S. N. Chesler

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.

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.

Capillary supercritical fluid chromatography of explosives: Investigations on the interactions between the analytes, the mobile phase and the stationary phase

Abstract The independent effects of pressure and temperature in supercritical fluid chromatography on the capacity ratio on chromatographic resolution of some polar organic model compounds were investigated. Increasing the pressure isothermally leads to a steady decrease in retention and resolution. With changing temperature, a maximum in the capacity ratio as well as the resolution was observed. These observations may be related to a combination of gas chromatographic (GC) and liquid chromatographic (LC) theories of solute interactions with the mobile and stationary phases. However, pure GC- or LC-like behavior was not observed either below or above the critical point of the mobile phase. Capacity ratios for various explosives, propellants and related compounds were determined on capillary open tubular columns coated with either a non-polar methyl- or a polar cyanopropyl—phenyl-substituted siloxane stationary phase. The mobile phase for all studies was carbon dioxide. On the polar column, many of the solutes exhibited a good correlation between their bulk dipole moment and chromatographic retention. Deviations from this correlation could be explained by means of the physical or steric properties of these solutes. The elution order of the compounds on the non-polar column was similar to the order achieved using GC rather than LC.

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.

Analytical fluidic sampling systems

Abstract Fluidic logic sampling systems have been developed for analytical detectors such as the plasma chromatograph and flame ionization detector. Automated systems are reported for gases and vapor-phase samples which are rapid, quantitative and reproducible. Sample modulation systems, multiplexers, parallel-to-serial converters and sequential samplers have been developed which give no leakage or crosstalk signals. Other applications in analytical chemistry are proposed.

Liquid chromatography—gas chromatography procedure to determine the concentration of dibenzothiophene in a crude oil matrix

Abstract The concentration of dibenzothiopene in SRM 1582, Wilmington crude oil, was determined using a technique which combines liquid chromatography and gas chromatography. In particular, liquid chromatography was utilized for initial sample clean-up and separation of the thiophenes. A dual-flame photometric detector specific for sulfur-containing compounds was used as the detector for gas chromatography. In order to further minimize possible sources of error due to the natural hydrocarbon matrix of the oil, a standard addition method was also utilized.

Standard Reference Materials for the Determination of Polycyclic Aromatic Hydrocarbons in Environmental Samples -- Current Activities

SummaryRecent activities at the National Institute of Standards and Technology (NIST) related to the development of standard reference materials (SRMs) for the determination of polycyclic aromatic hydrocarbons (PAHs) are described. These activities include: (1) the development of four new calibration solution SRMs, a marine sediment SRM, and a frozen mussel tissue SRM; (2) noncertified measurements of PAHs for two additional sediment SRMs; and (3) the establishment of reference Ames bioassay mutagenicity values on three existing SRMs. Activities in progress include the recertification of the existing air particulate and diesel particulate SRMs and the preparation of a new diesel particulate extract SRM.

Analysis of nitrogen heterocycles in shale oil by a dual capillary column heart cutting technique

Abstract The analysis of nitrogen heterocycles in a shale oil matrix is described. A dual column gas chromatograph is used for the analysis after a simple sample preparation scheme is used. Details of the apparatus, especially the inter-column pneumatic microswitch, are given. Quantitation by the standard addition method using internal volume corrections is described. Future direction for further development of this technique is briefly discussed.

Supercritical fluid extraction-immunoassay for the rapid screening of cocaine in hair

Supercritical fluid extraction-radioimmunoassay (SFE-RIA) was evaluated as a rapid screening tool for the detection of cocaine residues in human hair. SFE was performed using carbon dioxide modified with triethylamine (TEA) and water, with off-line collection of extracted cocaine in methanol. Extracts were analyzed for the presence of cocaine using a commercially available solid-phase RIA kit. In order to develop a suitable RIA calibration method for reliable measurement of cocaine in SF extracts, calibration data was compared for methanolic standards both with and without the presence of the SF modifier. Methanol had only a minor impact on immunoassay performance, producing an 11% decrease in maximum binding counts. In contrast, the presence of TEA/H2O profoundly degraded assay performance, producing a 60% suppression in assay counts. To preserve RIA sensitivity, SF extracts were evaporated under nitrogen to remove the modifier and reconstituted in methanol for RIA analysis. Incorporation of the evaporation step permitted the use of modifier-free cocaine calibrators in methanol. Calibration data was at to a four-parameter logistic model. SFE-RIA analysis of a series of drug-free hair samples established an RIA cut-off value for distinguishing between a negative and presumptive positive cocaine sample at an SF extract concentration of 1.2 ng/mL, or a hair concentration of 0.07 ng/mg. The robustness of the SFE-RIA method was demonstrated by the analysis of a variety of hair samples from both drug users and non-users. The quantitative SFE-RIA findings correlated well with the values obtained by an acid incubation/GC-MS method.

Organic Marker Compounds for Environmental Analysis

Abstract Marker compounds have been used extensively in fields such as clinical chemistry, but their use in environmental analyses has been minimal. Two definitions of marker compounds and their use in environmental assessment will be discussed in this paper. The first definition is the use of marker compounds as internal reference compounds for quantitative analysis of pollutants. The second definition is their use as qualitative indicators of certain types of chemical pollution.