Method validation and reference materials

For implementation of food and feed legislation, there is a strong need for development and harmonisation of reliable, validated and if possible, robust and simple analytical methods. In addition, precise methods used for measuring the exposure of humans to certain types of food contaminants and residues (natural, man-made or produced during technological treatment) such as, e.g. mycotoxins, acrylamide, pesticides and allergens have to be available, in order to compare results derived from monitoring studies. Methods should be validated (in-house or in a collaborative trial) according to harmonised protocols and good laboratory practice must be in place in order to be compliant with internationally harmonised standards. The way in which this is implemented depends strongly on the analyte, interference within the food matrix and other requirements that need to be met. Food and feed certified reference materials, when matrix matched and containing the appropriate concentration of the certified substance, are an extremely useful tool in validation of measurements.Presented at BERM-9—Ninth International Symposium on Biological and Environmental Reference Materials, 15–19 June 2003, Berlin, Germany.     

Harmonisation Of Ec Air Quality Directives

Abstract

The Environment Institute of the Joint Research Centre in Ispra devotes an important part of its activities to support the Commission of the European Communities in scientific and technical matters. As an example of these activities, a general overview is given of the harmonisation work lead by its Central Laboratory of Air Pollution for the implementation of EC air quality directives in the European Member States. The different stages of a directive's development are reviewed and illustrated with typical examples of harmonisation work recently undertaken.

Preparatory actions for future regulations are illustrated by the recent intercomparison exercise for VOC measurements, realized in view of the coming directive on photo-oxidants.

Quality assurance programmes are developed that are mainly focused on the evaluation of sampling, calibration and measurement techniques in the Member States. Special attention is also paid to the harmonisation of network design. The results of a recent network design campaign realised in Madrid, using passive sampling techniques in combination with mobile measurements, are presented.

An example of the development of scientific and technical progress is given by the intercomparison of primary NO₂ calibration standards, where the reference method of the directive was checked and compared to new standard methods.     

Determination of iodine-129 and iodine-127 in environmental samples collected in Japan

Analytical method for the determination of¹²⁹I and¹²⁷I in environmental samples has been developed by using radiochemical neutron activation analysis. The¹²⁹I levels in the samples such as soil (0.9–41 mBq/kg), precipitation (0.002–0.11 mBq/kg), pine needles (1.2–32 mBq/kg) and seaweed (<0.1–17 mBq/kg) collected near the nuclear facilities in Tokaimura were higher than those from the other areas in Japan. The highest¹²⁹I concentration was found in surface soil (0–5 cm), and the highest¹²⁹I/¹²⁷I ratios were found in pine needles and precipitation. The¹²⁹I/¹²⁷I ratio was higher in rice paddy soil than those in wheat field soil collected around Tokaimura, while the concentration of¹²⁹I somewhat higher in wheat field soil.     

Immobilization of Urease and Cholinesterase on the Surface of Semiconductor Transducer for the Development of Light-Addressable Potentiometric Sensors

Various methods for the immobilization of urease and butyrylcholinesterase on the insulator surface of a laser-scanned semiconductor transducer (LSST) have been tested and compared for the development of an enzyme-based light-addressable potentiometric sensor (LAPS). The method of preparing photocurable membranes on LAPS is presented, and a new type of enzyme LAPS with photocurable polymeric enzyme membranes has been elaborated. It was found that sensors prepared by means of covalent bonding and cross-linking with inactive protein (type SIII) and with photocurable membrane matrices (type SIV) are more prospective. The enzyme LAPSensors with photocurable membranes demonstrate a degree of sensitivity close to the theoretical value and working ranges of 6.3·10^–5–1.1·10^–2 and 1·10^–4–1·10^–1molL^–1 urea for acrylamide and acrylate-based membrane matrices, respectively, and 2.5·10^–4–2·10^–1molL^–1 butyrylcholine for an acrylamide membrane matrix. It is shown that such sensors can be also used for the analysis of enzyme inhibitors.     

Some aspects of environmental radioactivity around the former Soviet Union"""s Semipalatinsk nuclear test site: Local fallout Pu in Ust"""-Kamenogorsk district

The ¹³⁷Cs, ²³⁸Pu and ^239,240Pu activity concentrations were determined together with the atomic ratios of ²⁴⁰Pu/²³⁹Pu for the soil samples at 19 sites from the Ust"-Kamenogorsk district, located more than 300 km east of the Semipalatinsk nuclear test site (SNTS). The mean areal deposition of ¹³⁷Cs ranged from 1,500 to 4,100 Bq/m². However, some hot spot-like areas showing high concentrations of 5,500–7,700 Bq/m² were foundat some sites within the city. The ^239,240Pu levels ranged from <50 to 510 Bq/m², however most of them ranged between 120–200 Bq/m². These levels are nearly the same as those around the Semipalatinsk City. At most of the sites within the city and its adjacent areas, both nuclides were found in the soil layers up to a depth of 30 cm. A fraction of 20–50% of ^239,240Pu was not leached by hot digestion with concentrated HNO₃ containing a small amount of H₂O₂. Generally, such tightly bound fraction showed a trend to decrease with increasing distance from the SNTS. The fraction of these radionuclides that were deposited in Ust"-Kamenogorsk district from global and from SNTS fallouts have been determined using the ²⁴⁰Pu/²³⁹Pu atomic ratios in both Pu fractions: one which can be leached with hot HNO₃ + H₂O₂ and another that is a non-leacheable for each soil layer of core samples. As a result a fraction of 21–80% (mostly 30–60%) of total ^239,240Pu were found to be due to the local fallout of Pu from the SNTS debris. For ¹³⁷Cs, the contribution (mostly 10–20%) of local fallout from the SNTS were estimated to be far lower as compared to ^239,240Pu.     

Experimental design-based development and single laboratory validation of a capillary zone electrophoresis method for the determination of the artificial sweetener sucralose in food matrices

A capillary zone electrophoresis (CZE) method, optimised chemometrically, underwent a complete in-house validation protocol for the qualification and quantification of sucralose in various foodstuffs. Separation from matrix components was obtained in a dinitrobenzoic acid (3 mM)/sodium hydroxide (20 mM) background electrolyte with a pH of 12.1, a potential of 0.11 kV cm^–1 and a temperature of 22 °C. Detection was achieved at 238 nm by indirect UV. Screening, optimisation and robustness testing were all carried out with the aid of experimental design. Using standard addition calibration, the CZE method has been applied to still, carbonated and alcoholic beverages, yoghurts and hard-boiled candy. The method allows the detection of sucralose at >30 mg kg^–1, with a linearity range of 50–500 mg kg^–1, making it suitable for implementation of the recently amended Sweeteners for use in foodstuffs Directive (European Parliament and Council (2003) Off J L237:3–12), which set maximum usable doses of sucralose for many foodstuffs, most ranging from 200 mg kg^–1 to 450 mg kg^–1.     

Determination of I-129 and I-127 in soil and tracer experiments on the adsorption of iodine on soil

Neutron activation analysis of¹²⁹I and¹²⁷I in soil has been studied. The limit of detection for¹²⁹I in soil was about 0.05 mBq/kg or 1×10^–9 as¹²⁹I/¹²⁷I atom ratio. The range of¹²⁹I concentration in surface soils collected around Tokaimura (Ibaraki Prefecture) was 0.9–41 mBq/kg.Tracer experiments on the adsorption of iodine were also carried out, in order to obtain information on the behaviour of iodine in soil-water systems. Different adsorption patterns of iodide and iodate on soil were found. It was supposed that iodide was adsorbed by the soil fraction which became unstable at about 200° C and iodate by the fraction which was relatively stable to heating.     

Direct Quantitation of Phytocannabinoids by One-Dimensional 1H qNMR and Two-Dimensional 1H-1H COSY qNMR in Complex Natural Mixtures

The widespread use of phytocannabinoids or cannabis extracts as ingredients in numerous types of products, in combination with the legal restrictions on THC content, has created a need for the development of new, rapid, and universal analytical methods for their quantitation that ideally could be applied without separation and standards. Based on previously described qNMR studies, we developed an expanded ¹H qNMR method and a novel 2D-COSY qNMR method for the rapid quantitation of ten major phytocannabinoids in cannabis plant extracts and cannabis-based products. The ¹H qNMR method was successfully developed for the quantitation of cannabidiol (CBD), cannabidiolic acid (CBDA), cannabinol (CBN), cannabichromene (CBC), cannabichromenic acid (CBCA), cannabigerol (CBG), cannabigerolic acid (CBGA), Δ9-tetrahydrocannabinol (Δ9-THC), Δ9-tetrahydrocannabinolic acid (Δ9-THCA), Δ8-tetrahydrocannabinol (Δ8-THC), cannabielsoin (CBE), and cannabidivarin (CBDV). Moreover, cannabidivarinic acid (CBDVA) and Δ9-tetrahydrocannabivarinic acid (Δ9-THCVA) can be distinguished from CBDA and Δ9-THCA respectively, while cannabigerovarin (CBGV) and Δ8-tetrahydrocannabivarin (Δ8-THCV) present the same ¹H-spectra as CBG and Δ8-THC, respectively. The COSY qNMR method was applied for the quantitation of CBD, CBDA, CBN, CBG/CBGA, and THC/THCA. The two methods were applied for the analysis of hemp plants; cannabis extracts; edible cannabis medium-chain triglycerides (MCT); and hemp seed oils and cosmetic products with cannabinoids. The ¹H-NMR method does not require the use of reference compounds, and it requires only a short time for analysis. However, complex extracts in ¹H-NMR may have a lot of signals, and quantitation with this method is often hampered by peak overlap, with 2D NMR providing a solution to this obstacle. The most important advantage of the COSY NMR quantitation method was the determination of the legality of cannabis plants, extracts, and edible oils based on their THC/THCA content, particularly in the cases of some samples for which the determination of THC/THCA content by ¹H qNMR was not feasible.     

Synthesis of 4,6-dinitro-3-R-benzo[d]isoxazoles and their transformations under the action of nucleophiles

A new procedure was developed for the preparation of 4,6-dinitro-3-R-benzo[d]isoxazoles (R are derivatives of the aldehyde group) based on 2,4,6-trinitrophenylacetaldehyde. The resulting compounds are characterized by the regiospecific substitution of the nitro group at position 4 under the action of anionic nucleophiles RS^–, RO^–, F^–, or N₃ ^–, which allowed the development of a new method for the preparation of previously unknown 4-Nu-6-nitro-3-R-benzo[d]isoxazoles (Nu is the residue of a nucleophile). At the same time, oxidative nucleophilic substitution under the action of anions of some -dicarbonyl compounds leads to the replacement of the hydrogen atom at position 7 with the corresponding C-nucleophiles.     

Activation Enthalpy and Entropy for the Decay of 9-Cyanophenanthrene Exciplexes

Activation parameters were studied for the decay of 9-cyanophenanthrene exciplexes with some weak electron donors (the Gibbs energy of electron transfer G ^* _et ranging from –0.02 to –0.09 eV), which displayed fairly high emission in both nonpolar and polar aprotic solvents. It was shown that the activation enthalpy of decay for the exciplexes is low, while the activation entropy reaches –(100–150) J mol^–1 K^–1, which is consistent with the two possible decay mechanisms: by dissociation into free radical ions or by intersystem crossing into the triplet state.     

Determination of pyrimethanil and kresoxim-methyl in soils by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A method using headspace solid-phase microextraction (HS-SPME) then gas chromatography–mass spectrometry with selected ion monitoring (GC–MS, SIM) has been developed for determination of trace amounts of the fungicides pyrimethanil and kresoxim-methyl in soil and humic materials. Both fungicides were extracted on to a fused-silica fibre coated with 85 m polyacrylate (PA). Response-surface methodology was used to optimise the experimental conditions. For soil samples the linear dynamic range of application was 0.004–1.000 g g^–1 for pyrimethanil and 0.013–1.000 g g^–1 for kresoxim-methyl. The detection limits were 0.001 g g^–1 and 0.004 g g^–1 for pyrimethanil and kresoxim-methyl, respectively. HP-SPME–GC–MS analysis was highly reproducible—relative standard deviations (RSD) were between 6.7 and 12.2%. The method was validated by analysis of spiked matrix samples and used to investigate the presence of pyrimethanil and kresoxim-methyl above the detection limits in soil and humic materials.     

Examination of the modified monostandard method in neutron activation analysis

The reproducibility, the small scale as well as the large scale variability of¹³⁷Cs extracted sequentially from the soil by using a modified Tessier procedure was investigated at several grassland sites in Bavaria/Germany and in the Chemobyl area. Because undisturbed grassland soils are never homogeneous with respect to their soil properties, all sequential extractions at the German sites were carried out at each plot separately for different soil layers (e.g., 0–2, 2–5, 5–10, 10–15, 15–20 and 20–30 cm). The results show that the coefficients of variation (CV) for the reproducibility of the extraction procedure for¹³⁷Cs was (with some exceptions) around 10–20% for all fractions. For the small scale variability of¹³⁷Cs (samples within an area of 10×10m²) the values for theCV were (again with a few exceptions) in the same range. Compared to that, the large scale variability of extractable¹³⁷Cs (random soil samples within an area of 100×200 km²) was higher for all fractions, even though only moderately. The implications of these results with respect to a sampling design are discussed.     

Voltammetric behaviour of the zirconium-phenylfluorone-hexadecyl pyridinium chloride system and the sensitizing effect of surfactants

The adsorptive voltammetric features of the zirconium-phenylfluorone (PF)-hexadecyl pyridinium chloride (CPC) system has been investigated. A sensitizing effect of the surfactant CPC on the adsorption current of the Zr-PF-CPC system were observed by linear potential sweep voltammetry. A new sensitive method determining Zr traces was established, the detection limit and linear relationship is 5.0×10^–9 mol/l and 7.7×10^–9–1.1×10^–7 mol/l, respectively. This method has been applied to mineral samples.     

The monostandard method in thermal neutron activation analysis of geological, biological and environmental materials

Summary A simple method is decribed for instrumental multielement thermal neutron activation analysis using a monostandard. For geological and air dust samples, iron is used as a comparator, while sodium has advantages for biological materials.To test the capabilities of this method, the values of the effective cross sections of the 23 elements determined were evaluated in a reactor site with an almost pure thermal neutron flux of about 9·10¹² n·cm^–2·s^–1 and an epithermal neutron contribution of less than 0.03%. The values obtained were found to agree mostly well with the best literature values of thermal neutron cross sections. The results of an analysis by activation in the same site agree well with the relative method using multielement standards and for several standard reference materials with certified element contents. A comparison of the element contents obtained by the monostandard and relative methods together with corresponding precisions and accuracies is given.

---

Die Monostandardmethode bei der Aktivierungsanalyse mit thermischen Neutronen von geologischem, biologischem und Umweltmaterial

Zusammenfassung Die Monostandardmethode wurde erstmals auf die Aktivierungsanalyse mit rein thermischen Neutronen aus der thermischen Säule des Reaktors FRJ-2 (mit epithermischen Anteilen von < 0,03%) angewendet. Hier sind die theoretischen Verhältnisse und damit auch Gleichungen besonders einfach. — Die bei einem Neutronenfluß von 9·10¹² n·cm^–2·s^–1 ermittelten effektiven Neutroneneinfangquerschnitte stimmen häufig gut mit den Literaturwerten überein. — Für geologische Proben wurde Eisen, für biologisches Material Natrium als Komparator, d.h. Monoelementstandard, verwendet. Es konnten über zwanzig Elemente in Andesit, Granit, Flugstaubasche, Luftstaub, Pflanzenmaterial und Obstblättern bestimmt werden.

---

---

Dedicated to Professor Dr. Kurt Starke, University of Marburg/ Lahn on the occasion of his 70 th birthday

---

Fourth Communication on Improvement of Instrumental Analysis for Service Analysis

---

Guest Scientist from Egypt.

---

Guest Scientist under IAEA-Fellowship from the Faculty of Chemistry, University of Sofia, Bulgaria

---

This paper is an extract of the more detailed Report Jül-1822 (ISSN 0366-0885), January 1983.     

Homogeneous liquid-liquid extraction combined with gas chromatography-electron capture detector for the determination of three pesticide residues in soils

In this study, a new method was developed for analyzing malathion, cypermethrin and lambda-cyhalothrin from soil samples by using homogeneous liquid–liquid extraction (HLLE) and gas chromatography with electron capture detector (GC–ECD). Acetone was used as extraction solvent for the extraction of target pesticides from soil samples. When the extraction process was finished, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to carbon tetrachloride, using HLLE. Under the optimum conditions, linearity was obtained in the range of 0.05–40 μg kg⁻¹ for malathion, 0.04–10 μg kg⁻¹ for lambda-cyhalothrin and 0.05–50 μg kg⁻¹ for cypermethrin, respectively. Coefficients of correlation (r²) ranged from 0.9993 to 0.9998. The repeatability was carried out by spiking soil samples at concentration levels of 2.5 μg kg⁻¹ for lambda-cyhalothrin, and 10 μg kg⁻¹ for malathion and cypermethrin, respectively. The relative standard deviations (RSDs) varied between 2.3 and 9.6% (n = 3). The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, varied between 0.01 and 0.04 μg kg⁻¹. The relative recoveries of three pesticides from soil A1, A2 and A3 at spiking levels of 2.5, 5 and 10 μg kg⁻¹ were in the range of 82.20–91.60%, 88.90–110.5% and 77.10–98.50%, respectively. In conclusion, the proposed method can be successfully applied for the determination of target pesticide residues in real soil samples.     

Study on the colour reaction of Te-KI-RhB system in the presence of PVA-OP

A new supersensitive spectrophotometric method for the determination of tellurium (IV) has been developed which is based on the formation of an ion-association complex with potassium iodide and rhodamine B (RhB) in the presence of polyvinyl alcohol (PVA) and polyethylene glycol octyl phenyl ether (OP). The molar absorptivity at 560 nm is 2.8 × 10⁶ 1 mol^–1 cm^–1. Beer's law is obeyed over the range of 20–70 ng/ml Te. The method has been applied successfully to determine tellurium in alloy, steel and some other samples.     

Harmonisation of proficiency testing schemes

The harmonisation of proficiency testing (PT) schemes has been under debate for a long time. There are obvious reasons why harmonisation of the practices in PT would be beneficial. In many areas, there is still a belief that further harmonisation of practices in PT would improve the comparability of measurement data. In particular when two laboratories are to be compared that have not participated in a single PT, problems arise which allegedly can be overcome by further harmonisation of PT schemes. In practice, however, parties involved in PT are not always embracing the idea of harmonisation. With the results of two European projects in mind, a discussion is given on harmonisation aspects, and some considerations are given that may help to decide in practice whether harmonisation is likely to solve particular problems. The first project, the European Proficiency Testing Network (EPTN), is concerned with further harmonisation. The second European project (COEPT) aims at providing a basis to assess equivalence across proficiency tests, and explores the conditions under which such an assessment is feasible.

     

Physicochemical Speciation of Americium in Soils from Rocky Flats, Colorado, USA

The objective of the research was to characterize the ²⁴¹Am distribution in six operationally defined chemical and mineralogical phases of soil samples taken from the Rocky Flats Environmental Technology Site (RFETS). Soil samples were subjected to selective sequential fractionation procedures to determine ²⁴¹Am association with the soluble, exchangeable, carbonate, organic, sesquioxide and silicate fractions. The highest percentage of ²⁴¹Am was found to be associated with the sesquioxide (hydrous oxide) fraction (39–47%), with lesser amounts in the soluble (14–17%), exchangeable (4–9%), carbonates (4–17%), organic (3–13%), and silicate (10–21%) soil fractions. Differences between americium and plutonium association with various soil fractions were observed.     

Intercomparison and determination of environmental standard samples by instrumental neutron activation analysis

To identify and improve the analytical technique for air pollution research, four kinds of environmental standard samples, i.e., airbome particulate matter, coal flyash, soil and pine needle supplied from the NIST and the IAEA were analyzed using thermal and epithermal neutron activation techniques. Sample irradiation was done at the irradiation facilities (neutron flux, 1 · 10¹³ n·cm^–2·s^–1) of the TRIGA MARK-III Research Reactor in the Korea Atomic Energy Research Institute. The accuracy and precision for the analysis of 40 trace and toxic elements in the samples were compared with the certified and reported values, respectively. In the analytical results of all standard reference materials, the relative standard deviation were within the 15% except for 11 elements and the relative error were agreed within the 10–20% except for 13 elements. The benefit of epithermal activation was investigated and the optimum analytical condition is reported.     

Interference of humic substances on the speciation analysis of inorganic selenium in waters and soils by DPCSV

A speciation scheme allowing the study of selenium speciation in environmental samples has been developed in order to study the transfer mechanism in the system water/soil/plant/animal. This scheme is based on a set of sample treatment procedures followed by Se(IV) determination by Differential Pulse Cathodic Stripping Voltammetry (DPCSV). Se(IV) may be determined with a detection limit close to 25 ng l^–1 and a linear response in the range 25–4000 ng l^–1. However, humic substances, present in some natural waters and soils, which are adsorbed at the mercury drop electrode (HMDE) surface may alter the signal. This may be caused by a competition between adsorption of organic matter and mercury(II) selenide formation at the electrode surface. As a consequence the detection limit has been increased to ca. 250 ng l^–1 in the presence of 1 mg l^–1 fulvic acids; the linear response range is then shifted to 250–10000 ng l^–1. After an extensive study of these interferences and using standard additions procedures, the Se(IV) content of various waters and soil extracts has been determined by DPCSV with a good reproducibility (RSD about 1%). Accuracy is satisfactory comparing the results obtained by DPCSV to those obtained by Hydride Generation/Quartz Furnace Absorption Atomic Spectrometry (HG/QFAAS).