Standard reference materials for the determination of polycyclic aromatic hydrocarbons

Summary Since 1980 a number of Standard Reference Materials (SRM's) 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 SRM's 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 SRM's 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 SRM's available from NBS for use in the determination of PAC are described and the concentrations of PAC determined in the natural matrix SRM's are summarized and compared. The primary analytical techniques used for the measurement of PAC in these SRM's were gas chromatography, liquid chromatography, and gas chromatography/mass spectrometry.

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Standardreferenzmaterialien für die Bestimmung von polycyclischen aromatischen Kohlenwasserstoffen

     

Assessment of ICP-MS for routine multielement analysis of soil samples in environmental trace element studies

Summary The suitability of inductively coupled plasma mass spectrometry (ICP-MS) following acid digestion of samples was evaluated for the routine determination of trace elements in contaminated and control soil samples. The contaminated samples were collected near an expressway and two secondary lead smelters in Toronto. All samples were acid digested in pressure vessels using a combination of reagents including hydrofluoric and perchloric acids. Consequently, the total amount of the elements (Pb, Sb, Cd, As, Mn, Mo and Cr) were being determined. In the case of lead direct comparison and isotope dilutional MS procedures were compared. Standard Reference Materials (SRM's) were run to allow an assessment of precision and accuracy. Isotope ratios were determined in the contaminated samples to evaluate whether this approach could be used, routinely, to determine the source of the lead. National Bureau of standards (NBS) 981 isotope ratio reference sample was used to evaluate the accuracy of the lead isotopic ratio data.Generally, the results obtained for the total amounts of the elements in the SRM's were in satisfactory agreement with the certified values. The measured isotopic ratios had a small positive bias compared to the NBS certified values. Isotope dilution MS values for Pb were superior in accuracy and precision to those obtained by direct comparison calibration. At the present state-of-the-art, routine isotope ratio measurements are not good enough for source typing in a study such as this. Values obtained in the present investigation compared well with those reported in a 1974 study of same areas.     

Determination of Ba, Fe, Sr, and Zr in silicate materials with ED-XRF using241Am excitation source

The possibilities of ED-XRF with²⁴¹Am excitation source are evaluated in the analysis of geological materials: rocks, clays, soils, and sediments. The calibration curves are made using different SRM's. Data from the analysis of various SRM's are presented.     

Use of standard reference materials as multielement irradiation standards in neutron activation analysis

Standard reference materials, normally used to check accuracy and precision of analytical methods or for interlaboratory comparisons, are proposed for use as multielement irradiation standards in neutron activation analysis (NAA). The advantages are simplicity of operation, and elimination of errors inherent in the preparation of a large number of synthetic standards at the trace element level. Examples of the approach are illustrated in the analysis of geological materials, soils, sediments, meteorites, lunar samples, coal and fly ash using the USGS diabase W-1 as the irradiation standard. Plant materials and animal tissue are analyzed using NBS Orchard Leaves as the irradiation standard. Best values for four popular SRM's (W-1, Bowen's Kale, Orchard Leaves, and Bovine Liver) are tabulated to facilitate further use of the proposed approach to multielement neutron activation analysis.     

Determination of some additional trace elements in certified standard reference materials (soils, sludges, sediment) by ICP-emission spectrometry

Summary The concentration of some additional elements like Ag, Au, B, Ba, Be, Co, Li, Mo, Na, P, Pt, and S in some standard reference materials (SRM's) were determined by using high resolution ICP (Inductively Coupled Plasma)-emission spectrometry. The materials used were three soils and three sludges from the BCR (Community Bureau of Reference, European Communities) and one sediment from NBS (National Bureau of Standards, USA). The aqua regia soluble and the total content using HF-treatment were shown. The given results are the mean values of 6 independent measurements for each material and for each decomposition method (certification conditions). The quantitative determination of Au and Pt was not possible due to severe spectroscopic interferences, which could not be eliminated. Beside the concentration values also the measured detection limits and the limits of determination for each element in the matrices under investigation are given. For comparison and for testing the validity of the decomposition procedures, also certified elements like Cd, Cu, Ni and Zn have been analysed in all the samples.

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Bestimmung einiger zusätzlicher Spurenelemente in zertifizierten Referenzmaterialien (Boden, Schlamm, Sediment) durch ICP-Emissions-Spektrometrie

     

Abtrennung und radiochemische Bestimmung geringer Mengen Seltener Erden in extraterrestrischem Material

The detection limits in neutron activation analysis are up to the standards of extraterrestrical matter analysis. Instrumental analysis is possible only after a group separation of the rare earth elements. The measurements requires a 26 day decay period. If results are desired within a shorter time interval the individual rare earth elements have to be separated. Gas chromatography and electrophoresis were applied in this work. Gas chromatography of metal chelates using radioactive reagents with high specific activity significantly improves the detection limits. The gas-chromatographic separations, however, should be only regarded as model experiments. The experimental results were obtained much faster (within 12 h) by applying high voltage electrophoresis of rare earth elements. Because of the excellent separation, the rare earth elements can be determined by automatic β-liquid scintillation spectrometry with high counting yields.     

Statistical aspects of the use of reference materials

Summary Interlaboratory testing, even when coupled with careful calibrations in terms of SRM's, is a complex process. It often raises problems that only the subject-matter specialists can solve. The problems are definitely not solved by rejecting test results or laboratories.     

The traceability of analytical measurements

 Traceability to the System International (SI) is an important prerequisite for international comparability and uniformity of chemical measurements to ensure mutual recognition of the results. In theory, all measurements can be traced back to the seven base units of the SI. Although the traceability system works well for most physical measurements, in many analytical and in some spectrophotometric measurements this system is not satisfactory. This paper describes the particular and practical problems and the contribution of the Romanian National Institute of Metrology in this field. The paper discusses the following concepts: clearly defined targets in the form of requirement specification, knowledge of trueness and/or measurement uncertainty, and traceability through an unbroken chain of calibration to primary standards. Traceability and uncertainty being two concepts inherently coupled, two examples of assessment of the uncertainty of measurement results are given for two spectrophotometric methods currently used in chemical laboratories. Received: 17 July 1996 Accepted: 2 September 1996     

Trace determination of iron,cobalt, nickel and copper in zirconium fluoride by substoichiometric radioactivation analysis

Trace amounts of transition elements (Fe, Co, Ni and Cu) in zirconium fluoride and NBS SRM's were determined by substoichiometric radioactivation analysis. The contents of impurities in sublimed sample were less than those of high-purity material and of reagent grade. The detection limits of these elements in zirconium fluoride were 10 ng/g for iron, 0.01 ng/g for cobalt, 1 ng/g for nickel and 0.1 ng/g for copper. The analytical results for iron, cobalt, nickel and copper in NBS SRM's were in good agreement with certified values.     

A test of comparative equilibration for determining non‐exchangeable stable hydrogen isotope values in complex organic materials

Comparative equilibration has been proposed as a methodological approach for determining the hydrogen isotopic composition (δD) of non‐exchangeable hydrogen in complex organic materials, from feathers to blood and soils. This method depends on using homogenized standards that have been previously calibrated for their δD values of non‐exchangeable H, that are compositionally similar to unknown samples, and that span an appropriate isotopic range. Currently no certified organic reference materials with exchangeable H exist, and so isotope laboratories have been required to develop provisional internal calibration standards, such as the keratin standards currently used in animal migration studies. Unfortunately, the isotope ratios of some samples fall outside the range of keratin standards currently used for comparative equilibration. Here we tested a set of five homogenized keratin powders as well as feathers from Painted Buntings and Dark‐eyed Juncos to determine the effects of extrapolating comparative equilibration normalization equations outside the isotopic range of keratin standards. We found that (1) comparative equilibration gave precise results within the range of the calibration standards; (2) linear extrapolation of normalization equations produced accurate δD results to ～40‰ outside the range of the keratins standards used (?187 to ?108); and (3) for both homogenized keratin powders and heterogeneous unknown samples there was no difference in variance between samples within and outside the range of keratin standards. This suggested that comparative equilibration is a robust and practical method for determining the δD of complex organic matrices, although caution is required for samples that fall far outside the calibration range. Copyright © 2009 John Wiley & Sons, Ltd.     

Standard reference materials (SRM's) for measuring genetic damage

Summary Standard reference materials were designed for the measurement of radiolytic products resulting from OH radical reaction with DNA in patients treated by radiation therapy. Deuterated thymine glycol and thymidine glycol are proposed as such SRM's; the synthesis of the former is described in detail. They might be of importance for optimising the therapy.     

Traceability of performance evaluation materials

One of the most critical elements of a performance evaluation (PE) program for radioactivity measurements is the traceability of the PE materials to the national standards. The requirements and criteria for the production of traceable environmental and radiobioassay PE materials have been defined by ANSI N42.22 and ANSI N13.30 standards. It is important to note that use of traceable source materials does not necessarily ensure the traceability of subsequently derived PE materials unless verification measurements exist in conjunction with the preparation processes. This paper describes the protocol currently used by NIST for the preparation and verification of air filter, acidified water, spiked soil, synthetic urine, and synthetic fecal PE materials for low-level radioactivity measurements. The process involves gravimetric dilutions and mixing of primary radionuclide NIST Standard Reference Materials (SRMs), addition of the derived master solution to sample matrices, and subsequent verification measurements. Several gamma-emitters were used to trace the gravimetric dilutions and spike addition through an unbroken chain of gamma comparison measurements. The massic activities of alpha- and beta-emitters in the diluted solutions and PE samples were also measured by radiochemical methods and compared with their gravimetric values. A correlation analysis demonstrated that the gamma emitters quantitatively followed ⁹⁰Sr, ²³⁸U, ²³⁸Pu, and ²⁴¹Am throughout the dilution and spiking and can be used as effective process monitors. The statistical results from t-tests, box plots, and normal probability tests suggested that traceability of radionuclides in the PE materials to their primary standards can be verified to within 1%, with an overall precision better than 2% (1s).     

Chemical Analyses of Canadian Reference Samples: SY-2 and SY-3

Abstract

Chemical analyses of the major and some of the minor constituents are reported for two new Canadian silicate rock standards recently introduced by the Department of Energy, Mines and Resources. To date quantitative chemical analyses have not yet been reported for these samples. The compositions of these rocks offer a useful range of values that are not currently covered by existing silicate rock standards.     

Thermal Analysis and Kinetic Study of Decomposition processes of Some Commercial Pesticides I. Triazine derivatives

The thermal behaviour of some commercial pesticides was studied by means of simultaneous TG-DSC measurements. Kinetic parameters relating to liquid—gas-phase transition processes were determined via a dynamic TG technique. Gas chromatography-mass spectrometry were used to make measurements on the gaseous products. The liquid—gas-phase transition processes of these compounds seem to be influenced by the substituent groups rather than by the side-chains. A chlorine substituent destabilizes some compounds, bringing closer together the temperatures of melting and liquid—gas-phase transition processes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gas chromatographic determination of volatile anaesthetic agents in blood. Part 1. Preparation of standard gas mixtures of volatile anaesthetic agents

A method for preparing standard gas mixtures of the volatile anaesthetics halothane, enflurane and isoflurane is described. Static mixtures of gases of known concentration can be prepared manometrically by measuring the required pressure of anaesthetic gas into a bulb and diluting to atmospheric pressure with air. Standard gas mixtures in the concentration range 0-4% V/V can be prepared with an accuracy of +/- 0.01% V/V, and the relative standard error of measurements of a single standard concentration is less than 0.8%. Significant adsorptive losses in the gas sampling valve were observed for gas standards prepared in the absence of any diluent gas. These losses were not detected for measurements of standards made up to atmospheric pressure in air. A comparison with calibration procedures currently in practice is presented.     

Chemical measurement and the law: metrology and quality issues

To facilitate just and sound decisions legal measurements must be reliable. The aim of this paper is to explore how this is currently achieved and how it might be better done. It considers the different types of legal proceedings, the role of chemical measurement, level of proof, the different types of chemical measurement, measurement units, the role of government, the chemical measurement industry and its control, legal metrology and the development of a measurement system based on metrological principles. It is argued that recent developments provide the basis for a robust support system, that but more needs to be done. It is also argued that the conventional approach to legal metrology has little place in chemical measurement, but that some controls are needed in some areas. In particular, a harmonised approach to international measurement standards is advocated. Received: 29 December 2000 Accepted: 8 January 2001     

A way of establishing quality of measurements in gas analysis—national and international aspects

Standardising quality of measurements at both the national and international level results in a unity in measurement that may be regarded a synonym of traceability. In gas analysis, the key issue in achieving this aim is production of gaseous reference materials. Establishing a network of secondary measurement standards at gaseous CRM producers’ sites in Ukraine might be interesting for those involved in gas analysis activities. Inevitably, problems concerning the recognition of measuring capabilities of both national metrological institutes and local CRM producers are now an international issue. Thus, the problems of national adoption of international standards, as well as harmonisation between different international documents are currently relevant, and Ukrainian experience may be useful to others in this field. Presented at the 3rd International Conference on Metrology, November 2006, Tel Aviv, Israel.     

Recent applications of gas chromatography with high‐resolution mass spectrometry

Gas chromatography coupled to high‐resolution mass spectrometry is a powerful analytical method that combines excellent separation power of gas chromatography with improved identification based on an accurate mass measurement. These features designate gas chromatography with high‐resolution mass spectrometry as the first choice for identification and structure elucidation of unknown volatile and semi‐volatile organic compounds. Gas chromatography with high‐resolution mass spectrometry quantitative analyses was previously focused on the determination of dioxins and related compounds using magnetic sector type analyzers, a standing requirement of many international standards. The introduction of a quadrupole high‐resolution time‐of‐flight mass analyzer broadened interest in this method and novel applications were developed, especially for multi‐target screening purposes. This review is focused on the development and the most interesting applications of gas chromatography coupled to high‐resolution mass spectrometry towards analysis of environmental matrices, biological fluids, and food safety since 2010. The main attention is paid to various approaches and applications of gas chromatography coupled to high‐resolution mass spectrometry for non‐target screening to identify contaminants and to characterize the chemical composition of environmental, food, and biological samples. The most interesting quantitative applications, where a significant contribution of gas chromatography with high‐resolution mass spectrometry over the currently used methods is expected, will be discussed as well.     

Structural studies of metal ligand complexes by ion mobility-mass spectrometry

Collision cross sections (CCS) have been measured for three salen ligands, and their complexes with copper and zinc using travelling-wave ion mobility-mass spectrometry (TWIMS) and drift tube ion mobility-mass spectrometry (DTIMS), allowing a comparative size evaluation of the ligands and complexes. CCS measurements using TWIMS were determined using peptide and TAAH calibration standards. TWIMS measurements gave significantly larger CCS than DTIMS in helium, by 9 % for TAAH standards and 3 % for peptide standards, indicating that the choice of calibration standards is important in ensuring the accuracy of TWIMS-derived CCS measurements. Repeatability data for TWIMS was obtained for inter- and intra-day studies with mean RSDs of 1.1 % and 0.7 %, respectively. The CCS data obtained from IM-MS measurements are compared to CCS values obtained via the projection approximation, the exact hard spheres method and the trajectory method from X-ray coordinates and modelled structures using density functional theory (DFT) based methods.     

Non-linear effects in the determination of paleotemperature U37(k') alkenone ratios by chemical ionization mass spectrometry

The performance of gas chromatography coupled to mass spectrometry in the positive chemical ionization mode using ammonia as reagent gas (GC-PCI-MS) in the analysis of C37 alkenones for paleotemperature estimation has been re-evaluated. In some conditions, the discrepancies observed in the measurement of the U37(k') index with this technique as compared with GC equipped with flame ionization detection (GC-FID) cannot be explained by differences in sensitivity between the tri- and diunsaturated alkenones. Thus, at low (currently <0.3) or high (currently >0.4) U37(k') values the GC-PCI-MS determinations may be observed to be lower or higher, respectively, than those measured with GC-FID. As shown by analysis of a series of synthetic C37 alkenone standards these discrepant results can be explained by non linear effects in the GC-PCI-MS response factors. Second-order polynomial functions provide equations that describe better the signal to amount of analyte ratios. Users of GC-PCI-MS should calibrate their instruments with standards of known C37 alkenone composition in order to minimize non-linear effects.