Willie E. May

Determination of polycyclic aromatic hydrocarbons by liquid chromatography

Abstract Reversed-phase liquid chromatography (LC) using fluorescence detection is a powerful analytical technique for the measurement of polycyclic aromatic hydrocarbons (PAHs) in environmental samples. The National Institute of Standards and Technology (NIST) has been involved in the development of LC methods for the measurement of PAHs since the mid- 1970s particularly for the development of standard reference materials (SRMs) for PAH measurements in environmental samples. The NIST experience in the use of LC for the determination of PAHs in environmental samples is summarized in this paper including: selection of the appropriate column, approaches to analyzing complex PAH mixtures, and the accurate quantitation of PAHs in environmental samples.

Standard reference materials for the determination of polycyclic aromatic hydrocarbons

SummarySince 1980 a number of Standard Reference Materials (SRMs) have been issued by the National Bureau of Standards (NBS) to assist in validating measurements for the determination of polycyclic aromatic hydrocarbons (PAH) and other polycyclic aromatic compounds (PAC). These SRMs are certified for selected PAC and range in analytical difficulty from calibration solutions to complex natural matrix materials, such as air and diesel particulate matter, shale oil, and crude oil. In the past year three new SRMs have been introduced: (1) SRM 1647a “Priority Pollutant PAH in Acetonitrile”, (2) SRM 1491 “Aromatic Hydrocarbons in Hexane/Toluene”, and SRM 1597 “Complex Mixture of PAH from Coal Tar”. The SRMs available from NBS for use in the determination of PAC are described and the concentrations of PAC determined in the natural matrix SRMs are summarized and compared. The primary analytical techniques used for the measurement of PAC in these SRMs were gas chromatography, liquid chromatography, and gas chromatography/mass spectrometry.

Standard reference materials for chemical and biological studies of complex environmental samples

Standard Reference Materials (SRMs) from the National Institute of Standards and Technology (NIST) are often used in methods development and interlaboratory comparison studies since they are homogeneous and readily available to the scientific community. SRM 1649 (urban dust/organics), SRM 1650 (diesel particulate matter), and SRM 1597 (complex mixture of polycyclic aromatic hydrocarbons from coal tar) are three environmental samples which have been used by the scientific community for these purposes. These SRMs were originally developed to assist laboratories in validating analytical procedures for the determination of polycyclic organic compounds in complex mixtures. In addition, these SRMs have been valuable for the comparison of methodologies for bacterial bioassays and the development of bioassay-directed fractionation and bioassay-directed chemical analysis techniques. Most recently these SRMs were chosen for use as test samples in a collaborative study coordinated by the World Health Organization--International Programme on Chemical Safety. This paper provides a summary of much of the work to date (published and unpublished) on the chemical and biological characterization of these three SRMs. Information regarding the availability of other NIST SRMs that might be useful for these types of studies are provided also.

Quantification of polycyclic aromatic hydrocarbons and nitro-substituted polycyclic aromatic hydrocarbons and mutagenicity testing for the characterization of ambient air particulate matter☆

Abstract As part of a study to identify mutagenic and potentially carcinogenic compounds in urban air particulate extracts, the polycyclic aromatic hydrocarbon (PAH) mixture isolated from a large sample collected in Philadelphia, PA, was characterized by liquid chromatography (LC), gas chromatography (GC), and gas chromatography-mass spectrometry (GC-MS). After isolation of the aromatic fraction from the extract using classical liquid-liquid partitioning and silica gel column chromatography, the PAH fraction was isolated by normal-phase LC. A number of the major PAH constituents were quantified by GC and LC. Quantification of the minor constituents was accomplished by further subfractionation of the PAH mixture into eight fractions based on the number of aromatic carbons in the PAH. These fractions were then characterized by GC and GC-MS. More than 100 PAH components were quantified in this sample. Approximately 40 unsubstituted PAH and 10 methyl-substituted PAH were identified based on GC retention, LC retention, fluorescence, and/or mass spectral data. Several nitro-substituted PAH were also found in the PAH fraction and the more polar fractions isolated from the original aromatic fraction.

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

Abstract 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 (SRMs), (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...

Design and Implementation of a Collaborative Study of the Mutagenicity of Complex Mixtures in Salmonella Typhimurium

In 1987, the International Programme on Chemical Safety (IPCS) in collaboration with the U.S. Environmental Protection Agency (U.S. EPA) and the U.S. National Institute of Standards and Technology (U.S. NIST) initiated an international collaborative study of the mutagenicity of complex environmental mixtures in the Ames Salmonella typhimurium mutation assay. The objectives of this study were: (1) to estimate the inter- and intra-laboratory variability associated with the extraction of mixtures for bioassay, (2) to estimate the inter- and intra-laboratory variability associated with the Salmonella typhimurium bioassay when applied to complex mixtures, and (3) to determine whether standard reference complex mixtures would be useful in mutagenicity studies and to evaluate whether reference or certified mutagenicity values determined from this collaborative study should be reported. The complex mixtures used in this study were selected from standard reference materials (SRMs) which had previously been issued by the U.S. NIST as SRM 1597 (coal tar), SRM 1649 (diesel particulate matter) and SRM 1650 (urban air particulate matter) with certified values for polycyclic aromatic hydrocarbons. These SRM complex mixtures are available to scientists as reference standards for analytical chemistry research and are under consideration as SRMs for mutagenicity studies of complex environmental mixtures. This paper briefly describes the final study design, protocol, selection of the complex mixtures, and implementation of this international study.

The Application of Perdeuterated Polycyclic Aromatic Hydrocarbons (PAH) as Internal Standards for the Liquid Chromatographic Determination of PAH in a Petroleum Crude Oil and Other Complex Mixtures

Abstract A sequential liquid chromatographic (LC) procedure for the determination of polycyclic aromatic hydrocarbons (PAH) in a petroleum crude oil and other complex mixtures is described. The procedure includes normal-phase LC on an aminosilane column to isolate fractions containing isomeric PAH and reversed-phase LC on a polymeric C18 column to separate the individual PAH isomers. Appropriate perdeuterated PAH are added to the sample so that each isomeric fraction will contain one internal standard. The perdeuterated PAH are excellent internal standards for this sequential LC procedure. Perdeuterated PAH have normal-phase and reversed-phase LC retention characteristics similar to those of the parent PAH. In the normal-phase LC separation, the perdeuterated PAH elute in the same fraction as the parent PAH. In the reversed-phase LC separation, the perdeuterated PAH elute first and are generally resolved from the parent PAH. The optimized spectrofluorometric detection of each PAH analyte is accomplished b...

Modification of Selectivity in Reversed-Phase Liquid Chromatography of Polycyclic Aromatic Hydrocarbons Using Mixed Stationary Phases

Abstract Monomeric and polymeric C18 materials provide significantly different selectivities for polycyclic aromatic hydrocarbons (PAH) in reversed-phase liquid chromatography. Selectivity factors vary in a regular manner with respect to surface concentration of C18 groups on different C18 columns. In this study, we investigated the feasibility of “customizing” a C18 column to provide an intermediate selectivity by mixing 5-μm polymeric C18 material from two different lots with high and low C18 surface concentrations. Polymeric C18 materials from different production lots were mixed in ratios of 30/70, 50/50, and 70/30 (w/w). Selectivity factors for these columns were found to be similar to those predicted by the linear addition of the selectivities of the two individual phases. The PAH selectivities on these mixed columns were also found to be comparable to data obtained from coupled short columns of appropriate lengths each containing one of these different C18 materials. These studies indicate that col...

Analytical Standards and Methods for the Determination of Polynuclear Aromatic Hydrocarbons in Environmental Samplest

Abstract Standard reference materials (SRMs) have been produced, certified, and issued by the United States National Bureau of Standards (NBS) since 1905. NBS currently issues more than 1000 SRMs of various types, including nuclear materials, rubber, clinical and environmental trace metal standards. The most recent addition to this group is a series of environmental trace organic materials with certified concentrations of selected polynuclear aromatic hydrocarbons (PAH), phenols, and N-heterocyclic compounds. Until recently, trace organic SRMs were non-existent due to the lack of analytical methodology necessary for certification. Details concerning the analytical methods developed and used for certification of the concentrations of several PAH in SRMs 1580 (Organics in Shale Oil), 1644 (Generator Columns for PAH in water), 1647 (PAH in Acetonitrile), and 1649 (Urban Particulate Matter) are given along with some suggested uses for these SRMs.

Detectors for Liquid Chromatographic Analysis for Polynuclear Aromatic Hydrocarbons

Abstract A number of liquid chromatographic detectors of various types have been evaluated for both selectivity and sensitivity for the detection of polynuclear aromatic hydrocarbons (PAH). Detection limits for fixed and variable wavelength UV photometers, filter fluorimeters, and spectrofluorimeters have been determined. The utility of each of these types of detectors for use in the reversed-phase HPLC analysis of environmental extracts containing trace levels of PAHs is discussed.