Investigation of chromium(III) acetylacetonate as a calibration reference material for atomic absorption spectroscopy

It is shown that chromium(III) acetylacetonate meets the requirements of calibration reference materials: it is homogeneous, soluble in water and organic solvents, and its solutions are stable. Chromium(III) acetylacetonate has been successfully used as a calibration reference material in the analysis of chromium in iron-base alloys. The procedure involves chromium acetylacetonate extraction using methyl isobutyl ketone followed by direct atomic absorption analysis of the organic extract. The detection limit of the procedure is 10 ng g⁻¹. Correspondence: Konstantin Belikov, State Scientific Institution “Institute for Single Crystals” of the National Academy of Sciences of Ukraine, Kharkov, Ukraine     

Mercury species immobilized on sulphydryl cotton: A new candidate reference material for mercury speciation

A batch of sulphydryl cotton microcolumns was prepared and charged with a mixed Hg standard solution (methyl-, ethyl- and inorganic Hg, 10 g l^–1 as Hg, 3 ml) and stored at 4 °C in a light-tight box. At regular time intervals over a 4 month period microcolumns were removed and Hg species were quantified by gas chromatography microwave-induced plasma atomic emission spectrometry (after elution, extraction and derivatization steps). It was found that analyte recoveries for methyl- and inorganic Hg were quantitative over the 4 month period while ethyl-Hg species appeared to be stable for up to 2 months.     

Preparation and certification of a reference material for the determination of nutrients in seawater

There is an urgent need for natural water reference materials certified for nutrients. In 1996, NRC collected seawater for a proposed CRM at a depth of 200 m in the North Atlantic; this was immediately filtered through 0.05-m cartridge filters into 50-L carboys. The water was later homogenized in the NRC laboratories in Ottawa and stabilized via gamma irradiation. Over six years of stability testing no significant deterioration was detected. In addition to the usual customary standard colorimetric procedures, alternative analytical methods were developed to enable the certification process. The production of a CRM called MOOS-1 will be discussed. Certified values, with uncertainty components addressing the homogeneity, stability, and characterization of the material, were calculated to be: orthophosphate=1.56±0.07 µmol L^–1, silicate=26.0±1.0 µmol L^–1, nitrite=3.06±0.15 µmol L^–1, and nitrite and nitrate=23.7±0.9 µmol L^–1.     

Development of a new standard reference material: SRM 1955 (homocysteine and folate in human serum)

Total homocysteine (tHCY) and folate are interrelated biomarkers for arteriosclerosis and coronary heart disease. Although many different methods for both tHCY and folate are clinically available, the intermethod and interlaboratory results are often poor, resulting in the need for a matrix reference material and reference methods. The National Institute of Standards and Technology (NIST) has developed isotope dilution liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/ tandem mass spectrometry (LC/MS/MS) methods for determination of tHCY and several folate forms including 5-methyltetrahydrofolic acid (5MT) and folic acid (FA). Additionally, a method for simultaneous measurement of tHCY, 5MT, and FA has been developed and validated. In collaboration with the Centers for Disease Control and Prevention (CDC), mass spectrometric methods and methods used in clinical laboratories have been applied to characterize a new Standard Reference Material (SRM), SRM 1955, "Homocysteine and Folate in Human Serum," containing low, medium, and high levels of tHCY and 5MT. Additionally, FA, 5-formyltetrahydrofolic acid (5FT), vitamin B12, and total folate values are provided. Use of the new SRM should improve clinical measurements and will permit traceability to internationally recognized certified reference materials, as described by European Directive 98/79/EC on in vitro diagnostic medical devices.     

Certified reference material for the determination of perfluorooctane sulfonate in acrylonitrile-butadiene-styrene resin (NMIJ CRM 8155-a)

A certified reference material (CRM) for the determination of perfluorooctane sulfonate (PFOS) in acrylonitrile-butadiene-styrene (ABS) resin (NMIJ CRM 8155-a) has been issued by the National Metrology Institute of Japan (NMIJ). The bulk material was prepared by mixing commercial ABS resin powder and potassium PFOS and cut into square plates (20 × 20 mm, 2 mm thick) as the CRM. Analytical processes combined with isotope-dilution mass spectrometry and liquid chromatography/mass spectrometry were optimised and applied for characterisation. One of the approaches adopted by NMIJ for certification is that results from two or more primary methods of measurement should be used; thus, two optimised isotope-dilution mass spectrometric methods (Methods 1 and 2 with reprecipitation and with reprecipitation/solid phase extraction, respectively, were validated mutually and employed) were used to determine the certified value. Homogeneity and stability of the square plates were evaluated and their uncertainty contributions (as relative standard uncertainties) were 1.43% for inhomogeneity and 6.96% for approximately two years’ instability. The certified mass fraction of linear PFOS (heptadecafluoro-1-octanesulfonic acid) in the CRM with expanded uncertainty (coverage factor k = 2, approximately 95% confidence interval) was (33.1 ± 5.0) mg kg^?1 as free acid of PFOS.     

BAM‐L002—a new type of certified reference material for length calibration and testing of lateral resolution in the nanometre range

A new type of test sample for the determination of lateral resolution in surface analysis is presented. The certified reference material BAM‐L002 ‘Nanoscale strip pattern for length calibration and testing of lateral resolution’ is an embedded cross‐section of epitaxially grown layers of Al_xGa_1?xAs and In_xGa_1?xAs on GaAs substrate. The surface of the sample provides a flat pattern with strip widths of 0.4–500 nm. The combination of gratings, isolated narrow strips and sharp edges of wide strips offers improved possibilities for the calibration of a length scale, the determination of lateral resolution and the optimization of instrument settings. The feasibility of the reference material for an analysis of lateral resolution is demonstrated for SIMS. Copyright © 2004 John Wiley & Sons, Ltd.     

Preparation and homogeneity study of a mussel candidate reference material for certification of organotin compounds

Organotin compounds are currently determined in various environmental matrices (in particular water, sediment and shellfish) to form the basis of control measures for the levels of contamination, as required in some EC Directives. Accurate measurements are a prerequisite for the enforcement of this legislation, which implies that good quality control of determinations should be ensured. One of the tools for achieving accuracy is to use certified reference materials (CRMs). With regard to tin species, however, CRMs are rather scarce and mainly concern sediment and fish matrices certified for their butyltin content. The present study deals with the preparation of a mussel candidate reference material and the verification of its homogeneity prior to the certification of the contents of butyl- and phenyl-tin compounds. 100kg of mussels (Mytilus edulis) were collected, carefully washed with fresh water in order to eliminate matrix salts and immediately frozen by immersion in liquid nitrogen. The mussels were shelled (in the frozen state) and the edible part was stored in thermally sealed polyethylene bags which were stored at –25 °C. The frozen material was ground in a Teflon-coated grinding mill, spread on sterilized flat trays and freeze-dried. The freeze-dried material was then ground for 15 days in a zirconia ball mill and sieved on a titanium sieve to separate the fibrous part. Successively, the material was mixed for 15 days under argon atmosphere in a special polyethylene-lined mixing drum and bottled in brown Pyrex-glass bottles. 21 bottles were selected during the course of the bottling procedure to verify the within- and between-bottle homogeneity of the overall batch. The within-bottle homogeneity was verified by determining the organotin (butyl- and phenyltins) content for subsamples of 500 mg in ten replicates from one bottle, whereas the between-bottle homogeneity was controlled by one organotin measurement from each of 20 bottles. The analyses were performed by GC-MS. The results showed that the homogeneity of the material makes it suitable as a candidate reference material.     

Human urine certified reference material CZ 6009: creatinine,styrene metabolites (mandelic acid and phenylglyoxylic acid)

The reference material was prepared by freeze-drying pooled urine samples obtained from healthy persons occupationally exposed to styrene. The concentrations of mandelic acid (MA), phenylglyoxylic acid (PGA), and hippuric acid (HA) in urine were determined by three modes of high-performance liquid chromatography (HPLC). For isochronous stability testing the urinary mandelic acid and phenylglyoxylic acid concentrations were followed over a 24-month period for a preliminary batch by use of HPLC. No changes of the concentration values were found. The creatinine concentration was stable for more than five years. Standard Reference Material NIST 914a Creatinine was used for traceability purposes for creatinine. Pure chemicals MA and PGA were used for traceability purposes. Control material ClinChek-Urine Control (Recipe) was analyzed simultaneously. The mean values of MA and PGA compare well with the means and fall within the control range of control samples. Results from homogeneity, stability, and traceability testing were evaluated using the statistical program ANOVA. The certified values and their uncertainties were evaluated from the results of interlaboratory comparisons, and homogeneity and stability tests. The values are unweighed arithmetical averages of accepted results and their uncertainties are combined uncertainties (coverage factor=1).Abbreviations MA Mandelic acid - HA Hippuric acid - PGA Phenylglyoxylic acid - 3-HBA 3-Hydroxybenzoic acid - ANOVA Analysis of variance - CV Coefficient of variance - NIST National Institute of Standards and Technology - HPLC High-performance liquid chromatography     

Preparation and analysis of a reference material for the measurement of oxygen in copper

The preparation and analysis of the oxygen mass fraction of three pure copper reference materials (BAM-379/1, BAM-379/2, BAM-379/3) intended for the calibration of spark emission spectrometry are described here. Data of homogeneity testing and round robin certification in collaboration with 12 independent laboratories from metalworking industry and research are reported. Problems with the establishment of traceability in this special case are discussed. Received: 20 July 2001 Accepted: 13 October 2001     

Characterization and traceability of two generations of standard reference material for the measurement of vitamin K1(phylloquinone) at endogenous concentrations in human plasma and serum

Vitamin K is an essential micronutrient required for blood coagulation, regulation of vascular calcification and bone mineralization. Plasma and serum measurements of vitamin K₁(phylloquinone, K₁) made using high-performance liquid chromatography with fluorescence detection, or tandem mass spectrometry are used clinically and in population studies to assess vitamin K status. Standard reference materials provide a validation tool for laboratories, helping assure clinical diagnosis and the comparability of data from different populations. We manufactured two K₁ standard reference materials, in 2009 (KEQAS SRM-001) and in 2019 (KEQAS SRM-002). The target concentrations of K₁ were assigned to each SRM using the All Laboratory Trimmed Mean of results reported by selected laboratories enrolled in the Vitamin K External Quality Assurance Scheme (KEQAS). The assigned concentrations of K₁ for KEQAS SRM-001 and SRM-002 were 0.25 and 0.36 μg/L respectively. In 2019 KEQAS SRM-001 was re-analysed simultaneously with KEQAS SRM-002 to provide traceability between the two standards, therefore aiding comparability of analysis performed using these materials. Both standards were stored as aliquots at −80°C in the dark; annual re-analysis of the materials indicated that K₁ is stable for at least 12 years in these conditions.     

Chromium speciation studies in human plasma and stability studies of Cr(III) and Cr(VI) species in a candidate water reference material

The aim of the research on Cr-speciation in plasma is to study the distribution of Cr over the plasma proteins. Cr is known to be mainly bound to transferrin and albumin. Therefore, a suitable separation procedure was developed for the two proteins. It consisted of a combination of FPLC cation and anion exchange, ensuring a complete resolution of both proteins and a total recovery of the Cr.In order to investigate the environmental impact of Cr(III) and Cr(VI) discharges, an aqueous reference material is needed to assess the quality of measurement between different laboratories. A pilot study was initiated to investigate the stability of a Cr(III) and Cr(VI) mixture in a bicarbonate/ carbonate buffer. Different parameters liable to influence the stability of the solutions have been investigated.     

Development of saw palmetto (Serenoa repens) fruit and extract standard reference materials

As part of a collaboration with the National Institutes of Health’s Office of Dietary Supplements and the Food and Drug Administration’s Center for Drug Evaluation and Research, the National Institute of Standards and Technology has developed two standard reference materials (SRMs) representing different forms of saw palmetto (Serenoa repens), SRM 3250 Serenoa repens fruit and SRM 3251 Serenoa repens extract. Both of these SRMs have been characterized for their fatty acid and phytosterol content. The fatty acid concentration values are based on results from gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC/MS) analysis while the sterol concentration values are based on results from GC-FID and liquid chromatography with mass spectrometry analysis. In addition, SRM 3250 has been characterized for lead content, and SRM 3251 has been characterized for the content of β-carotene and tocopherols. SRM 3250 (fruit) has certified concentration values for three phytosterols, 14 fatty acids as triglycerides, and lead along with reference concentration values for four fatty acids as triglycerides and 16 free fatty acids. SRM 3251 (extract) has certified concentration values for three phytosterols, 17 fatty acids as triglycerides, β-carotene, and γ-tocopherol along with reference concentration values for three fatty acids as triglycerides, 17 fatty acids as free fatty acids, β-carotene isomers, and δ-tocopherol and information values for two phytosterols. These SRMs will complement other reference materials currently available with concentrations for similar analytes and are part of a series of SRMs being developed for dietary supplements. Contribution of the US Government; not subject to copyright     

Preparation of a reference mussel tissue material for polycyclic aromatic hydrocarbons and trace metals determination

Due to high cost of certified reference materials (CRMs), reference materials (RMs) are preferred to check the method performance in environmental analysis. In this work, a laboratory reference material (LRM) was prepared and characterised to carry out the quality control in monitoring analysis of eight polycyclic aromatic hydrocarbons (PAHs) and nine trace metals in mussel tissue. Mussels were collected in a naturally polluted area. Before the reference material was bottled, the mussel tissue was stabilised by freeze-drying, ground and sieved. For the material characterisation, several statistical tests were applied to check the homogeneity of the analytes in the tissue, and a stability test was performed to study the effect of the storage temperature in the analyte concentration. Other characteristics such as specific density, moisture and lipid contents as well as particle size distribution of the material were determined. Although the LRM had a homogeneous distribution for all PAHs and almost all metals, the stability study showed different results at both storage temperatures studied. For both PAHs and trace metals, the material was suitable to assure the quality control of the analysis.     

A new Antarctic certified reference material for trace elements: Adamussium colbecki

The certification of a new reference material for trace elements based on the Antarctic bivalve Adamussium colbecki is reported. This certified reference material (CRM), labelled IRMM 813, was produced in the frame of the Italian National Program for Research in Antarctica (Programma Nazionale di Ricerca in Antartide, PNRA). About 40 kg of the scallop were collected at Terra Nova Bay (Ross Sea). The raw material was freeze-dried, jet-milled and homogenized so as to make it suitable for certification. The elements selected for the certification project were As, Cd, Cu, Cr, Fe, Mn, Ni and Zn. Homogeneity and short- and long-term stability were preliminarily investigated so as to assess the suitability of the freeze-dried mass as a candidate CRM. The candidate material was found to be fit for purpose, thus allowing the following phases of the certification project to be undertaken, in the first place the selection of expert laboratories for the accomplishment of the certification campaign. Eighteen laboratories from twelve countries accepted to participate in the certification project which thus could be successfully completed.     

Certified reference materials (CRMs 398 and 399) for the quality control of major element determination in freshwater

Analyses of freshwater are routinely performed by a number of organisations to monitor the levels of major elements. In order to improve and control the quality of such determinations, the Community Bureau of Reference (BCR) has organised a certification campaign to produce two reference materials (CRM 398, low element content and CRM 399, high element content) certified for their contents of Al, Ca, Cl, Fe, Mg, Mn, K, Na, P and S. These materials were carefully prepared (addition of the elements mentioned in the form of ammonium salts or nitrates to silica free deionised water) and their homogeneity and long term stability were verified. This paper presents the certification work performed.     

Certified sediment reference materials for trace element analysis from the National Metrology Institute of Japan (NMIJ)

Two types of sediment reference material (NMIJ 7302-a and 7303-a) for trace elements analysis have been prepared and certified by the National Metrology Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The original materials were collected from a bay near industrial activity in Kyushu (NMIJ CRM 7302-a; marine sediment) and from Lake Biwa (NMIJ CRM 7303-a; lake sediment). The sediment materials were air-dried, sieved, homogenized, packaged in 1000 glass bottles (60 g each), and radiation sterilized. Certification of these CRM for trace elements was conducted by NMIJ, where each element was determined by at least two independent analytical techniques. Isotope-dilution inductively coupled plasma mass spectrometry (ICP–MS) was applied for certification of all the elements except mono-nuclide elements such as As and Co. Other techniques such as ICP–MS with quadrupole mass spectrometry and sector-field mass spectrometry, inductively coupled plasma atomic emission spectrometry (ICP–AES), and atomic absorption spectrometry (AAS), were also used. Certified values have been provided for 14 elements (Sb, As, Cd, Cr, Co, Cu, Pb, Hg, Mo, Ni, Se, Ag, Sn, and Zn) in both CRM.     

A CBNM isotopic reference material set for testing linearity of isotope mass spectrometers (CBNM IRM 072/1-15)

Summary Any mass spectrometric measurement system has inherent inaccuracies caused by isotope fractionation in the ion source and non-linearity of the detector and or measurement system. A set of well known triple isotope mixtures is an excellent means to verify and correct non-linearity of the mass spectrometer detector and measurement system after the isotope fractionation has been corrected for. CBNM IRM 072/1-15 is a set of such mixtures. Its preparation and characterization is described. It is available for interested users.

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CBNM Isotopen-Referenzmaterial zur Prüfung der Linearität von Isotopen-Massenspektrometern (CBNM IRM 072/1-15)