materials, but other uses include method validation, the development of new analytical methods, and use as a component in achieving traceability of measurements. The use of complex‐matrix reference materials for instrument calibration is not recommended; solution calibrants are better suited to this task. In addition to calibration, solution SRM can be used as spiking solutions for fortification of samples, in studying extraction recoveries, for developing chromatographic separations, and as authentic standards for identifying constituents in more complex‐matrix extracts. The use of SRM to support the measurement of fatty acids is relevant to a broad spectrum of applications including compliance with and accuracy of nutritional labeling, food manufacturing tolerances (e. g., infant formulas), traceability of measurements for food exports, clinical nutritional measurements, and characterization of alternative energy sources (e. g., biodiesel). Currently, nearly 30 SRM are available with certified, reference, and information values reported for fatty acids. Additional SRM are under development that will complement these reference materials by providing fatty acid profiles in different types of matrices.     

POLYCYCLIC AROMATIC HYDROCARBONS IN BALTIC SEA SEDIMENTS

Present concentrations of parent polycyclic aromatic hydrocarbons (PAHs) were studied in bottom sediments of the Baltic Sea. Sediments were collected in 2001 and 2002 from the Gulf of Finland, the Northern Baltic Proper, the Eastern Gotland Basin, the Southern Baltic Proper, and Kattegat. Parent PAHs were quantified by liquid chromatography with fluorescence detection. The sum of 13 PAHs in 1 cm slices in the first 5 cm varied between 64 and 5161 ng/g (dw) depending on the bottom type. The most contaminated area was in the Eastern Gotland Basin, and the most abundant PAH components found in sediments were fluoranthene, benzo[b]fluoranthene, benzo[ghi]perylene, and indeno[1,2,3-cd]pyrene. The studied PAHs were both pyrolytic and petrogenic in origin. In addition, the concentrations of indeno[1,2,3-cd]pyrene and benzo[ghi]perylene indicated a contribution from diesel engines, which may indicate pollution caused by the steadily increased shipping in the Baltic Sea.     

Comparison of Liquid Chromatography with Fluorescence Detection and Gas Chromatography/Mass Spectrometry for the Determination of Polycyclic Aromatic Hydrocarbons in Environmental Samples

Liquid chromatography (LC) with fluorescence detection and gas chromatography/mass spectrometry (GC/MS) have been compared for the determination of polycyclic aromatic hydrocarbons (PAHs) in a variety of environmental samples. Three sets of data are presented in this paper in which LC/fluorescence and GC/MS were used for the analysis of the same samples. These three data sets include the comparison of results from: (1) certification measurements for three natural matrix Standard Reference Materials (SRM's), (2) an international round robin for the determination of PAHs in air and diesel particulate samples, and (3) the analysis of four marine sediment reference materials. The results from these studies indicate that the two techniques generally provide comparable results for the measurement of PAHs in environmental samples (in the range of 0.1 to 300 ng/g), with differences in the two techniques between 5–20%. However, at low levels, anthracene and perylene are best measured using LC/fluorescence because of their selective and sensitive fluorescence detection characteristics. In contrast, GC/MS provides more accurate results for the determination of benzo[ghi]perylene because of its low fluorescence sensitivity.     

Antiestrogenic Activity of Extracts of Diesel Exhaust Particulate Matter in MCF-7 Human Breast Carcinoma Cells

Diesel exhaust particulate matter (DEP) was collected from three commercial diesel engine vehicles and DEP extracts (DEPEs) were prepared from each. The estrogenic and antiestrogenic activities of the DEPE samples were examined using an estrogen response element (ERE)-driven luciferase reporter gene assay in MCF-7 human breast cancer cells. While DEPE samples did not exhibit significant estrogen agonist activity alone, they suppressed 17 g -estradiol (E 2 )-induced luciferase activity without decreasing cell viability. Several polycyclic aromatic hydrocarbons (PAHs) acting as aryl hydrocarbon receptor (AhR) agonists were detected in the DEPEs and their concentrations were higher in DEPE samples with higher antiestrogenic activity. DEPE samples elevated cytochrome P450 (CYP) 1A1 activity. f -Naphthoflavone, an AhR antagonist, and SKF-525A, a nonselective CYP inhibitor, reversed and enhanced the antiestrogenic activity of DEPE samples, respectively. These results demonstrate that DEPE has antiestrogenic activity and this effect is primarily due to the PAH constituents acting as AhR agonists.     

DNA Adducts Derived from Diesel Emissions - Assessment of Genotoxic Potency in Vitro and Human Exposure Monitoring

Diesel particle extracts, which originated from three different diesel fuels, were used to study the activation of polycyclic aromatic hydrocarbons (PAHs). DNA adducts were analyzed in vitro calf thymus, human skin tissue culture and in lymphocytes isolated from diesel exposed workers. Direct-acting mutagens (e.g. nitro-PAHs) measured by Ames test were compared with DNA adducts formed in vitro by nitroreductive xanthine oxide enzyme. PAH-DNA adducts were analyzed by ³²P-postlabeling, and when characterizing adducts from skin DNA, a solid-phase micro extraction (SPME) method was developed for sample preparation before HPLC analysis. A good accordance between mutagenicity and DNA adducts showed that the three extracts contain higher amounts of direct-acting PAHs than the PAHs needing S9 activation. Skin DNA adducts demonstrated two-fold differences between the tissue cultures. ³²P-postlabeling and HPLC analysis did not confirm the identity of skin DNA adducts with the BPDE-DNA standard. The pilot study on 13 diesd exposed bus garage and waste collection workers showed low levels of PAH exposure (<50 ng/m³) and lymphocyte PAH-DNA adducts less than 2 adducts/10⁸ nucleotides.