National Institute Of Standards And Technology SRM Research Articles

Visualization of differences in nanosecond laser ablation behavior for geological standard samples with different matrices

A combination of time-resolved shadowgraphy and laser-induced breakdown spectra (LIBS) was performed to investigate the ablation behavior of United States Geological Survey (USGS) and National Institute of Standards and Technology (NIST) geological standard samples when ablated by focused nanosecond laser pulses in air. The shock wave (SW) radius achieved 1535 μm at 743 ns for the BCR-2G, and 1513 μm at 759 ns for the NIST SRM 612 standard samples when a laser pulse energy of 17 mJ was used. The maximum speed, pressure, temperature, and density of the shock wave were 5435 m/s, more than 600 MPa, 3 × 105 K, and 7.76 kg/m3, respectively, for NIST SRM 612. Three SWs were generated as these standard samples were ablated. Laser-induced SWs are expected to contribute to attain an approximate matrix-matched reference material, which would render direct solid concentration analysis possible.

Photon activation analysis of NIST SRM sediment sample using the electron linear accelerator at Pohang Accelerator Laboratory

Photon activation analysis (PAA) of a sample of standard reference material 1646a (SRM 1646a) sediment sample was carried out using the electron linear accelerator (LINAC) at Pohang Accelerator Laboratory (PAL). A method is presented for the simultaneous determination of Sc, Mn, and Zr by PAA using all elements and sediment SRM 1646a as internal standards. The results show good agreement with the values given by the National Institute of Standards and Technology (NIST). However, a large amount of Zr in SRM 1646a was discovered, which was not in the NIST certificate.

Determination of Pb in glasses by direct solid sampling and high-resolution continuum source graphite furnace atomic absorption spectrometry: method development and analyses of glass samples

In this study, a new method was developed for the determination of Pb in glass samples by solid sampling graphite furnace atomic absorption spectrometry (SS GFAAS), and Pb concentrations of two glass samples were determined. For method development, the National Institute of Standards and Technology (NIST) SRM 612 glass standard was used. Different experimental and instrumental parameters were investigated, including sample mass introduced into the graphite furnace, use of a modifier, use of an aqueous standard solution for calibration curves, and different detection wavelengths. Pd(NO3)2+Mg(NO3)2 was used as a modifier for experiments. LOD values were 201.6pg Pb at 205.328nm with 3pixels (central pixel±1) and 11.2pg Pb at 283.060nm with 3pixels (central pixel±1). Then, Pb concentrations in two different glass samples were determined by SS GFAAS using aqueous Pb standard and solid standard (NIST SRM 612) for calibration. Thus, the study shows that SS GFAAS is a reliable method for the determination of Pb in glass samples with the advantageous using very small amount (30–100μg) of glass sample and no need to dissolve the glass by toxic and hazardous chemicals.

Simultaneous determination of thirteen organophosphate esters in settled indoor house dust and a comparison between two sampling techniques

An analytical method for the simultaneous determination of 13 organophosphate esters (OPEs) in house dust was developed. The method is based on solvent extraction by sonication, sample cleanup by solid phase extraction (SPE), and analysis by gas chromatography–positive chemical ionization–tandem mass spectrometry (GC/PCI–MS/MS). Method detection limits (MDLs) ranged from 0.03 to 0.43μg/g and recoveries from 60% to 118%. The inter- and intra-day variations ranged from 3% to 23%. The method was applied to dust samples collected using two vacuum sampling techniques from 134 urban Canadian homes: a sample of fresh or “active” dust (FD) collected by technicians and a composite sample taken from the household vacuum cleaner (HD). Results show that the two sampling methods (i.e., FD vs HD) provided comparable results. Tributoxyethyl phosphate (TBEP), triphenyl phosphate (TPhP), tris(chloropropyl) phosphate (TCPP), tri(2-chloroethyl) phosphate (TCEP), tris(dichloro-isopropyl) phosphate (TDCPP), tricresyl phosphate (TCrP), and tri-n-butyl phosphate (TnBP) were detected in the majority of samples. The most predominant OPE was TBEP, with median concentrations of 31.9μg/g and 22.8μg/g in FD and HD samples, respectively, 1 to 2 orders of magnitude higher than other OPEs. The method was also applied to the analysis of OPEs in the National Institute of Standards and Technology (NIST) standard reference material (NIST SRM 2585, organic contaminants in house dust). The results from SRM 2585 may contribute to the certification of OPE concentration values in this SRM.

Determination of low‐level (sub‐microgram) sulfur concentrations by isotope dilution multi‐collector inductively couple plasma mass spectrometry using a 33S spike and internal normalization for mass bias correction

The certification of sulfur (S) in Standard Reference Materials™ by the National Institute of Standards and Technology (NIST) has been exclusively performed using isotope dilution thermal ionization mass spectrometry (ID-TIMS). The ID-TIMS measurement method is limited in its capability for low concentration measurements (<1 µg/g) due to the blank associated with the chemical reduction procedure (≈0.2 S µg). Newly developed materials and applications, such as biofuels made from soy and nanomedicine, pose a challenge to the ID-TIMS technique because of their very low concentrations (<<1 µg/g) of S. As described here, a measurement technique with low S blanks is essential for low-level S measurements. An isotope dilution (ID) multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) method combined with an internal normalization approach for mass bias correction has been used to determine low-level S concentrations in synthetically prepared mixtures using a (33)S-enriched spike material. Dilute sulfur solutions (1 µg S/g) were prepared from NIST SRM 3154 (Sulfate Spectrometric Solution) to test the capability of this technique for measuring very low-level S concentrations. The concentration results for each solution were 0.983 ± 0.004 µg/g (95% CI, n = 2, k = 2), 1.006 ± 0.005 µg/g (95% CI, n = 2, k = 2), and 0.999 ± 0.003 µg/g (95% CI, n = 2, k = 2), in excellent agreement with the gravimetric determination, deviating less than 0.35% and suggesting the technique can yield unbiased and accurate results. The blanks averaged 13 ± 0.0017 ng S (1s). The data results provide a clear indication that the ID-MC-ICP-MS method for the determination of low-level S concentrations is feasible. The more than one order of magnitude reduction of the blanks suggests that it is a better alternative to the ID-TIMS method for very low S materials such as are encountered in biofuels and some biochemical species. Published 2012. This article is a US Government work and is in the public domain in the USA.

Vitamin D status as an international issue: National surveys and the problem of standardization

Wide spread variation in measurement results of total 25-hydroxyvitamin D (25(OH)D) confounds international efforts to develop evidence-based clinical guidelines. Accordingly, NIH Office of Dietary Supplements (ODS) in collaboration with CDC National Center for Environmental Health (NCEH), National Institute of Standards and Technology (NIST) and Ghent University established the Vitamin D Standardization Program (VDSP) in November 2010. VDSP objectives include: (1) standardize 25(OH)D concentration measurements in national health surveys around the world, (2) evaluate survey differences, (3) extend standardization efforts to assay manufacturers, and to clinical, commercial, and research laboratories, (4) promote standardization of emerging metabolites of vitamin D status, and (5) enable the use of standardized data in patient care and public health. An interlaboratory comparison study is being conducted to assess measurement variability among current assays. Participants include national health surveys from Australia, Canada, Germany, Ireland, Mexico, South Korea, UK and USA, 15 assay manufacturers, and two external quality assurance programs. CDC will implement a formal laboratory certification program. Standardization activities will use single-donor, fresh-frozen serum collected using the CLSI C37 protocol. Initial assay performance criteria, based on biological variability data, are ≤10 % imprecision and ≤5 % bias in relation to the reference values. An ancillary study on commutability of NIST SRM 972a, external quality assurance testing materials is included. To increase the comparability of existing data from different national surveys, master equations will be developed to facilitate the conversion of already existing national survey data to the NIST-Ghent University reference measurement procedures.

Results of the recalibration of creatinine measurement with the modular Beckman Coulter® Jaffe creatinine method

Serum creatinine is important for detecting the beginning of a decline in kidney function. The Beckman Coulter Jaffe reagents for measuring creatinine have been standardized to the internationally accepted reference method: isotope dilution mass spectrometry (IDMS). The impact of this recalibration on the Beckman Coulter modular or cup (stat) Jaffe method is studied. Recalibrated Jaffe (calibrator set points IDMS traceable) and classic National Institute of Standards and Technology (NIST) creatinine methods (traceable to NIST 914a) were compared with an enzymatic method (Sentinel, traceable to NIST SRM 967). All measurements were performed on Synchron DxC 800 systems. Imprecision of the routine methods was studied using the Clinical and Laboratory Standards Institute (CLSI) protocols and laboratory quality survey. Thirteen plasma pools, with concentrations < 354 mmol/L, were analyzed with a gas chromatography isotope dilution mass spectrometry (GC-IDMS) method and routine methods. Total error of 8.2% based on biological variability, set on the GC-IDMS values and acceptance criteria (bias < 5%, imprecision < 8% at concentrations ≥ 88.4 mmol/L and a maximum 10% increase in the relative error of estimated glomerular filtration rate (eGFR) of the National Kidney Disease Educational Program (NKDEP) were used for evaluating analytical performance of the routine methods studied. After recalibration of the Jaffe method, median bias (mmol/L) decreased from 12.4 (95% CI: 9.1-21.2) to 7.3 (95% CI: 1.5-10.5). Imprecision of the Jaffe method is in agreement with the claim of the manufacturer, namely < 9 mmol/L or < 3% below or above 292 mmol/L. Below creatinine of 88.4 mmol/L, imprecision of the recalibrated Jaffe and enzymatic methods is between 4.1% and 6.9%, and 5.0% and 7.1%, respectively, and significantly different (p = 0.02 for both the Jaffe and enzymatic methods) from the goal, based on biological variability, of 2.7%. For the adult pools, all recalibrated Jaffe and enzymatic results fall within the total error of 8.2%. In the pediatric samples, one-third of the recalibrated Jaffe and three of the six enzymatic results fall within this total error goal. Recalibration significantly reduced bias of the Jaffe method. For pediatric samples, recalibrated Jaffe results do not comply with either the imprecision goal or the total error based on biological variability. Adult recalibrated Jaffe results are in compliance with the goals based on biological variability and with the acceptance criteria from the NKDEP.

NHANES Monitoring of Serum 25-Hydroxyvitamin D: A Roundtable Summary1–3

A roundtable to discuss monitoring of serum 25-hydroxyvitamin D [25(OH)D] in the NHANES was held in late July 2009. Topics included the following: 1) options for dealing with assay fluctuations in serum 25(OH)D in the NHANES conducted between 1988 and 2006; 2) approaches for transitioning between the RIA used in the NHANES between 1988 and 2006 to the liquid chromatography tandem MS (LC-MS/MS) measurement procedure to be used in NHANES 2007 and later; 3) approaches for integrating the recently available standard reference material for vitamin D in human serum (SRM 972) from the National Institute of Standards and Technology (NIST) into the NHANES; 4) questions regarding whether the C-3 epimer of 25-hydroxyvitamin D3 [3-epi-25(OH)D3] should be measured in NHANES 2007 and later; and 5) identification of research and educational needs. The roundtable experts agreed that the NHANES data needed to be adjusted to control for assay fluctuations and offered several options for addressing this issue. The experts suggested that the LC-MS/MS measurement procedure developed by NIST could serve as a higher order reference measurement procedure. They noted the need for a commutability study for the recently released NIST SRM 972 across a range of measurement procedures. They suggested that federal agencies and professional organizations work with manufacturers to improve the quality and comparability of measurement procedures across all laboratories. The experts noted the preliminary nature of the evidence of the 3-epi-25(OH)D3 but felt that it should be measured in 2007 NHANES and later.

A Compilation of New and Published Major and Trace Element Data for NIST SRM 610 and NIST SRM 612 Glass Reference Materials

Microanalytical trace element techniques (such as ion probe or laser ablation ICP‐MS) are hampered by a lack of well characterized, homogeneous standards. Two silicate glass reference materials produced by National Institute of Standards and Technology (NIST), NIST SRM 610 and NIST SRM 612, have been shown to be homogeneous and are spiked with up to sixty one trace elements at nominal concentrations of 500 μg g‐1 and 50 μg g‐1 respectively. These samples (supplied as 3 mm wafers) are equivalent to NIST SRM 611 and NIST SRM 613 respectively (which are supplied as 1 mm wafers) and are becoming more widely used as potential microanalytical reference materials. NIST however, only certifies up to eight elements in these glasses. Here we have compiled concentration data from approximately sixty published works for both glasses, and have produced new analyses from our laboratories. Compilations are presented for the matrix composition of these glasses and for fifty eight trace elements. The trace element data includes all available new and published data, and summaries present the overall average and standard deviation, the range, median, geometric mean and a preferred average (which excludes all data outside ± one standard deviation of the overall average). For the elements which have been certified, there is a good agreement between the compiled averages and the NIST data. This compilation is designed to provide useful new working values for these reference materials.

Determination of Boron in Plants and Plant-Derived Foods by Ultrasonic Nebulization-Inductively Coupled Plasma Atomic Emission Spectrometry with Addition of Mannitol

Abstract An ultrasonic nebulization-inductively coupled plasma (ICP) atomic emission spectrometry procedure was developed to determine boron in plants and plant-derived foods. Samples were ashed at 550°C for 4 h, and the resulting ash was dissolved into a mannitol-nitric acid solution to form a boron- mannitol complex. Solutions were directly nebulized into ICP by an ultrasonic nebulizer. The memory effect—the main drawback for determining boron with the ultrasonic nebulizer—was minimized with addition of mannitol. Two National Institute of Standards and Technology (NIST) standard reference materials (SRM 1515 apple leaves and SRM 1547 peach leaves) and 25 food and plant materials spiked with NIST SRM 1515 were analyzed to verify method accuracy. Boron contents found in NIST standard samples were in excellent agreement with certified values. A detection limit (2σ) of 0.5 μg/L and typical recoveries of 93 to 106% from spiked selected samples were obtained.

The application of instrumental neutron activation analysis for the certification of the new NIST Fly Ash SRM

The National Institute of Standards and Technology (NIST) recently released the second renewal of its “Trace Elements in Coal Fly Ash” Standard Reference Material (SRM 1633b). This new material is currently certified for 23 major, minor and trace elements, and concentrations of an additional 24 elements are provided for “information only” purposes. Current plans are to certify the concentrations of a number of rare earths upon completion of additional analytical work now in progress. Instrumental neutron activation analysis (INAA) has played a major role in the certification of this new material in view of its potential for accuracy, multielemental capability, ability to assess homogeneity, high sensitivity for many elements, and essentially blank-free nature. For an element to be certified in a NIST SRM its concentration is usually determined by at least two independent analytical techniques. INAA has provided analytical information for 15 of the 23 elements certified, as well as for 22 of the 24 elements listed for “information only”. In addition, INAA has provided much of the homogeneity information for this SRM. This paper will describe these analytical procedures, and highlight those designed to optimize and assess the accuracy of the INAA measurements.

Sequential injection analysis system for the determination of hydride-forming elements by direct current plasma atomic emission spectrometry

A method for the determination of volatile hydride-forming elements with direct current plasma atomic emission spectrometry (DCP-AES) based on a modified version of the sequential injection analyser has been developed. The sequential injection (SI) hydride generator consists of two multi-port valves and a piston burette. The burette is also used as a dynamic reaction chamber the volume of which can be changed by the piston movement. This arrangement allows isobaric reaction. The burette also functions as a gas–liquid separator where the liquid reaction products are drained via a channel through the piston head. The hydride gases are pumped by the piston into the plasma through a thin quarts capillary, which is also used to position the direction of gas flow to the centre of the plasma. All functional parts in this system are computer controlled. The performance of the SI hydride generation DCP-AES system has been tested in the determination of arsenic, bismuth and germanium. The detection limits (3s) were 0.15, 0.08 and 0.03 µg l–1, respectively. The calibration graphs were linear (r >0.999) in the concentration ranges studied: 0–50 µg l–1 for arsenic and 0–10 µg l–1 for bismuth and germanium. The relative standard deviation for all three elements was less than 10% at a concentration level of 1 µg l–1 and ≈3% at the 10 µg l–1 level. The accuracy of the method was tested in the determination of arsenic in the National Institute of Standards and Technology (NIST) Standard Reference Materials, NIST SRM 1573 Tomato Leaves and NIST SRM 1575 Pine Needles.

Certification of a new NIST fly ash standard reference material

In June 1993 the National Institute of Standards and Technology (NIST) released the third version of “Constituent Elements in Coal Fly Ash” Standard Reference Material (SRM 1633b). This material is intended for quality assurance purposes in evaluating the analytical methods used for the determination of constituent elements in coal fly ash or in materials with similar matrices. It has been certified for 23 major, minor and trace elements using ten different analytical techniques. For an element to be certified in a NIST SRM, its concentration is usually determined by at least two independent analytical techniques. The concentrations of additional 24 elements are provided for “information only” purposes in the new fly ash. Current plans are to certify the concentrations of a number of rare earths upon completion of additional analytical work now in progress. Homogeneity testing was accomplished using instrumental neutron activation analysis and X-ray fluorescence. This presentation summarizes the preparation of this new material and the analytical results used for certification.