New NIST sediment SRM for inorganic analysis

NIST maintains a portfolio of more than 1300 standard reference materials (SRM), more than a third of these relating to measurements in the biological and environmental fields. As part of the continuous renewal and replacement efforts, a set of new marine sediments has been recently developed covering organic and inorganic determinations. This paper describes the steps taken in sample preparation, homogeneity assay, and analytical characterization and certification with specific emphasis on SRM 2702 inorganics in marine sediment. Neutron activation analysis showed the SRM to be highly homogeneous, opening the possibility for use with solid sampling techniques. The certificate provides certified mass fraction values for 25 elements, reference values for eight elements, and information values for 11 elements, covering most of the priority pollutants with small uncertainties of only several percent relative. The values were obtained by combining results from different laboratories and techniques using a Bayesian statistical model. An intercomparison carried out in field laboratories with the material before certification illustrates a high commutability of this SRM.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Multielement analysis of NIST proposed SRM 1547 Peach Leaves

The k₀-standardization method of neutron activation analysis was applied for the multielement analysis of the NIST (National Institute of Standards and Technology) proposed Standard Reference Material (SRM) No. 1547 Peach Leaves. At the moment, 50 elements can be determined from a one day irradiation, using the TRIGA Mark II reactor of the Joef Stefan Institute, Ljubljana. Among them, 28 elements were determined quantitatively, and for the remaining 22 elements, less than values were obtained.     

Isotopic analysis of uranium in NIST SRM glass by femtosecond laser ablation MC-ICPMS

We employed femtosecond Laser Ablation Multicollector Inductively Coupled Mass Spectrometry for the determination of uranium isotope ratios in a series of standard reference material glasses (NIST 610, 612, 614, and 616). The uranium in this series of SRM glasses is a combination of isotopically natural uranium in the materials used to make the glass matrix and isotopically depleted uranium added to increase the uranium elemental concentration across the series. Results for NIST 610 are in excellent agreement with literature values. However, other than atom percent ²³⁵U, little information is available for the remaining glasses. We present atom percent and isotope ratios for ²³⁴U, ²³⁵U, ²³⁶U, and ²³⁸U for all four glasses. Our results show deviations from the certificate values for the atom percent ²³⁵U, indicating the need for further examination of the uranium isotopes in NIST 610-616.     

Long-term stability of hydrocarbons in NIST gas standard reference material (SRM) 1800

A gas standard reference material (SRM) containing fifteen hydrocarbons in nitrogen at a nominal 5 nmol mol(-1) was issued in 1993. The certification period for SRM 1800 was assigned as 2 years, because of limited stability data. Over a period of 10 years reanalysis of the lot standard (a sample chosen from the SRM lot to which all other lot samples are compared), SRM samples remaining in stock for sale, and SRMs returned to the National Institute of Standards and Technology (NIST) for recertification, were compared with primary standards to assess the stability of the hydrocarbons. New primary standards were periodically introduced into the original primary standard suite to assess the stability and consistency of the primary standards. Over this ten-year period 11 SRM 1800 samples were reanalyzed, resulting in 210 amount-of-substance fraction (concentration) determinations performed for quality-assurance purposes. Of these measurements 209 (99.5%) agreed within the original 95% confidence interval of the +/-4% expanded uncertainty, demonstrating the stability of the standards. There was also agreement to within +/-2% of the original concentration for 204 (97%) of the measurements. This is well within the original +/-4% expanded uncertainty assigned to the hydrocarbon concentrations at the approximate 95% confidence interval demonstrating stability. These results will enable the expiry date to be increased for future restock issues of SRM 1800.     

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.     

Characterization of NIES CRM No. 23 Tea Leaves II for the determination of multielements

A candidate environmental certified reference material (CRM) for the determination of multielements in tea leaves and materials of similar matrix, NIES CRM No. 23 Tea Leaves II, has been developed and characterized by the National Institute for Environmental Studies (NIES), Japan. The origin of the material was tea leaves, which were ground, sieved through a 106-μm mesh, homogenized, and then subdivided into amber glass bottles. The results of homogeneity and stability tests indicated that the material was sufficiently homogeneous and stable for use as a reference material. The property values of the material were statistically determined based on chemical analyses by a network of laboratories using a wide range of methods. Sixteen laboratories participated in the characterization, and nine certified values and five reference values were obtained. These property values of the candidate CRM, which are expressed as mass fractions, were close to the median and/or mean values of the mass fractions of elements in various tea products. The candidate CRM is appropriate for use in analytical quality control and in the evaluation of methods used in the analysis of tea and materials of similar matrix.     

Characterization of NIST food-matrix standard reference materials for their vitamin C content

The vitamin C concentrations in three food-matrix Standard Reference Materials (SRMs) from the National Institute of Standards and Technology (NIST) have been determined by liquid chromatography (LC) with absorbance detection. These materials (SRM 1549a Whole Milk Powder, SRM 1849a Infant/Adult Nutritional Formula, and SRM 3233 Fortified Breakfast Cereal) have been characterized to support analytical measurements made by food processors that are required to provide information about their products’ vitamin C content on the labels of products distributed in the United States. The SRMs are primarily intended for use in validating analytical methods for the determination of selected vitamins, elements, fatty acids, and other nutrients in these materials and in similar matrixes. They can also be used for quality assurance in the characterization of test samples or in-house control materials, and for establishing measurement traceability. Within-day precision of the LC method used to measure vitamin C in the food-matrix SRMs characterized in this study ranged from 2.7 % to 6.5 %.     

Characterization of the NIST shellfish Standard Reference Material 4358

A new shellfish Standard Reference Material 4358 was developed by the National Institute of Standards and Technology through an international interlaboratory comparison that involved twelve laboratories-participants from nine countries. The results from the participants were statistically evaluated, and the most robust certified values were based on the median of laboratories’ reported means and the uncertainties derived using the bootstrap method. Massic activity certified values were established for fourteen radionuclides, five activity ratios, and informational massic activity values for eight more radionuclides and two activity ratios.     

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

Journal of Radioanalytical and Nuclear Chemistry - Photon activation analysis (PAA) of a sample of standard reference material 1646a (SRM 1646a) sediment sample was carried out using the...     

Definitive method certification of clinical analytes in lyophilized human serum: NIST Standard Reference Material (SRM) 909b

The National Institute of Standards and Technology (NIST) has developed several Standard Reference Materials (SRMs) based on human serum. NIST SRM 909b, Human Serum, is a lyophilized human serum material with concentrations for seven organic and six inorganic analytes at two levels certified solely by definitive methods (DMs). This material provides the vehicle by which high precision, high accuracy measurements made with DMs at NIST can be transferred through the measurement hierarchy to other laboratories. Isotope dilution gas chromatographic-mass spectrometric (GC-IDMS) methods were applied to measure cholesterol, creatinine, glucose, urea, uric acid, triglycerides, and total glycerides. Thermal ionization isotope dilution mass spectrometry (TI-IDMS) was used for determination of lithium, magnesium, potassium, calcium, and chloride. In addition, chloride was determined by coulometry, providing a comparison between two DMs. Sodium, which lacks a stable isotope that would permit isotope dilution mass spectrometric (IDMS) measurement, was determined by gravimetry. SRM 909b includes certified values for total glycerides and triglycerides, which were not certified in the previous lot of this material (SRM 909a). Improvement in uniformity of vial fill weight in the production of SRM 909b resulted in smaller certified uncertainties over previous freeze-dried serum SRMs. Uncertainties at the 99% level of confidence for relative expanded uncertainty (%) for certification of the organic analytes on a mmol/L/g basis ranged from 0.44% for urea (level II) to 5.04% for glucose (level II). (In-house studies have shown glucose to be a relatively unstable analyte in similar lyophilized serum materials, degrading at about 1% per year.) Relative expanded uncertainties (99% C.I.) for certification of inorganic analytes on a mmol/L/g basis ranged from 0.25% for chloride (level I) to 0.49% for magnesium (level II).     

Contents of selected B vitamins in NIST SRM 3280 multivitamin/multielement tablets by liquid chromatography isotope dilution mass spectrometry

There is increased interest in accurately assessing the total dietary intake of vitamins from all sources, including foods and dietary supplements. Consequently, a Dietary Supplement Ingredient Database (DSID), based upon analytical values, is being established by USDA with support of the Office of Dietary Supplements (ODS), NIH. The DSID necessitated the development of a new SRM, 3280 — Multivitamin/Multimineral Tablets, by the National Institute of Standards and Technology (NIST), with support from the ODS. As a continuation of a long-term project to develop and validate new methods of determining water-soluble B vitamins in foods and dietary supplements, and as part of a collaborative effort with NIST to characterize SRM 3280, values for the vitamin contents of SRM 3280 have been generated by a liquid chromatographic isotope dilution mass spectrometric (LC/IDMS) method. Isotope-labeled (¹³C and/or ²H) B vitamins (B1-thiamine, B6-pyridoxine, B3-nicotinamide, and B5-pantothenic acid) were obtained from commercial sources, with the support of the ODS/NIH. Our LC/IDMS method uses a C18 reversed phase column, an Agilent 1100 HPLC system, and a Quattro Micro triple-quad mass spectrometer (MS). B vitamin determination was achieved using a gradient LC profile combined with MS/MS detection in multiple reaction monitoring mode. Stock solutions of the isotope-labeled vitamins were calibrated against USP standard solutions. The SRM tablets, with added amounts of the four isotope-labeled B vitamins, were extracted and the vitamins simultaneously determined in a single LC run, in contrast with the single-component determinations performed via IDMS. Unknown vitamin concentrations were calculated by comparing the ratios of the integrated LC peaks at the different masses of the unlabeled and labeled vitamins.     

Definitive method certification of clinical analytes in lyophilized human serum: NIST Standard Reference Material (SRM) 909b

The National Institute of Standards and Technology (NIST) has developed several Standard Reference Materials (SRMs) based on human serum. NIST SRM 909b, Human Serum, is a lyophilized human serum material with concentrations for seven organic and six inorganic analytes at two levels certified solely by definitive methods (DMs). This material provides the vehicle by which high precision, high accuracy measurements made with DMs at NIST can be transferred through the measurement hierarchy to other laboratories. Isotope dilution gas chromatographic-mass spectrometric (GC-IDMS) methods were applied to measure cholesterol, creatinine, glucose, urea, uric acid, triglycerides, and total glycerides. Thermal ionization isotope dilution mass spectrometry (TI-IDMS) was used for determination of lithium, magnesium, potassium, calcium, and chloride. In addition, chloride was determined by coulometry, providing a comparison between two DMs. Sodium, which lacks a stable isotope that would permit isotope dilution mass spectrometric (IDMS) measurement, was determined by gravimetry. SRM 909b includes certified values for total glycerides and triglycerides, which were not certified in the previous lot of this material (SRM 909a). Improvement in uniformity of vial fill weight in the production of SRM 909b resulted in smaller certified uncertainties over previous freeze-dried serum SRMs. Uncertainties at the 99% level of confidence for relative expanded uncertainty (%) for certification of the organic analytes on a mmol/L/g basis ranged from 0.44% for urea (level II) to 5.04% for glucose (level II). (In-house studies have shown glucose to be a relatively unstable analyte in similar lyophilized serum materials, degrading at about 1% per year.) Relative expanded uncertainties (99% C.I.) for certification of inorganic analytes on a mmol/L/g basis ranged from 0.25% for chloride (level I) to 0.49% for magnesium (level II). Received: 30 July 1997 / Revised: 24 October 1997 / Accepted: 31 October 1997     

NAA of two deep sea manganese nodule RMs for multielements

Mn-nodule is one of the most important deep sea mineral resources to be explored and exploited in the next century. Analytical quality control based on this kind of Certified Reference Materials (CRMs) is therefore necessay. In the present work, nearly 30 elements in two Chinese Mn nodule Reference Materials (RMs), GSPN-2 and GSPN-3, were determined using extendedK ₀-relative comparison NAA technique, developed in our laboratory. The unique features of this work include; (1) high accuracy obtained by the interal validation function of our technique; (2) extensive determinable elements obtained by the hybrid nature of our software and (3) neutron flux self-shielding corrections.     

Characterization and use of the new NIST rapid pneumatic tube irradiation facility

Recently a new rapid pneumatic tube facility was inserted into a long unused location in the NIST 20 MW nuclear reactor. This facility was designed and constructed specifically for rapid INAA using short lived activation products. Included is a computer controlled console which uses fast sensors to accurately measure the irradiation capsule flight time, and a loss-free counting system connected to a 32% efficient PHGe detector with a transistor reset preamplifier. Measurement of travel, times from end-of-irradiation to detector were 473±8 ms. Measurement of the thermal neutron fluence rate was 5.0·10¹³ n·cm⁻²·s⁻¹. The other three pneumatic tubes in the NIST reactor have transfer times of 3 to 15 seconds, and no timing capability more accurate than human response. This new facility substantially improves our ability to accurately determine activation products with half-lives from 1 to 100 seconds. Characterization information reported on this new irradiation facility includes absolute fluence measurements, fluence rate variations within the capsule and variations with time, and determination of analytical sensitivities for fluorine-20 selenium-77m, and silver-110g.     

Microwave digestion of "residual fuel oil" (NIST SRM 1634b) for the determination of trace elements by inductively coupled plasma-mass spectrometry

A microwave procedure for the digestion of the NIST 1634b reference material "residual fuel oil" in closed pressurized vessels was developed in an attempt to facilitate routine analysis and obtain reproducible conditions or comparable results. The influence of sample size, reagent composition and volume, microwave power, and duration of heating on the digestion procedure was studied. Pressure and temperature inside the reaction vessels were monitored to determine the progression of the reaction and to develop optimal conditions. A nine-step heating program requiring 36.5 min with microwave power not exceeding 450 W in the pulsed mode was found suitable for the digestion of approximately 250 mg fuel oil with a mixture of nitric acid (5.0 mL) and hydrogen peroxide (2.0 mL). The reproducibility of microwave power was determined in terms of the relative standard deviations (n = 3) for temperature (2.7%) and pressure (4.9%) data. The vapor pressures obtained with 5.0 mL Milli-Q water (heated) in an 80-mL digestion vessel showed good agreement with literature data. The excess acid in the resulting digests was removed by evaporation and the concentrations of 24 elements (Ag, Al, As, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mo, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V, U, and Zn) were determined in the diluted digests by inductively coupled plasma mass spectrometry (ICP-MS). The experimental results were in good agreement with the certified and recommended concentrations for eight elements (Al, As, Co, Cr, Ni, Pb, V, Zn) in solutions obtained after one digestion step. An additional digestion step, consisting of intermediate cooling and venting stages, was required for the accurate determination of Fe. No agreement was reached for Ca and Ba even after two-step digestion. The proposed method of digestion provided precise results with relative standard deviations generally less than 5% for most of the elements determined.     

Characterization (certification) of Corn Bran (NIST RM 8433), Corn Starch (NIST RM 8432) and Microcrystalline Cellulose (NIST RM 8416) Reference Materials for essential and toxic major, minor and trace elemental constituents

Summary Corn Bran (NIST RM 8433), Corn Starch (NIST RM 8432) and Microcrystalline Cellulose (NIST RM 8416) Reference Materials were characterized for essential and toxic major, minor and trace elemental composition in an interlaboratory cooperative characterization campaign. Extensive application of widely varied analytical methods by analysts in cooperating laboratories yielded 10–29 best estimate and 1–16 informational concentration values for each of these materials. Two materials, Corn Starch and Microcrystalline Cellulose, contain particularly low levels of trace elements. These reference materials are intended for analytical quality control of elemental determinations in corn and plant products as well as other agricultural/food materials with related matrices.Contribution No. 92–146 from Centre for Land and Biological Resources Research     

Characterization (certification) of Bovine Muscle Powder (NIST RM 8414), Whole Egg Powder (NIST RM 8415) and Whole Milk powder (NIST RM 8435) Reference Materials for essential and toxic major, minor and trace element constituents

Summary Bovine Muscle Powder (NIST RM 8414), Whole Egg Powder (NIST RM 8415) and Whole Milk Powder (NIST RM 8435) Reference Materials were characterized for essential and toxic major, minor and trace element composition in an interlaboratory cooperative characterization campaign. Extensive application of widely varied analytical methods yielded best estimate concentration values for 27, 23 and 21 elements, and informational concentration values for 5, 4 and 9 elements, respectively, in RM's 8414, 8415 and 8435. These Reference Materials are intended for analytical quality control of element determinations on meat, egg and milk-based products as well as agricultural/food materials with related matrices.Contribution no. 92–147 from Centre for Land and Biological Resources Research     

电感耦合等离子体质谱测定地质样品中多种元素

用电感耦合等离子体质谱(ICP-MS)测定了地质样品中多种元素。考察了测量过程中的基体效应及质谱干扰,利用In内标,补偿由于基体效应的影响所引起的测量偏差,建立校正公式校正质谱干扰。方法的检出限为0.06~250ng/L,精密度为1.7%~3.2%,加标回收率为91%~108%,方法适于批量地质样品分析。