Certified Reference Material

In this present work the distribution of heavy metals in sea water and sediments of the Salerno Gulf is measured. The elements determined were Cu, Pb, Cd, Zn and Hg, employing, as instrumental techniques, either differential pulse anodic stripping voltammetry (DPASV) or graphite furnace atomic absorption spectroscopy (GFAAS). A comparison of the results of the two analytical techniques is also made. Mercury determination was carried out employing the cold vapour atomic absorption spectroscopy (CVAAS) technique, with SnCl 2 as the reducing agent. The sample digestion was performed by a new procedure using concentrated suprapure H 2 SO 4-K 2 Cr 2 O 7 mixture. The accuracy and precision of the analytical procedure were evaluated employing Sea Water BCR-CRM 403 and Estuarine Sediment BCR-CRM 277 as reference materials. Accuracy, expressed as relative error e and precision, expressed as relative standard deviation s r , were in order of 2 to 5%. For both matrices, the detection limits, for all the elements, were in the range µg g −1 to ng g −1 .

There is accumulating evidence that the metabolism of several trace elements is altered in diabetes mellitus and that these nutrients might have specific roles in the pathogenesis and progress of this disease. The aim of present study was to compare the level of essential ...

Leaching experiments, a mineralogical survey and larger samples are preferred when arsenic is present as discrete mineral phases. Abstract Availability, mobility, (phyto)toxicity and potential risk of contaminants is strongly affected by the manner of appearance of elements, the so-called speciation. Operational fractionation methods like sequential extractions have been applied for a long time to determine the solid phase speciation of heavy metals since direct determination of specific chemical compounds can not always be easily achieved. The three-step sequential extraction scheme recommended by the BCR and two extraction schemes based on the phosphorus-like protocol proposed by Manful (1992, Occurrence and Ecochemical Behaviours of Arsenic in a Goldsmelter Impacted Area in Ghana, PhD dissertation, at the RUG) were applied to four standard reference materials (SRM) and to a batch of samples from industrially contaminated sites, heavily contaminated with arsenic and heavy metals. The SRM 2710 (Montana soil) was found to be the most useful reference material for metal (Mn, Cu, Zn, As, Cd and Pb) fractionation using the BCR sequential extraction procedure. Two sequential extraction schemes were developed and compared for arsenic with the aim to establish a better fractionation and recovery rate than the BCR-scheme for this element in the SRM samples. The major part of arsenic was released from the heavily contaminated samples after NaOH-extraction. Inferior extraction variability and recovery in the heavily contaminated samples compared to SRMs could be mainly contributed to subsample heterogeneity. #

A simple method for the separation and determination of inorganic arsenic (iAs) species in natural and drinking water was developed. Procedures for sample preparation, separation of As(III) and As(V) species and preconcentration of the total iAs on fixed bed columns were defined. Two resins, a strong base anion exchange (SBAE) resin and a hybrid (HY) resin were utilized. The inductively-coupled plasma-mass spectrometry method was applied as the analytical method for the determination of the arsenic concentration in water. The governing factors for the ion exchange/sorption of arsenic on resins in a batch and a fixed bed flow system were analyzed and compared. Acidity of the water, which plays an important role in the control of the ionic or molecular forms of arsenic species, was beneficial for the separation; by adjusting the pH values to less than 8.00, the SBAE resin separated As(V) from As(III) in water by retaining As(V) and allowing As(III) to pass through. The sorption activity of the hydrated iron oxide particles integrated into the HY resin was beneficial for bonding of all iAs species over a wide range of pH values from 5.00 to 11.00. The resin capacities were calculated according to the breakthrough points in a fixed bed flow system. At pH 7.50, the SBAE resin bound more than 370 g g −1 of As(V) while the HY resin bound more than 4150 g g −1 of As(III) and more than 3500 g g −1 of As(V). The high capacities and selectivity of the resins were considered as advantageous for the development and application of two procedures, one for the separation and determination of As(III) (with SBAE) and the other for the preconcentration and determination of the total arsenic (with HY resin). Methods were established through basic analytical procedures (with external standards, certified reference materials and the standard addition method) and by the parallel analysis of some samples using the atomic absorption spectrometry-hydride generation technique. The analytical properties of both procedures were similar: the limit of detection was 0.24 g L −1 , the limit of quantification was 0.80 g L −1 and the relative standard deviations for samples with a content of arsenic from 10.00 to 300.0 g L −1 ranged from 1.1 to 5.8%. The interference effects of anions commonly found in water and some organic species which can be present in water were found to be negligible. Verification with certified reference materials proved that the experimental concentrations found for model solutions and real samples were in agreement with the certified values.

Different methods for the determination of several metals in soils by flame atomic absorption spectrometry (FAAS) were investigated. Different procedures for total dissolution of soil: I -HF+HClO 4 , H 3 BO 3 , HCl digestion (conventional heating), II -HF+HClO 4 , H 3 BO 3 digestion followed by fusion with LiBO 2 (conventional heating) and III -HF+HCl+HNO 3 , H 3 BO 3 digestion (microwave heating), as well as a leaching procedure with HNO 3 +HClO 4 , HCl were tested and compared. For quality assessment, the certified reference material S-1 soil was used. For most of the investigated metals, the best accuracy and precision were achieved when the procedure I or III were used. The developed procedure was applied to the analysis of soil samples from crude oil refinery and dump of petroleum origin wastes regions.

A chelating resin, pyrocatechol violet (PV) immobilised on an Amberlite XAD-1180 support, was prepared and its use for the atomic absorption spectrometric determination of aluminium was investigated. The XAD-1180-PV resin was characterised by infrared spectrometry and thermal gravimetric analysis. The optimum pH value for quantitative sorption is 8-9, and desorption can be achieved by using 5.0-10.0 ml of 2 M HCl. The effects of diverse ions on the sorption and recovery of aluminium have been studied. The capacity of sorbent was 6.45 ± 0.59 mg g −1 Al XAD-1180-PV. Recoveries for aluminium from water samples were in the range 95-105%. The accuracy of procedure was confirmed by aluminium determination in certified reference materials. The method developed was applied with varying results to the analysis of natural water, haemodialysis fluids and microwave digested red wine samples from Tokat City.

Ž . Ž . The effects of tetrahydroborate 0.02᎐1% and iodide 0᎐3 M were investigated in determination of tellurium and selenium by hydride generation atomic fluorescence spectrometry. The effect of tetrahydroborate and iodide concentration were tested on the shape of calibration curves in concentration range of 1᎐1000 ng ml y1 analyte. Reductant deficiency resulted in a moderate sensitivity depression for tellurium but dramatically reduced the useful dynamic range down to 50 ng ml y1 . On the contrary, selenium calibration curves retained a linear character even under conditions generating strong sensitivity depression. Curvature and rollover of tellurium calibration curves has been addressed to a self-interference effect caused by the formation of finely dispersed elemental tellurium. Iodide ions were found to have beneficial or no negative effects in the hydrogen telluride generation. Addition of iodide on-line to the sample has been proved effective in the control of the self-interference effect and allows to work in Ž . Ž . Ž . mild reaction conditions. Moreover, it allows a good control of Cu II interference and eliminates Ni II and Co II interferences. The method has been successfully applied to determination of tellurium in copper and lead ores certified reference materials. ᮊ

Beef and beef fat control composites (CC) were prepared for a large multi-year study of conjugated linoleic acid (CLA) and trans-vaccenic acid (TVA) in beef. Raw ground beef and beef suet were each frozen in liquid nitrogen, ground to a fine powder, dispensed into subsamples, and stored at − 60°C under nitrogen. The CCs, reference materials (beef/pork fat; meat homogenate), and standards prepared at two concentrations of CLA and TVA added to a total lipid extract of beef (differing by 0.27 g/100 g CLA and 1.2432 g/100 g TVA) were analyzed via alkaline saponification of lipids, derivatization to fatty acid methyl esters, and GC. CLA and TVA recoveries from the standards were 95-113% (CLA) and 103-106% (TVA). Fatty acids quantified in the reference materials were within the certified ranges. Relative standard deviations (n = 3 in each of 5 assay batches) were b 5% (TVA) and b 10% (CLA) for both CCs, at both laboratories.

Two procedures for the determination of Co in biological samples by graphite furnace atomic absorption spectrometry (GF AAS) were compared: solid sampling (SS) and alkaline treatment with tetramethylammonium hydroxide (TMAH) using two different instruments for the investigation: a conventional line-source (LS) atomic absorption spectrometer and a prototype high-resolution continuum source atomic absorption spectrometer. For the direct introduction of the solid samples, certified reference materials (CRM) were ground to a particle size V50 Am. Alkaline treatment was carried out by placing about 250 mg of the sample in polypropylene flasks, adding 2 mL of 25% m/v tetramethylammonium hydroxide and de-ionized water. Due to its unique capacity of providing a 3-D spectral plot, a high-resolution continuum source (HR-CS) graphite furnace atomic absorption spectrometry was used as a tool to evaluate potential spectral interferences, including background absorption for both sample introduction procedures, revealing that a continuous background preceded the atomic signal for pyrolysis temperatures lower than 700 8C. Molecular absorption bands with pronounced rotational fine structure appeared for atomization temperatures N1800 8C probably as a consequence of the formation of PO. After optimization had been carried out using high resolution continuum source atomic absorption spectrometry, the optimized conditions were adopted also for line-source atomic absorption spectrometry. Six biological certified reference materials were analyzed, with calibration against aqueous standards, resulting in agreement with the certified values (according to the t-test for a 95% confidence level) and in detection limits as low as 5 ng g À1 .

A new, simple and versatile cloud-point extraction (CPE) methodology has been developed for the separation and preconcentration of copper and nickel. The metals in the initial aqueous solution were complexed with 2-(2′-benzothiazolylazo)-5-(N, N-diethyl) ...

Direct injection high efficiency nebulizer (DIHEN)-inductively coupled plasma mass spectrometry (ICPMS) is investigated for analysis of petroleum samples dissolved in volatile organic solvents. To minimize solvent loading, the solution uptake rate is reduced to 10 mlymin, far less than the level (85 mlymin) commonly used for aqueous sample introduction with the DIHEN, and oxygen is added to the nebulizer gas flow and outer flow of the ICP. Factorial design is applied to investigate the effect of nebulizer tip position within the torch and the nebulizer and intermediate gas flow rates on the precision and the net signal intensity of the elements tested for multielemental analysis. Cluster analysis and principal component analysis are performed to distinguish the behavior of different isotopes, oxide species and doubly charged ions. The best operating conditions at a solution uptake rate of 10 mly min are: RF powers1500 W, nebulizer gas flow rates0.10-0.12 lymin, intermediate gas flow rates1.5 lymin and DIHEN tip positions3-4 mm below the top of the torch intermediate tube. Acceptable recoveries (100"10%) and good precision (less than 3% relative standard deviation) are obtained for trace elemental analysis in organic matrices (a certified gas oil sample and a custom-made certified reference material) using flow injection analysis. Because of high blank levels, detection limits are 1-3 orders of magnitude higher for organic sample introduction than those acquired for aqueous solutions. ᮊ

Reference materials (RMs) have emerged with the aim of improving analytical methods performance, in what regards to their validation, calibration, uncertainty, training and internal quality control, and of increasing the comparability of measurements between laboratories. Due to their unquestionable importance, but still low availability and high cost, the present work has determined the suitability of infant formula, powdered garlic, tea and infusion as quality control materials for phosphorus analysis. Phosphorous was determined using a spectrometric method. Homogeneity and stability were determined within and between samples according with ISO guidelines. The results show that quality control materials prepared under rigorous procedures are valuable tools in the food composition analysis.

Analytical data on element concentrations in plastics is an important prerequisite for the recycling of technical waste plastics. The chemical resistance and high additive contents of such materials place a high demand on analytical methods for quantifying elements in thermoplastics from electrotechnical applications. The applicability of three common independent analytical methods (EDXRF, AAS, ICP-AES) for the quantification of heavy metals in such technical waste plastics of varying composition was studied. Following specific sample pre-treatments, such as closed vessel microwave assisted digestion and wet ashing with H 2 SO 4 , three hazardous metals (Pb, Cd, Sb) were determined. Conditions were investigated to minimize matrix effects for all analytical techniques employed. The trueness for the quantification of Cd was checked by using the certified reference material VDA 001-004 (40-400 mg g − 1 Cd in polyethylene), and no significant differences to certified values were found. The best detection limits were found to be 2, 1.3 and 7.9 mg g − 1 for Cd, Pb and Sb, respectively. In technical waste polymers, Sb was detected to be in the range 1-7%, Cd in the range 80-12 000 mg g − 1 and Pb in the range 90-700 mg g − 1. The precision reached for the analysis of this complex material, is comparable for all methods, and can be expressed by a relative standard deviation smaller than 8%. Application of multivariate analysis of variances (MANOVA) showed no differences between the mean results, except for the ICP-AES analysis following wet ashing with H 2 SO 4 .

A procedure for the extraction of Cr(VI) from solid soil-like samples was presented in which the complexing properties of diethylenetriaminepentaacetic acid (DTPA) were exploited to extract insoluble compounds of Cr(VI). A concentration of DTPA in an ammonium sulphate/ammonium hydroxide buffer equal to 0.02 mol l −1 was chosen. The conditions of extraction of insoluble Cr(VI) from solid samples were optimised using soil certified reference material spiked with known concentration of insoluble Cr(VI) added as PbCrO 4 . The extracts were analysed by adsorptive stripping voltammetry. Validation of the proposed procedure of extraction was carried out by analysis of certified reference material (CRM) 545 and comparison of the results obtained using the proposed and other methods of extraction in the course of analysis of natural soil samples.

Focused ultrasonic-assisted extraction (FUSE) is a new and particular technique based on the cavitation effect. In this work, the focused ultrasound assisted extraction was studied and developed for the extraction of polycyclic aromatic hydrocarbons from marine sediments and mussel tissues. The variables influencing the extraction (amplitude of the ultrasound pulse, the extraction time and the solvent) were studied by a full factorial design and a central composite design. As a result, flat response surfaces were obtained and the most convenient conditions were 45% of ultrasound amplitude, 120 s of extraction time and 5 mL of acetone. Both accuracy and precision of the method were evaluated by means of two certified reference materials (marine sediment and mussel tissue) and the results were also compared to those obtained by microwave assisted extraction.

As from 25 November 2005 onwards, a list of ingredients with known allergenic potential has to be labeled according to Directive 2003/89/EC, including celery and products thereof. In order to provide appropriate detection methods a novel real-time polymerase chain reaction (PCR) system for the specific and sensitive detection of DNA from celery (Apium graveolens) was developed and validated. Specificity was confirmed by testing DNA derived from more than 50 food relevant organisms. Sensitivity was demonstrated on the basis of a calibration curve plotting the corresponding Ct-values against DNA amounts ranging from 1 to 1000 copies. Due to the lack of certified reference material the applicability of the method was assessed by analysis of sausages spiked with defined amounts of grounded celery seed. The limit of detection (LOD) examined exemplarily for emulsion-type sausages was 5-10 mg/kg. Analysis of celery-containing commercial products demonstrated the performance potential and limitations of the new real-time PCR system.

A comprehensive thermal conductivity (λ) database of three dry standard sands (Ottawa C-109, Ottawa C-190, and Toyoura) was developed using a transient line heat source technique. The database contains λ data representing a variety of soil compactions and temperatures (T) ranging from 25 • C to 70 • C. The tested standard sands, due to their repeatable physical characteristics, can be used as reference materials for validation of thermal probes applied to similar dry granular materials. The measured data show an increasing trend of thermal conductivity at dryness (λ dry) against T in spite of declining quartz λ with T. The air content (porosity) controls the λ of dry sands by acting as a very effective thermal insulator around solid soil particles. As a result, a diminutive increase of λ dry with T is driven by increasing λ of air. The experimental λ data of dry sands were exceptionally well predicted by de Vries and Woodside-Messmer models, and also by a thermal conductance model, a product of λ of solids and the thermal conductance factor.

As part of the United States Department of Agriculture's (USDA) National Food and Nutrient Analysis Program (NFNAP), food composition data for vitamin D in the USDA National Nutrient Database for Standard Reference are being updated and expanded, focusing on high priority foods and validated analytical methodology. A lack of certified reference materials and analytical methods validated for these key foods required the development of five matrix-specific control composite materials (CC) (canned salmon and vitamin D 3 fortified cereal, orange juice, milk, and cheese). Each of six experienced laboratories (research and commercial) analyzed vitamin D 3 in five subsamples of each CC in five separate analytical batches, with one subsample of each material in each run. Research laboratories performed recovery studies, mass spectrometric analysis, and other studies to validate quantitation in each matrix. Initial results showed a wide disparity between the six laboratories (RSDs of 26-46%). Extensive collaboration resolved several problems related to calibration standards, extraction solvents and the internal standard, achieving final values with RSDs of approximately 10%, validated by mass spectrometry tests that confirmed lack of matrix interferences in these foods.

A method has been developed for the simultaneous determination of traces of Fe(III) and Fe(II) in water by on-line coupling of spectrophotometry with flame atomic absorption spectrometry (FAAS). The method involves cloud-point extraction (CPE) of both species with ammonium pyrrolidinecarbodithioate (APDC) under standard conditions, which facilitates the in situ complexation and extraction of both species. Differentiation of the oxidation states of iron is achieved by using mathematical equations to overcome the interference of Fe(III) in the spectrophotometric determination of Fe(II) when they are both present in the same solution. In this manner the timeconsuming and labor-intensive steps of preoxidation of Fe(II) or reduction of Fe(III) are eliminated. By preconcentrating a 10-mL sample solution detection limits as low as 7 µg L -1 , were obtained after a single-step extraction procedure. The relative standard deviation (n=4, 30 µg L -1 ) was 2.6% and 1.8% for spectrophotometry and FAAS, respectively. Recoveries in the range of 96-105% were obtained by analysis of spiked real samples. The method was further verified by analyzing a certified reference material (IMEP-9); for this the recovery was 98.5%.

The total concentration of arsenic in different foods from southeast Spain was determined by hydride generation atomic absorption spectrometry. Mineralization was carried out with an HNO 3-HClO 4 mixture in a thermostated sand bath. Arsenic determination was performed by the standard addition method. Analyses of NIST and CBR-CEC reference materials demonstrated the reliability and accuracy of the technique. The highest arsenic levels were found in seafood, cereals, meat and meat by-products. In meat and meat by-products, the total arsenic measured in meat was significantly higher than that in sausages (p<0.05). In cereals, arsenic concentrations in corn and white rice samples were significantly higher (p<0.01) than those measured in wheat by-products. Mean arsenic concentrations in cheese were statistically lower than those in other dairy products (p<0.01). New data have been provided on the total arsenic content of a variety of foods in Spain, which is important for making exposure estimates. The estimated daily intake of total arsenic in the Spanish diet was 221 g As day À1 .

Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish were proposed after careful optimization of chemical and instrumental parameters for Hg measurement by cold vapor (CV)/hydride generation (HG) atomic absorption spectrometry (AAS) and CV/HG inductively coupled plasma atomic emission spectrometry (ICP-AES). Quantitative extraction of Hg species avoiding any interspecies conversion was achieved by fast microwave assisted solubilization of fish tissue with relatively low amount of tetramethylammonium hydroxide (TMAH) or 6 mol L − 1 HCl. After careful optimization of chemical parameters selective determination of Hg 2+ in the presence of excess of methylmercury is attained by using continuous flow CV AAS, 1% m/V SnCl 2 as reductant and 0.1 mol L − 1 HCl as reaction medium. Simple calibration curve prepared with aqueous standard of Hg 2+ is recommended for its quantification. Both Hg 2+ and methylmercury could be determined simultaneously with equal sensitivity by CV/HG ICP-AES directly in the diluted TMAH solution obtained after extraction with 1% m/ V NaBH 4 as reductant. Quantification of the sum of Hg 2+ and methylmercury against calibration curve prepared with aqueous standard of methylmercury is suggested. It should be mentioned that batch hydride generation system with quartz tube heated in air/acetylene flame could also be used for simultaneous determination of both Hg species in fish extracts, with standard additions calibration. The validity of the developed analytical procedures for selective determination of Hg 2+ and methylmercury (by difference between the total Hg and Hg 2+ ) is confirmed by the analyses of certified reference material DOLT-1 and reference material IMEP-20. Very close agreement between certified values and analytical results was found.

Simple and rapid analytical procedures for the determination of Hg 2+ and methylmercury in fish were proposed after careful optimization of chemical and instrumental parameters for Hg measurement by cold vapor (CV)/hydride generation (HG) atomic absorption spectrometry (AAS) and CV/HG inductively coupled plasma atomic emission spectrometry (ICP-AES). Quantitative extraction of Hg species avoiding any interspecies conversion was achieved by fast microwave assisted solubilization of fish tissue with relatively low amount of tetramethylammonium hydroxide (TMAH) or 6 mol L − 1 HCl. After careful optimization of chemical parameters selective determination of Hg 2+ in the presence of excess of methylmercury is attained by using continuous flow CV AAS, 1% m/V SnCl 2 as reductant and 0.1 mol L − 1 HCl as reaction medium. Simple calibration curve prepared with aqueous standard of Hg 2+ is recommended for its quantification. Both Hg 2+ and methylmercury could be determined simultaneously with equal sensitivity by CV/HG ICP-AES directly in the diluted TMAH solution obtained after extraction with 1% m/ V NaBH 4 as reductant. Quantification of the sum of Hg 2+ and methylmercury against calibration curve prepared with aqueous standard of methylmercury is suggested. It should be mentioned that batch hydride generation system with quartz tube heated in air/acetylene flame could also be used for simultaneous determination of both Hg species in fish extracts, with standard additions calibration. The validity of the developed analytical procedures for selective determination of Hg 2+ and methylmercury (by difference between the total Hg and Hg 2+ ) is confirmed by the analyses of certified reference material DOLT-1 and reference material IMEP-20. Very close agreement between certified values and analytical results was found.

A comparison is presented of six methods involving nitric acid in conjunction with other reagents to digest three certified marine biological samples (DOLT-3, DORM-3, IAEA-407) and a fish bone homogenate (prepared from Merluccius australis). An inductively coupled plasma-mass spectrometer with an octopole collision cell was used to determine up to 40 elements (Li, U) in the digests. These results were assessed in terms of their accuracy and precision, and a flow chart was developed to aid the selection of the optimal digestion method. Although none of the methods was found to give accurate determinations for all elements in the different reference materials, a relatively simple method involving nitric acid and hydrogen peroxide heated in a domestic microwave oven gave the most acceptable results. (B.M. Peake).

The ef®ciency of different digestion methods (six microwave decomposition methods and a wet acid digestion method) in the solubilisation of six metals (Cr, Ni, Cu, Pb, Cd, Zn), for their determination in¯y ashes, was compared. Five different mineral acid mixtures and two different microwave systems were tested. The study was carried out by analyzing two highly homogenised¯y ash samples (from sewage sludge and city waste incineration) provided by the Joint Research Centre of Ispra. Determinations were performed by atomic absorption spectrometry and by inductively coupled plasma atomic emission spectrometry. The analytical performance of the laboratory was evaluated using the 1633a Coal Fly Ash Standard Reference Material of National Bureau of Standards (NBS SRM 1633a).

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 A1, Ca, C1, 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.

The calibration of Karl Fischer instruments and reagents and the compensation for instrumental bias are essential to the accurate measurement of trace levels of water in organic and inorganic chemicals. A stable, nonhygroscopic standard, Water Saturated Octanol, which is compatible with the Karl Fischer reagents, has been prepared. This material, Standard Reference Material (SRM) 2890, is homogeneous and is certified to contain 39.24 +/- 0.85 mg water/mL (expanded uncertainty) of solution (47.3 +/- 1.0 mg water/g solution, expanded uncertainty) at 21.5 degrees C. The solubility of water in -octanol has been shown to be nearly constant between 10 degrees C and 30 degrees C (i.e., within 1% of the value at 21.5 degrees C). The results of an interlaboratory comparison exercise illustrate the utility of SRM 2890 in assessing the accuracy and bias of Karl Fischer instruments and measurements.

For the past 25 years the National Institute of Standards and Technology (NIST) has developed certified reference materials (CRMs), known as standard reference materials (SRMs), for determination of organic contaminants in environmental matrices. Assignment of certified concentrations has usually been based on combining results from two or more independent analytical methods. The first-generation environmental-matrix SRMs were issued with certified concentrations for a limited number (5 to 10) of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Improvements in the analytical certification approach significantly expanded the number and classes of contaminants determined. Environmental-matrix SRMs currently available include air and diesel particulate matter, coal tar, marine and river sediment, mussel tissue, fish oil and tissue, and human serum, with concentrations typically assigned for 50 to 90 organic contaminants, for example PAHs, nitro-substituted PAHs, PCBs, chlorinated pesticides, and polybrominated diphenyl ethers (PBDEs).

The economic and geological importance of platinum group of elements has led to the development of analytical methods to quantify them in different types of samples. In the present paper the quantitative information for spectral interference in radial viewing 40.68 MHz inductively coupled plasma atomic emission spectrometry in the determination of Pt, Pd and Rh in the presence of complex matrix, containing Al, Ca, Fe, Mg, Mn, P and Ti as matrix constituents was obtained. The database was used for optimum line selections. By using the selected analysis lines the following detection limits in ng g − 1 were obtained: Pt 1700, Pd-1440, Rh-900. The reached detection limits determine the possibilities and limitation of the direct ICP-AES method in the determination of Pt, Pd and Rh in geological and environmental materials. The database for spectral interferences in the presence of aluminum can be used for the determination of platinum group of elements in car catalysts. The accuracy of the analytical results was experimentally demonstrated by two certified reference materials that were analyzed: SARM 7, Pt ore and recycled auto-catalyst certified reference material SRM 2556.

Increasing numbers of clinical laboratories are transitioning away from flame and electrothermal AAS methods to those based on ICP-MS. Still, for many laboratories, the choice of instrumentation is based upon (a) the element(s) to be determined, (b) the matrix/matrices to be analyzed, and (c) the expected concentration(s) of the analytes in the matrix. Most clinical laboratories specialize in measuring Se, Zn, Cu, and Al in serum, and/or Pb, Cd, Hg, As, and Cr in blood and/or urine, while other trace elements (e.g., Pt, Au etc.) are measured for therapeutic purposes. Quantitative measurement of elemental species is becoming more widely accepted for nutritional and/or toxicological screening purposes, and ICP-MS interfaced with separation techniques, such as liquid chromatography or capillary electrophoresis, offers the advantage of on-line species determination coupled with very low detection limits. Polyatomic interferences for some key elements such as Se, As, and Cr require instrumentation equipped with dynamic reaction cell or collision cell technologies, or might even necessitate the use of sector field ICP-MS, to assure accurate results. Nonetheless, whatever analytical method is selected for the task, careful consideration must be given both to specimen collection procedures and to the control of pre-analytical variables. Finally, all methods benefit from access to reliable certified reference materials (CRMs). While a variety of reference materials (RMs) are available for trace element measurements in clinical matrices, not all can be classified as CRMs. The major metrological organizations (e.g., NIST, IRMM, NIES) provide a limited number of clinical CRMs, however, secondary reference materials are readily available from commercial organizations and organizers of external quality assessment schemes.

Robust and validated analytical methods are needed for the implementation of GM-food and feed legislation. The validation, based on the characterisation of a method for its sensitivity, accuracy and precision, is performed in-house or in collaborative trials according to good laboratory practice to comply with internationally harmonised standards. The way in which this is implemented depends on the analyte, influences of the food/feed matrix and other requirements that need to be met. Certified reference materials, when matrix matches and contains the appropriate concentration of the certified analyte, are a useful tool in validation. Some acceptability criteria, associated to ad-hoc statistics (e.g. percent bias, repeatability and reproducibility) are useful for the purposes of testing and decision-making. However, the interpretation of validation results also depends on professional judgment and expertise. In such respect, fuzzy logic-based techniques (complementary to conventional statistics) are advocated to support the continuous progress of GMO science and routine laboratory analyses.

Eight heavy metals, namely Cu, Zn, Fe, Mn, Cd, Ni, Pb and As, in nine varieties of edible vegetable oils collected from China were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and graphite furnace atomic absorption spectrometry (GF-AAS) after microwave digestion. The accuracy of procedure was confirmed by certified reference materials (GBW10018 and GBW08551). The relative standard deviations were found below 10%. The concentrations for copper, zinc, iron, manganese, nickel, lead and arsenic were observed in the range of 0.214-0.875, 0.742-2.56, 16.2-45.3, 0.113-0.556, 0.026-0.075, 0.009-0.018 and 0.009-0.019 lg g À1 , respectively. Cadmium was found to be 2.64-8.43 lg/kg. In general, iron content was higher than other metals in the investigated edible vegetable oils.

A sample preparation method based on sintering, followed by analysis by inductively coupled plasma-sector field mass spectrometry (ICP-SFMS) for the simultaneous determination of chloride and bromide in diverse and mixed solid wastes, has been evaluated. Samples and reference materials of known composition were mixed with a sintering agent containing Na(2)CO(3) and ZnO and placed in an oven at 560 degrees C for 1h. After cooling, the residues were leached with water prior to a cation-exchange assisted clean-up. Alternatively, a simple microwave-assisted digestion using only nitric acid was applied for comparison. Thereafter the samples were prepared for quantitative analysis by ICP-SFMS. The sintering method was evaluated by analysis of certified reference materials (CRMs) and by comparison with US EPA Method 5050 and ion chromatography with good agreement. Median RSDs for the sintering method were determined to 10% for both chlorine and bromine, and median recovery to 96% and 97%, respectively. Limits of detection (LODs) were 200mg/kg for chlorine and 20mg/kg for bromine. It was concluded that the sintering method is suitable for chlorine and bromine determination in several matrices like sewage sludge, plastics, and edible waste, as well as for waste mixtures. The sintering method was also applied for determination of other elements present in anionic forms, such as sulfur, arsenic, selenium and iodine.

GMO protein content in maize flours or fresh crops can be easily assessed by the enzyme-linked immunosorbent assays (ELISA) and immunochromatographic (lateral flow) strip tests commercially available. Therefore, ELISA can be seen as a useful tool for screening, for control purposes and for traceability implementation. In order to highlight the importance of monitoring GMO protein presence in food products and to investigate the performance of representative ELISA commercial kits, we evaluated three commercial kits by measuring the amount of Cry1Ab/Cry1Ac in IRMM certified reference materials.

The paper reproduces a talk given at a two day symposium on quality assurance in chemistry held in Brisbane, Australia in 2005. Intended for an audience of analysts in the field the theme of the symposium drew inspiration from the series of books by Douglas Adams "The Hitchhiker's Guide to the Galaxy". An introduction to basic concepts of metrological traceability is followed by a discussion of practical steps to ensure metrological traceability of field measurement results. The relationship between metrological traceability and comparability of measurement results is discussed. To achieve metrological traceability in the field the use of appropriate certified reference materials for calibration is recommended. Examples of atmospheric carbon dioxide and roadside breathalyser measurements are given.

Certified reference materials (CRMs) enable the meaningful comparison of measurement results over time and place. When CRMs are used to calibrate or verify the performance of a measurement system, results produced by that system can be related through the CRM to well-defined, stable, and globally accessible reference(s). Properly done, this directly establishes the metrological traceability of the results. However, achieving the meaningful comparison of results from measurement systems calibrated and/or verified with different CRMs requires that the different materials truly deliver the same measurand, that is, are "the same" within stated uncertainty except for differences in the level of the analyte of interest. We here detail experimental and data analysis techniques for establishing and demonstrating the comparability of materials. We focus on (1) establishing a uniform interpretation of the common forms of CRM uncertainty statements, (2) estimating consistent measurement system response uncertainties from sometimes inconsistent experimental designs, (3) using "errors-in-variables" analysis methods to evaluate comparability studies and novel graphical tools for communicating results of the evaluation to reviewing authorities and potential CRM customers, and (4) augmenting established comparability studies with new materials using measurements provided by the certifying institution. These experimental and data analytic tools were developed in support of the Joint Committee for Traceability in Laboratory Medicine's efforts to enhance the reliability of clinical laboratory measurements and are illustrated with potassium and cholesterol measurands of clinical relevance; however, these tools can be applied to any group of materials that deliver the same nominal measurand with stated value and uncertainty.

A metrological background for the selection and use of proficiency testing (PT) schemes for a limited number N of laboratories-participants (less than 20-30) is discussed. The following basic scenarios are taken into account: (1) adequate matrix certified reference materials (CRM) or in-house reference materials (IHRM) with traceable property values are available for PT use as test items; (2) no appropriate matrix CRM is available, but a CRM or IHRM with traceable property values can be applied as a spike or similar; (3) only an IHRM with limited traceability is available. The discussion also considers the effect of a limited population of PT participants N p on statistical assessment of the PT results for a given sample of N responses from this population. When N p is finite and the sample fraction N/N p is not negligible, a correction to the statistical parameters may be necessary. Scores suitable for laboratory performance assessment in such PT schemes are compared.