NIES certified reference materials for arsenic speciation

 The National Institute for Environmental Studies (NIES) recently prepared two candidate certified reference materials (CRMs) for arsenicals to meet the growing demand for the quality assurance of arsenic speciation analysis. The NIES candidate CRM No. 14 Brown Alga was prepared from Hijiki seaweed for the certification of inorganic arsenic content, and No. 15 Scallop was prepared from adductor muscle of scallop for the certification of arsenobetaine content. The preparation of the candidate CRMs is briefly described. Cooperative analyses for total arsenic content of the candidate CRMs have been underway. The preliminary speciation analysis at NIES revealed difficulty in establishing suitable conditions for extracting arsenic species from the materials. Chromatograms of arsenic species by a high performance liquid chromatography-inductively coupled plasma mass spectrometric detection system are presented to provide information about arsenic species present in these candidate CRMs.     

Sol-gel zirconia coating capillary microextraction on-line hyphenated with inductively coupled plasma mass spectrometry for the determination of Cr, Cu, Cd and Pb in biological samples

A sol-gel zirconia coating was developed for the preconcentration/separation of trace Cr, Cu, Cd and Pb by capillary microextraction, and the adsorbed analytes were on-line eluted for detection using inductively coupled plasma mass spectrometry (ICP-MS). By immobilizing sol-gel zirconia on the inner surface of a fused-silica capillary, the sol-gel zirconia coating was simply prepared. Its adsorption properties, stability and the factors affecting the adsorption behaviors of Cr, Cu, Cd and Pb were investigated in detail. In the pH range from 7.8 to 10, the zirconia-coated capillary (35 cm x 0.15 mm) is selective towards Cr, Cu, Cd and Pb, and the analyzed ions could be desorbed quantitatively with 0.2 mL of 0.5 mol/L HNO(3) at a rate of 0.2 mL/min. With a consumption of 1.25 mL sample solution, an enrichment factor of 6.25, and detection limits (3sigma) of 9.9 pg/mL Cr, 17.9 pg/mL Cu, 4.5 pg/mL Cd and 3.7 pg/mL Pb were obtained. The precisions for nine replicate measurements of 1 ng/mL Cr, Cu, Cd and Pb were 4.9% Cr, 2.2% Cu, 2.0% Cd and 3.2% Pb (RSD), respectively. The proposed procedure has been applied to the determination of Cr, Cu, Cd and Pb in human urine, which was subjected to microwave-assisted digestion prior to analysis, and the recoveries for these elements were 89.2-101.8%. In order to validate the developed procedure, a NIES No.10-a Rice Flour-Unpolished certified reference material and a BCR No. 184 Bovine Muscle certified reference material were analyzed, and the results are in good agreement with the certified values.     

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 organic arsenic compounds in bivalves

Water-soluble arsenic compounds were extracted with methanol/water (1:1, v/v) from various species of bivalves and also from certified reference materials (NIES No. 6, mussel tissue, and NBS 1566, oyster tissue). The extracts were analyzed with a high-performance liquid chromatograph combined with an inductively coupled argon plasma mass spectrometer serving as an arsenic-specific detector. A certified reference material (NIES No. 6) was used to check the reproducibility of the analysis. The relative standard deviations (RSDs) of the peak area of major arsenic compounds among repeated measurements (n = 6) on the same extrct were less than 3.3%, indicating good reproducibility of the technique. The RSDs of some peaks among measurements of independent extracts, on the other hand, were more than 10%, possibly reflecting the heterogeneity of the sample in terms of the chemical species under the present experimental conditions. In many of the samples analyzed in the present study, two arsenic-containing ribofuranosides were detected in addition to arsenobetaine. A compound bearing a glycerophosphoryl glycerol moiety was dominant in such cases. Interestingly, a bivalve living in an estuary (Corbicula japonica) did not contain a detectable amount of arsenobetaine though it had arsenic-containing ribofuranosides. The distribution of arsenic species in the various parts of a clam (Meretrix lusoria) and a mussel (Mytilus coruscum) was also analyzed.     

New human hair certified reference material for methylmercury and trace elements

 A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1,000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given. Received: 8 February 1996/Accepted: 4 April 1996     

New human hair certified reference material for methylmercury and trace elements

A new human hair certified reference material (NIES CRM No. 13) for mercury speciation and trace element analysis was prepared at the National Institute for Environmental Studies (NIES), Environmental Agency of Japan. Scalp hair from Japanese males, which is identical with the original material for the previous human hair CRM (NIES CRM No. 5), was used. Special attention was paid to reduce contamination from a grinding vessel during the preparation procedure. A newly-prepared ceramic/Teflon disc mill was used for cryogenic grinding of the hair. 1, 000 bottles (3 g each) were produced after sieving and blending of the hair powder. Certified values for total mercury and methylmercury, as well as other trace elements of toxicological and nutritional significance (antimony, cadmium, copper, lead, selenium, and zinc), were determined based on analyses from extensive collaborations. Reference values for 12 elements (aluminium, arsenic, barium, calcium, cobalt, iron, magnesium, manganese, silver, sodium, sulfur and vanadium) were also given.     

Elemental content of Vietnamese rice. Part 1. Sampling, analysis and comparison with previous studies

Various rice samples were collected in Vietnam from the Red River region, and some other parts of the country as well as from Yanco, NSW, Australia. The rice samples were analysed for 14 elements (P, K, Mg, Ca, Mn, Zn, Fe, Cu, Al, Na, Ni, As, Mo, and Cd) by ICP-AES, ICP-MS and FAAS. The analytical procedures were carefully controlled and validated using the rice flour certified material (NIES No 10). In general, the results showed that Vietnamese rice has elemental concentration ranges similar to those of the Australian and other overseas rice. However, analyses for some elements are characteristic of some Vietnamese and Australian rice samples. Thus, Vietnamese rice shows somewhat higher levels of P, K and Mg than rice samples from other countries; Mn could be a marker for the Australian rice grown in the Yanco region, and the analysed Australian samples were also very low in Cd (< 0.003 mg kg-1). An unusual distribution of Ni, present in higher concentrations in the white rice samples than in the brown ones, was observed for some Vietnamese rice samples.     

Certification of the cadmium content in certified reference materials for Cd rice flour

The materials used to prepare the certified reference materials (CRMs) for Cd rice flour described here were taken from Cd-contaminated rice samples, round-grained and non-sticky rice grown in different provinces throughout China. The Cd rice materials were first blown to remove dust and husk, and then were successively ground, sieved, dried and mixed to form homogeneous rice flour. The Cd rice flour was packed in glass bottles, each bottle containing 40 g. All bottled CRMs were subjected to 60Co radiation (2.5 megarads) for long-term preservation. Atomic absorption spectrometry was used to determine the homogeneity of the cadmium content in each material. The certification of the cadmium content for the three CRMs was performed using isotope dilution mass spectrometry.     

Instrumental neutron activation analysis for quality assurance of a hair reference material for mercury speciation

Instrumental neutron activation analysis (INAA) has been employed in the investigation of mass balance for mercury species analysis in the analytical process. A new human hair reference material (IAEA-085) was analyzed for methylmercury using a solid/liquid extraction procedure, with samples of extracts, residues, and untreated samples being analyzed by INAA. The certified reference material NIES CRM No. 13, human hair, was analyzed in parallel. From the results obtained through the mass balance studies, it was found that the extraction procedure was quantitatively complete, and that there was no difference between the mass balance of Hg and the total Hg in the untreated materials.     

Development of a highly precise ID-ICP-SFMS method for analysis of low concentrations of lead in rice flour reference materials

Microwave digestion and isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-SFMS) has been applied to the determination of Pb in rice flour. In order to achieve highly precise determination of low concentrations of Pb, the digestion blank for Pb was reduced to 0.21 ng g⁻¹ after optimization of the digestion conditions, in which 20 mL analysis solution was obtained after digestion of 0.5 g rice flour. The observed value of Pb in a non-fat milk powder certified reference material (CRM), NIST SRM 1549, was 16.8 ± 0.8 ng g⁻¹ (mean ± expanded uncertainty, k = 2; n = 5), which agreed with the certified value of 19 ± 3 ng g⁻¹ and indicated the effectiveness of the method. Analytical results for Pb in three brown rice flour CRMs, NIST SRM 1568a, NIES CRM 10-a, and NIES CRM 10-b, were 7.32 ± 0.24 ng g⁻¹ (n = 5), 1010 ± 10 ng g⁻¹ (n = 5), and 1250 ± 20 ng g⁻¹ (n = 5), respectively. The concentration of Pb in a candidate white rice flour reference material (RM) sample prepared by the National Metrology Institute of Japan (NMIJ) was observed to be 4.36 ± 0.28 ng g⁻¹ (n = 10 bottles). Figure Digestion blank of Pb was carefully reduced to approximately 0.2 ng g^-1 which permitted the highly precise determination of Pb at low ng g^-1 level in foodstuff samples by ID-SFMS     

Homogeneity studies in reference materials with Zeeman solid sampling GFAAS

Summary The homogeneity of lead and cadmium in reference materials was investigated by solid sampling GFAAS. The following materials were comparatively analyzed: Standard reference materials from NBS, Washington 1567 Wheat flour, 1568 Rice flour and 1577a Bovine liver, certified reference materials from BCR, Brussels, No 63 Milk powder, No 184 Bovine muscle, No 185 Bovine liver, No 186 Pig kidney, No 189 Wholemeal flour, No 191 Brown bread and a whole fish (dab) homogenate from the environmental specimen bank in the FRG. The results are remarkably different for the investigated materials.

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Homogenit?tsstudien in Referenzmaterialen mit Zeeman-Feststoff-GFAAS

     

Substoichiometric Isotope Dilution Analysis for the Determination of Iron in Biological Materials and Comparison with Substoichiometric Isotope Dilution Mass Spectrometry

Substoichiometric isotope dilution analysis for the determination of trace iron has been studied by using synergistic extraction of iron(III) with a substoichiometric amount of 4-isopropyltropolone (Hipt) in the presence of an excess of 3,5-dichlorophenol (DCP) in heptane. Optimum conditions for the substoichiometric extraction of iron(III) in g to sub-g levels were examined and the high selectivity for iron(III) toward various metal ions encountered in the analysis of biological materials was confirmed. The present method was applied to a biological reference material (NIES, CRM No.9, sargasso) without any pre-separation and was successfully evaluated. Furthermore, substoichiometric stable isotope dilution mass spectrometry using the present extraction method was also used with the above sample. Applicability and practicability was compared for both substoichiometric methods.     

New reference material for analysis of elements in glutinous rice produced at the National Institute of Metrology (Thailand)

Reference materials play an important role for evaluating the accuracy of analytical results, and are essential parts of good laboratory practice. They represent a key tool for quality control of chemical analyses. In Thailand, the demand of food and environmental reference materials is constantly increasing, and the National Institute of Metrology (NIMT, Thailand) is responding to the urgent needs for affordable materials, which require collaborative efforts at the national level. This paper describes the preparation of a new glutinous rice reference material, along with homogeneity and stability studies and the analytical work carried out for the certification of the contents of inorganic elements. The incurred material was collected from an actual rice paddy field. Material preparation along with homogeneity and stability testing were carried out at the Environmental Research Training Centre (ERTC). The homogeneity study was designed to have three experimental conditions; (A) 10 bottles of candidate materials being analyzed each with 2 replicates, (B) 20 bottles with 2 replicates, (C) 10 bottles with 7 replicates, in order to study the suitable treatments for homogeneity testing in the reference material production. It was shown that a minimum number of 10 bottles with duplicate analyses are enough to demonstrate the homogeneity of candidate reference material. Certification of a candidate reference material in a single laboratory using reference method was confirmed with an interlaboratory comparison participated by a certain number of well recognized testing laboratories in Thailand. Further elaborative results will be discussed.     

Comparison of standard materials for the establishment of calibration curves in solid sampling graphite furnace atomic absorption spectrometry. Direct determination of copper in powdered biological samples

Summary The selection of standard materials for the establishment of calibration curves is one of the most important problems in the direct analysis of biological samples by GFAAS. Three kinds of standard materials, NBS tomato leaves, coprecipitates with magnesium oxinate and Ni/DMG/PAN were investigated. It was found that it is possible to use both the NBS-SRM and the synthetic reference material prepared by coprecipitation with magnesium oxinate as standard materials for the direct determination of copper in several biological samples issued from NBS and NIES. However, too low results are obtained when the synthetic reference material prepared by coprecipitation with Ni/DMG/PAN is used. In order to clarify this, the effects of nickel and magnesium were examined and the role of magnesium was discussed.     

Homogeneity studies in a variety of reference materials using solid sampling Zeeman graphite furnace AAS

Summary For evaluation and homogeneity estimation in several plant reference and candidate reference materials from different sources, including two 2nd generation environmental specimen bank (ESB) candidate reference materials, prepared by cryogenic milling of fresh spruce shoots, solid sampling graphite furnace AAS (SSGFAAS) was used. The results obtained for the elements cadmium, copper, lead and nickel demonstrate good homogeneity even at intakes from 0.1 to 2 mg for the ESB materials in comparison to classical NIST and NIES certified reference materials of proven homogeneity and reliability.     

An enrichment method of molybdenum on a cellulose nitrate resin for the determination by electrothermal atomic absorption spectrometry coupled with the resin suspension injection.

Cellulose derivative resin (CDR) suspensions containing resin particles of cellulose nitrate (CDR(CN)), cellulose acetate (CDR(CA)), or cellulose triacetate (CDR(CTA)) were prepared as the sorbent for resin suspension injection (RSI) electrothermal atomic absorption spectrometry (ETAAS), in which fine resin particles holding a desired trace element were directly injected into the graphite tube as the suspension. To compare the sorption ability, the distribution ratios of the Mo(VI)-phenylfluorone complex were measured between the aqueous phase and the sorbents, including the CDRs mentioned above and the finely divided anion exchange resin (AR). The results showed that the sorption ability decreases in the following order: CDR(CN) > or = AR > CDR(CA) > or = CDR(CTA). It was concluded that CDR(CN) was able to extract more than 98% of Mo(VI), and was suitable for RSI-ETAAS as well as AR. CDR(CN) was used for the determination of Mo in NIES certified reference materials, No. 10 Rice flour-unpolished; the results showed fairly good agreements between the analytical values and the certified values.     

Simplified sample preparation for GC speciation analysis of organotin in marine biomaterials

Two simple sample preparation methods for the speciation analysis of triphenyltin and butyltin compounds in marine biotissues, using tetramethylammonium hydroxide (TMAH) solubilization and enzymic hydrolysis, have been developed and compared with conventional acid digestion. Derivatization was carried out in situ using sodium tetraethylborate (NaBEt₄) without prior separation of the analytes from the tissue matrix. Separation and detection was performed using capillary gas chromatography (GC) coupled to microwave-induced plasma atomic emission spectrometry (MIP AE) allowing detection limits of 2 ng g^?1 (as tin) to be reached. The accuracy of the presented methods was demonstrated by the analysis of a fish reference material (NIES No. 11). the necessity for sample clean-up is discussed and examples of the analysis of mussel tissue are shown.     

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.     

The search for kinetic reference materials for adiabatic and differential scanning calorimetry

No reference materials are currently available to study thermoanalytical kinetic methods, apparatus, or software. The ASTM International Committee E27 on Hazard Potential of Chemicals seeks to identify possible calorimetric reference materials for evaluating kinetic parameters, including activation energy (E), log pre-exponential factor (log Z), and reaction orders (m and n), as well as reaction enthalpy (H). Six candidate materials are examined including di-tertiary-butyl peroxide (DTBP), trityl azide, azobenzene, azobisisobutyronitrile (ABIN), cumene hydroperoxide (CHP), and phenytetrazolthiol. No single material appears to meet all needs. The merits and applicability of each candidate are discussed and recommended kinetic reference values are presented.     

Assessment of total arsenic and arsenic species stability in alga samples and their aqueous extracts

In order to achieve reliable information on speciation analysis, it is necessary to assess previously the species stability in the sample to analyse. Furthermore, in those cases where the sample treatment for species extraction is time-consuming, an assessment of the species integrity in the extracts is of paramount importance. Thus, the present paper reports total arsenic and arsenic species stability in alga samples (Sargassum fulvellum and Hizikia fusiformis), as well as in their aqueous extracts, which were stored in amber glass and polystyrene containers at different temperatures. Total arsenic determination was carried out by inductively coupled plasma atomic emission spectroscopy (ICP-AES), after sample acid digestion in a microwave oven, while arsenic speciation was conducted by anion exchange high performance liquid chromatography on-line coupled to ICP-AES, with and without sample introduction by hydride generation (HPLC-ICP-AES and HPLC-HG-ICP-AES), after aqueous microwave-assisted extraction. The results obtained for solid alga samples showed that total arsenic (for Hijiki alga) and arsenic species present (As(V) for Hijiki and NIES No. 9 Sargasso) are stable for at least 12 months when samples are stored in polystyrene containers at +20 degrees C. On the other hand, a different behaviour was observed in the stability of total arsenic and As(V) species in aqueous extracts for both samples, being the best storage conditions for Sargasso extracts a temperature of -18 degrees C and polystyrene containers, under which they are stable for at least 15 days, while Hijiki extracts must be stored in polystyrene containers at +4 degrees C in order to ensure the stability for 10 days.