Determination of rare earth elements in geological samples by inductively-coupled plasma atomic emission spectrometry after oxalate coprecipitation and cation-exchange column separation

A method for separation and determination of traces of 14 rare earth elements (REEs) in geological samples is described. Determination by inductively-coupled plasma atomic emission spectrometry follows oxalate coprecipitation of the REEs with calcium as carrier and cation- exchange column separation in nitric acid. The combination of the two separation techniques improved the low recoveries found for Sm, Eu, and Gd when only ion-exchange was used, especially for iron- and aluminum-rich samples. The method was applied to the analysis of geological standard materials NBS SRM 688 (basalt), NBS SRM 278 (obsidian), GSJ JB-1 (basalt), GSJ JA- 2 (andesite), and CCRMP SY-3 (syenite). The results were evaluated on the basis of chondrite- normalized rare earth element distribution patterns.     

Purge and trap flame photometric gas chromatography technique for the speciation of trace organotin and organosulfur compounds in a human urine standard reference material (SRM)

Ultratrace levels of organotin species and an organosulfur compound were detected in a National Bureau of Standards (NBS) human urine Standard Reference Material, SRM 2670, and a previously certified urine SRM 2672, using a purge and trap system coupled to a gas chromatograph equipped with a flame photometric detector. samples of the SRM were treated with sodium borohydride to form volatile tin hydrides. Species detected included dimethyltin (1.04 ng/ml), butyltin (0.03 ng/ml), and dimethyl-disulfide (2.73 ng/ml) in the new stock of freeze dried human urine SRM 2670 being prepared for issue by NBS and methyltin (1.0 ng/ml), butyltin (1.5 ng/ml), and inorganic tin (28.1 ng/ml) in the old stock of SRM 2672. This analytical technique should have useful applications in studies that are needed to develop a toxicological data base and monitoring programs for human organotin exposure.     

Distribution patterns of rare-earth elements in biological materials evaluated by radiochemical neutron activation analysis

This study deals with the quantitative determination of eight REE's viz, La, Ce, Nd, Sm, Eu, Tb, Yb, and Lu as an Integral part of a post-irradiation chemical separation scheme for the determination of 14 trace elements in biological materials. REE values are given for NBS Orchard Leaves SRM 1571, NBS Bovine Liver SRM 1577 and Bowen's Kale, as well as for some other biological (reference) materials of plant, animal and human origin. Chondritic-normalized REE patterns of these materials are discussed. It is shown that differentiations in REE-pattern between soil and plant may occur, and also that within the human body different modes of fractionation of REE's take place.     

Trace rare earth element analysis of IAEA Hair (HH-1), Animal Bone (H-5) and other biological standards by radiochemical neutron activation

A radiochemical neutron activation analysis using a rare earth group separation scheme has been used to measure ultratrace levels of rare earth elements (REE) in IAEA Human Hair (HH-1), IAEA Animal Bone (H-5), NBS Bovine Liver (SRM 1577), and NBS Orchard Leaf (SRM 1571) standards. The REE concentrations in Human Hair and Animal Bone range from 10^–8 g/g to 10^–11 g/g and their chondritic normalized REE patterns show a negative Eu anomaly and follow as a smooth function of the REE ionic radii. The REE patterns for NBS Bovine Liver and Orchard Leaf are identical except that their concentrations are higher. The similarity among the REE patterns suggest that the REE do not appear to be fractionated during the intake of biological materials by animals or humans.     

Reflections on 35 years of biological SRM production and analyses

Summary During the author's 39 years with the National Bureau of Standards (NBS)/National Institute for Standards and Technology (NIST) as an employee, and since then as Guest Researcher, he has been intimately involved with biological Standard Reference Material (SRM) production and analyses. His involvement with biological reference materials started with the very first biological certified reference material (CRM), the SRM 1571, Orchard Leaves, initiated in 1968 and issued in 1971, through the latest material (SRM 1575a, Pine Needles - renewal), issued in 2003. In addition, for more than 20 years he was Technical Coordinator for botanical SRMs for the NBS/NIST Analytical Chemistry Division. This paper contains his historical reflections and highlights from those years, and includes the techniques used to obtain and process these materials, new developments and procedures that resulted in vastly improved reference materials, the application of high accuracy neutron activation analysis to the certification of these standards, and the trace element quality assurance vital to the accuracy of these standards.     

Recent developments in NIST botanical SRMs

The National Institute of Standards and Technology (NIST) (formerly the National Bureau of Standards (NBS)) issued the first botanical reference material certified for elemental content in January 1971, as Standard Reference Material (SRM) 1571, Orchard Leaves. In the following years a total of nine additional botanical certified reference materials have been issued by NIST. Each of these materials was certified for major, minor and trace elements except for SRM 2695, certified for fluorine only. Botanical SRMs issued since 1991 are significantly improved over previous materials in a number of ways. Probably the most significant change is the use of a jet-milling process to grind them to extremely fine particles. This has resulted in botanical SRMs with significantly improved homogeneity. These NIST reference materials are described with information on homogeneity, drying techniques and grit content.     

Multielement photon activation analysis of biological materials.

A non-destructive photon activation procedure with 30-MeV bremsstrahlung followed by high-resolution γ-spectrometry is proposed for multielement analysis of biological materials. The materials tested were the NBS SRM Orchard Leaves and Bovine Liver, Bowen′s kale and Kentucky 1R1 tobacco standards. Simultaneous irradiation of the sample with synthetic multielement standards containing 25 elements showed that up to 12 elements can be determined in a single sample. The method is quite simple and gives good reproducible results. Agreement of the results with published data is excellent.     

Flow injection on-line dilution for multi-element determination in human urine with detection by inductively coupled plasma mass spectrometry

A simple flow injection on-line dilution procedure with detection by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of copper, zinc, arsenic, lead, selenium, nickel and molybdenum in human urine. Matrix effects were minimized by employing a dilution factor of 16.5 with on-line standard addition, and (103)Rh was used as internal standard to compensate for signal fluctuation. The procedure was validated by the analysis of two standard reference materials SRM 2670 (NIST) and Seronormtrade mark Trace Elements in Urine. Recovery experiments were performed by spiking the reference materials as well as artificial urine. The detection limits (mug l(-1)) were 0.12,0.96,0.30,0.09,0.45,0.08,0.09, and the precisions (RSD,%) were 2.6,2.3,3.0,3.7,3.7,4.9,2.8 for Cu, Zn, As, Pb, Se, Ni and Mo, respectively. The procedure was applied to the analysis of 41 human urine samples. No correlations between the concentrations of the elements were observed.     

Use of reference materials for quality control of elemental analysis by neutron activation with radiochemical separation

Summary This paper describes the use of certified reference materials to monitor the long-term quality of radiochemical separations. The practical limitations which determine the actual design of the quality control are discussed. The hypothesis that the high yield of the radiochemical separation will be constant with time has been checked and validated for the elements Zn, Fe, Co, Cd, Mo and to a lesser extent for W and Th using NBS SRM 1577A, BCR CRM 274 and IAEA RM A-11. This validation could not be made for the elements Cr, Au and Ag. Especially for Cr there is a serious lack of appropriate certified reference materials.     

Characterization of sediment reference materials by x-ray photoelectron spectroscopy

The chemical composition of surface layers of three sediment reference materials, Pond Sediment (Japan NIES CRM No. 2), River Sediment (US NBS SRM 1645) and Estuarine Sediment (US NBS SRM 1646), has been studied comparatively by X-ray photoelectron spectroscopy (XPS). The composition of River Sediment as determined by XPS is peculiar in that the concentration of Cr is much higher but that of Si is much lower than that expected from the bulk composition of the sample. This can be attributed to the structure of the sediment particles, which consist of silica-rich cores covered by surface layers rich in Cr(III). Organic substances are predominant in the surface layers of all three materials, as indicated by the C 1s and N 1s lines. The elemental composition of the surface layers can be reasonably related to the origin of the sediments. The bonding states of some elements in the sediment samples, deduced from the photoelectron binding energies, are briefly discussed.     

A highly selective diethyldithiocarbamate extraction system in activation analysis of copper,indium, manganese and zinc

A versatile separation system based on the extraction of dithiocarbamates and applicable to the determination of copper, managanese, zinc and indium in a wide selection of materials by activation analysis is described. After the dissolution of the sample and a few simple operations which eliminate specific interferences, depending upon the material (e. g. sodium and gold in the NBS Standard Reference Glasses), carbamates are extracted under specific conditions by addition of appropriate complexing agents and selective stripping. Extreme separation factors permit interference-free counting using a sodium iodide detector. For example, indium is separated from a hundred thousand fold excess of manganese in the determination of the two elements in Orchard Leaves. Results are also presented for all four elements in Bowen's Kale, NBS Bovine Liver, and for Cu, In and Mn in the 0.02 ppm and 1 ppm SRM glasses.     

Selective enrichment procedures for the determination of polychlorinated biphenyls and polycyclic aromatic hydrocarbons in environmental samples by gel permeation chromatography

An improved two-step clean up procedure involving alumina-silica column chromatography and gel permeation chromatography (GPC) of air particulate matter (NBS SRM 1648) and river sediment extracts and a GPC clean up procedure for marine biota samples are described for the determination of polycyclic aromatic hydrocarbons with two to five rings and selected polychlorinated biphenyl congeners, respectively. Bio-Beads SX-12 and SX-3 were used as packing materials. The recoveries obtained varied from 52 to 78% depending on the compound. Quantitative data for NBS SRM 1648 were comparable with those described previously for this sample.     

Determination of indium,copper and nickel in glassmaking materials and NBS standard reference materials by substoichiometric radioactivation analysis

The paper describes a method of radioactivation analysis for the determination of indium, copper and nickel. In the determination of indium, ordinary and displacement substoichiometries were applied for glassmaking materials while ordinary substoichiometry was applied for NBS standard reference materials. Copper and nickel in glassmaking materials and NBS standard reference materials were also determined by the displacement and ordinary substoichiometries. Indium contents in glassmaking materials by the two methods agreed with each other. The analytical results of indium, copper and nickel in NBS' SRM were also in good agreement with published values and certified values by NBS.     

The use of non-destructive high energy gamma photon activation for trace element survey analysis

An empirical study has been made of the potential of high energy γ photon activation and high resolution γ-ray spectrometry for the survey analysis of trace elements in a variety of materials. Human blood, urine, bone ash, standard glass (NBS, SRM 612) and air particulates, along with synthetic multi-element standards, have been studied following irradiation with γ photons of maximum energy 17–45 MeV. Elements found to be suited to determination by γ activation include Sb, As, Bi, Cd, Cs, Ca, Ce, Cr, Fe, Au, Pb, Mg, Mo, Ni, Nb, Rb, Sr, Tl, Ti, Tm, Zn and Zr. γ spectra, elemental concentrations measured, and/or limits of detection observed, for the matrices studied are given.     

Determination of Al, Cu, Li and Mn in spruce seeds and plant reference materials by slurry sampling graphite furnace atomic absorption spectrometry

An ultrasonic slurry sampling graphite furnace AAS method was developed for the determination of Al, Cu, Li and Mn in spruce seeds, NBS SRM 1575 pine needles and GBW CRM 07602 bush branches and leaves. The only sample preparation was grinding in a Mixer Mill before preparing a slurry by adding 0.14 mol/L nitric acid to a small sample aliquot. Cryogenic grinding was used for the spruce seeds to solve the problem of agglomerating during grinding at room temperature. A modified sample tray was applied allowing the use of both the commercial 1.5 mL vials and home-made 15 mL vials. With optimal conditions for ultrasonic agitation the homogeneity and particle size distributions in the slurries prepared in the two different vials were similar. Several aspects of the slurry sampling approach are discussed and data of important parameters are given, including the total number of particles injected into the graphite furnace, densities of the materials and percentage of analyte extracted into the liquid phase of the slurry. The density of the materials was determined by two methods; by using a Coulter particle analyser and by using a gravimetric method. The two methods gave similar accuracy and precision. The concentration ranges of the elements (in microg g(-1)) were: 80-2100 for Al, 3-15 for Cu, 0.06-2.5 for Li and 50-700 for Mn. External calibration with aqueous standards was employed. Chemical modifiers were not found to be necessary. The relative standard deviations were in the range 1.7-7%. Analyses of the two certified plant reference materials confirmed the accuracy of the method. In addition no significant difference was found for analyses of digested and slurried spruce seeds. The detection limit was 10 ng g(-1) for Li and 170 ng g(-1) for Cu. The characteristic mass (area measurements) was 4.4 pg for Li and 11 pg for Cu. For Al and Mn less sensitive wavelengths were used.     

Trace elemental composition of Nigerian coal measured by neutron activation analysis

The instrumental neutron activation analysis (INAA) technique has been used to determine 17 major, minor, and trace elements in samples of the three major sources of Nigerian coal. The NBS Standard Reference Material, Coal SRM 1632, was also analyzed, for the purpose of verifying the accuracy of the method. The results obtained with it were in good agreement with the NBS certified values. The concentrations of the major elements determined for the Nigerian coal were found to be much lower than the mean values of those reported for coal samples from other parts of the world.     

NBS activities in biological reference materials

Summary NBS activities in biological reference materials during 1986–1988 are described with a preview of plans for future certifications of reference materials. During the period, work has been completed or partially completed on about 40 reference materials of importance to health, nutrition, and environmental quality. Some of the reference materials that have been completed during the period and are described include: creatinine (SRM 914a), bovine serum albumin (SRM 927a), cholesterol in human serum (SRM's 1951–1952), aspartate aminotransferase (RM 8430), cholesterol and fat-soluble vitamins in coconut oil (SRM 1563), wheat flour (SRM 1567a), rice flour (SRM 1568a), mixed diet (RM 8431a), dinitropyrene isomers and 1-nitropyrene (SRM 1596), and complex PAH's from coal tar (SRM 1597). Oyster tissue (SRM 1566a) is being analyzed and should be available in 1988.

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NBS-Aktivitäten in biologischen Referenzmaterialien

     

Determination of noble metals in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry,following cloud point extraction

A simple separation procedure for noble metals based on cloud point extraction is proposed. The analyte ions in aqueous acidic solution, obtained by the acid digestion of the samples, were complexed with O,O-diethyl-dithiophosphate and Triton X-114 was added as a non-ionic surfactant. By increasing the temperature up to the cloud point, a phase separation occurs, resulting in an aqueous phase and a surfactant-rich phase containing most of the analytes that were complexed. The metals in the surfactant-rich phase were determined by electrothermal vaporization inductively coupled plasma mass spectrometry. The extraction conditions as well as the instrumental parameters were optimized. Enrichment factors ranging from 7 (Rh) to 60 (Pt) and limits of detection from 0.6 (Pt) to 3.0 ng l⁻¹ (Rh) were obtained in the digested samples. The extraction was not efficient for Ir. Among the reference materials analyzed in this work, only one (SRM 2670, urine) presented recommended values for Au and Pt. Due to the non-availability of adequate CRMs, accuracy was assessed by spiking known analyte amounts to the acid digests. Recoveries close to 100% were observed for all the studied elements but Ru. Poor agreement between found and recommended values was observed for non-digested urine sample, probably due to the carrier effect of co-extracted residual matrix components. However, good agreement was reached after urine acid mineralization.     

Precision Considerations in the Determination of Manganese in Mouse Brains by Furnace Atomic Absorption with Zeeman Background Correction

Abstract

A method is presented for the determination of manganese in mouse brains by furnace atomic absorption with Zeeman background correction. Precision for the method of standard additions is compared with that of aqueous calibration curves. NBS bovine liver SRM is analyzed to verify the accuracy of the method.     

Development of a 100 nmol mol<Superscript>−1</Superscript> propane-in-air SRM for automobile-exhaust testing for new low-emission requirements

New US federal low-level automobile emission requirements, for example zero-level-emission vehicle (ZLEV), for hydrocarbons and other species, have resulted in the need by manufacturers for new certified reference materials. The new emission requirement for hydrocarbons requires the use, by automobile manufacturing testing facilities, of a 100 nmol mol(-1) propane in air gas standard. Emission-measurement instruments are required, by federal law, to be calibrated with National Institute of Standards and Technology (NIST) traceable reference materials. Because a NIST standard reference material (SRM) containing 100 nmol mol(-1) propane was not available, the US Environmental Protection Agency (EPA) and the Automobile Industry/Government Emissions Research Consortium (AIGER) requested that NIST develop such an SRM. A cylinder lot of 30 gas mixtures containing 100 nmol mol(-1) propane in air was prepared in 6-L aluminium gas cylinders by a specialty gas company and delivered to the Gas Metrology Group at NIST. Another mixture, contained in a 30-L aluminium cylinder and included in the lot, was used as a lot standard (LS). Using gas chromatography with flame-ionization detection all 30 samples were compared to the LS to obtain the average of six peak-area ratios to the LS for each sample with standard deviations of <0.31%. The average sample-to-LS ratio determinations resulted in a range of 0.9828 to 0.9888, a spread of 0.0060, which corresponds to a relative standard deviation of 0.15% of the average for all 30 samples. NIST developed its first set of five propane in air primary gravimetric standards covering a concentration range 91 to 103 nmol mol(-1) with relative uncertainties of 0.15%. This new suite of propane gravimetric standards was used to analyze and assign a concentration value to the SRM LS. On the basis of these data each SRM sample was individually certified, furnishing the desired relative expanded uncertainty of +/-0.5%. Because automobile companies use total hydrocarbons to make their measurements, it was also vital to assign a methane concentration to the SRM samples. Some of the SRM samples were analyzed and found to contain 1.2 nmol mol(-1) methane. Twenty-five of the samples were certified and released as SRM 2765.