Investigate the capability of INAA absolute method to determine the concentrations of 238U and 232Th in rock samples

This work aimed to study the capability of INAA absolute method in determining the elemental concentration of ²³⁸U and ²³²Th in the rock samples. The INAA absolute method was implemented in PUSPATI TRIGA Mark II research reactor, Malaysian Nuclear Agency (NM). The accuracy of INAA absolute method was performed by analyzing the IAEA certified reference material (CRM) Soil-7. The analytical results showed the deviations between experimental and certified values were mostly less than 10 % with Z-score in most cases less than 1. In general, the results of analysed CRM Soil-7 show a good agreement between certified and experimental results which mean that the INAA absolute method can be used accurately for elemental analysis of uranium and thorium in various types of samples. The concentration of ²³⁸U and ²³²Th ranged from 1.77 to 24.25 and 0.88 to 95.50 ppm respectively. The highest value of ²³⁸U and ²³²Th was recorded for granite rock sample G17 of ²³⁸U and sample G9 of ²³²Th, whereas the lower value was 1.77 ppm of ²³⁸U recorded in sandstone rock and 0.88 ppm of ²³²Th for gabbro. Moreover, a comparison of the ²³⁸U and ²³²Th results obtained by the INAA absolute method shows an acceptable level of consistency with those obtained by the INAA relative method.     

Comparison of relative INAA and k 0-INAA using soil and sediment reference materials

The objective of this work was to compare the results obtained by the relative INAA and k ₀-INAA methods for the same input parameters (sample mass, nuclear data, net peak area for the same gamma line and the same measurement and same cooling and measurement times). In total eight environmental soil and sediment reference materials (RM) or certified reference materials (CRM) from different producers were analysed. In this work only the recommended or certified values were considered, allowing comparison of the two methods for 30 elements. The results point out that k ₀-INAA possesses superior qualities compared to relative INAA, being insensitive to flux gradients, and independent of recommended/certified values in RMs/CRMs, often used as standards in relative INAA.     

Determination of vanadium in mussels by electrothermal atomic absorption spectrometry without chemical modifiers

A method was developed for the quantitative determination of total vanadium concentration in mussels via electrothermal atomic absorption spectrometry (ETAAS). After the microwave digestion of the samples, a program using temperatures of 1600 °C and 2600 °C for ashing and atomization respectively, without any matrix modifiers, allowed us to obtain results that were satisfactory since they agreed closely with certified reference material values. The detection limit was 0.03 mg kg^–1 (dry weight), indicating that the method is suitable for the analysis of mussel samples. This determination was compared with matrix modifiers that have been reported previously. The method was applied to various cultivated and wild mussels from the Galician coast, yielding levels below 1 mg kg^–1 (wet weight).     

Application of the INAA methods for KRISS infant formula CRM analysis: standardization of INAA at KRISS

We have established an instrumental neutron activation analysis (INAA) method, including k₀-based INAA, at the Korea Research Institute of Standards and Science (KRISS) for the certification of reference materials. As part of establishing INAA measurements, KRISS infant formula certified reference material was analysed for multiple elements at three different metrological institutes: KRISS and NIST for the standard comparator method, and JSI for the k₀-INAA method. The mass fraction of most elements was consistent within expanded uncertainty (k?=?2). In addition, the results were used to verify the validity of elemental analysis of Zn using the standard comparator INAA at KRISS, and spreadsheet-based INAA calculations were evaluated.

     

Application of INAA complementary gamma ray photopeaks to the homogeneity study of a mussel candidate reference material

Homogeneity study is one of the steps in reference material, RM, characterization. Due to its inherent characteristics, Instrumental Neutron Activation Analysis, INAA, is an analytical technique of choice for homogeneity testing. An interesting possibility is the use of complementary gamma ray photopeaks to confirm INAA homogeneity test results. In this study, the use of the complementary gamma ray photopeaks of ^110mAg, ⁸²Br, ⁶⁰Co, ¹³⁴Cs, ¹⁵²Eu, ⁵⁹Fe, ¹⁴⁰La, ²³³Pa (for Th determination), ⁴⁶Sc and ⁷⁵Se radionuclides was investigated in the between bottle homogeneity study of a mussel candidate RM under preparation at IPEN–CNEN/SP. Although some photopeaks led to biased element content results, the use of complementary gamma ray photopeaks proved to be helpful in supporting homogeneity study conclusions for the new RM under characterization.     

Development of reference materials for paralytic shellfish poisoning toxins

A project was undertaken to develop mussel reference materials that were certified for their mass fractions of saxitoxin and decarbamoyl-saxitoxin. Fifteen laboratories from various European countries participated. Three of these had major responsibility for substantial parts of the work and overall coordination of the project. The project involved 4 main activities: (1) procurement and characterization of calibrants; (2) improvement of analytical methodology; (3) preparation of reference materials, including homogeneity and stability studies; (4) 2 interlaboratory studies and a certification exercise. The joint activities resulted in 3 homogeneous and stable reference materials: 2 lyophilized mussel materials with and without naturally incurred paralytic shellfish poisoning (PSP) toxins, and a saxitoxin enrichment solution. The reference materials were certified with respect to their saxitoxin and decarbamoyl-saxitoxin content. The lyophilized mussel material with PSP toxins (CRM 542) contained <0.07 mg saxitoxin x 2HCl/kg and 1.59 +/- 0.20 mg decarbamoyl-saxitoxin x 2HCl/kg. The lyophilized mussel material without PSP toxins (CRM 543) contained <0.07 mg saxitoxin x 2HCl/kg and <0.04 mg decarbamoyl-saxitoxin x 2HCl/kg. The certified value of the saxitoxin mass fraction in the saxitoxin enrichment solution (CRM 663) was 9.8 +/- 1.2 microg/g.     

Establishing a basis for nuclear archaeometry in Australia using the 20 MW OPAL research reactor

The k ₀-method of standardisation for instrumental neutron activation analysis (INAA) has been used at the OPAL research reactor to determine the elemental composition of three certified reference materials: coal fly ash (SRM 1633b), brick clay (SRM 679) and Montana soil (SRM 2711). Of the 41 certified elements in the three materials, 88 percent were within five percent of the certified values and all determinations were within 15 percent of the certified values. The average difference between the measured and certified values was 0.1 percent, with a standard deviation of 4.1 percent. Since these reference materials are widely used as standards in the analysis of archaeological ceramics by INAA, it has been concluded that the INAA facility in Australia is particularly well-suited for nuclear archaeometry.     

Further investigating the determination of phosphorus in plants by INAA using<Emphasis Type="Italic"> bremsstrahlung</Emphasis> measurement

Phosphorus is an essential element for plants and animals, playing a fundamental role in the production of biochemical energy. Despite its relevance, phosphorus is not commonly determined by instrumental neutron activation analysis (INAA), because ³²P does not emit gamma-rays in its decay. There are alternative methods for the determination of phosphorus by INAA, such as the use of beta counting or the measurement of bremsstrahlung originated from the high energy beta particle from ³²P. Here the determination of phosphorus in plant materials by measuring the bremsstrahlung production was further investigated, to optimize an analytical protocol for minimizing interferences and overcoming the poor specificity. Eight certified reference materials of plant matrices with phosphorus ranging between 171 and 5,180 mg kg⁻¹ were irradiated at a thermal neutron flux of 9.5 × 10¹² cm⁻² s⁻¹ and measured with a HPGe detector at decay times varying from 7 to 60 days. Phosphorus solutions added to a certified reference material at three levels were used for calibration. Counts accumulated in the baseline at four different regions of the gamma-ray spectra were tested for the determination of phosphorus, with better results for the 100 keV region. The Compton scattering contribution in the selected range was discounted using an experimental peak-to-Compton factor and the net areas of all peaks in the spectra with energies higher than 218 keV, i.e. Compton edge above 100 keV. Amongst the interferences investigated, the production of ³²P from sulfur, and the contribution of Compton scattering should be considered for producing good results.     

Creatinine determination in urine from the point of view of reference values

In this paper, the creation of a certified reference material for urinary creatinine is described. We used the Jaffe method and HPLC method for establishment of the certified value. Homogeneity tests are also described. We obtained material with sufficient homogeneity, stability, and with certified value (expanded uncertainty, k=2 for CI 95%) (7.77±0.27) mmol·L⁻¹. This material was consequently used for the interlaboratory comparison (EQA Czech Republic for clinical chemistry). Twenty-nine percent of the participants obtained measurement results within the interval of the certified value ± expanded uncertainty, while 85% of the participants obtained values inside the interval of the certified value ± target measurement uncertainty. Direct use of the certified reference materials for method evaluation in EQA programs means a significant advance for monitoring and documentation traceability of results in routine measurements.     

Determination of concentrations of U and Th in their mixed oxides by INAA methods

Uranium and thorium mixed oxides are being prepared using natural U and Th for studies on fuels for Advanced Heavy Water Reactors, wherein composition of U and Th is specific and requires strict control in terms their contents and homogeneity. Chemical quality control necessitates accurate and precise compositional characterization of the fuel material by a suitable analytical method. Among various analytical methods for U and Th, instrumental neutron activation analysis (INAA) is one of the best methods for their simultaneous determination without chemical dissolution and separation. INAA methods using reactor neutrons namely thermal NAA and epithermal NAA were standardized for the determination of U and Th in their mixed oxides. Standards, synthetic samples and U–Th mixed oxide samples, prepared in cellulose matrix, were irradiated at pneumatic carrier facility of Dhruva reactor as well as at self serve facility of CIRUS reactor under cadmium cover (0.5 mm). Radioactive assay was carried out using a 40% relative efficiency HPGe detector. Both activation and daughter products of ²³⁸U (²³⁹U and ²³⁹Np) and ²³²Th (²³³Th and ²³³Pa) were used for their concentration determination. The method was validated by analyzing synthetic samples of 6–48%U–Th mixed oxides. The standardized method was used for the concentration determination of U and Th in 4–30%U–Th mixed oxide samples. Results of U and Th concentrations including associated uncertainties obtained from the INAA methods are presented in this paper.     

Vanadium biomonitoring by using <Emphasis Type="Italic">Perna perna</Emphasis> (Linnaeus, 1758) mussels transplanted in the coast of the State of São Paulo,Brazil

The increased pollution in the aquatic ecosystem has led to the investigation of toxic elements in sea water by using marine organisms to assess marine pollution from human activities. Among these organisms, the mollusks bivalves have been used as biomonitors since they can accumulate trace elements and other substances, without the occurrence of their death. In this study, Perna perna mussels were transplanted from a mussel farm (reference region) to four sites located in coastal regions of São Paulo State, Brazil, close to anthropic discharge areas. Vanadium was determined in mussel tissues by instrumental neutron activation analysis (INAA). Quality control of V analysis was checked by analyzing biological reference materials and the results obtained were precise and in good agreement with the certified values. Comparisons between the V concentrations obtained in transplanted mussels indicated that those from São Sebastião region, close to an oil terminal presented the highest concentration of this element, during spring.     

Certification of the mass fractions of Pt, Pd and Rh in a used car catalyst reference material

The high economic value of catalysts containing the platinum group elements platinum, rhodium and palladium as active components causes the need to be able to measure the precious metal loading with small uncertainty and to have suitable certified reference materials fulfilling high demands on the quality of the certified values. In European Reference Material ERM^®-EB504, a used cordierite-based car catalyst material, mass fractions of platinum, palladium and rhodium were certified. The raw material was milled, homogenised and annealed before analysis. Seventeen laboratories experienced in precious metals analysis participated in the certification interlaboratory comparison, most of them analysing with inductively coupled plasma optical emission spectrometry using different sample pretreatment techniques. Homogeneity testing was carried out using X-ray fluorescence spectrometry. The certified mass fractions of Pt, Pd and Rh and their expanded uncertainties (k = 2) in ERM^®-EB504 are (1777 ± 15), (279 ± 6) and (338 ± 4) mg/kg respectively.     

Comparison of Different Analytical Techniques for the Determination of Organic Mercury

Abstract

Methods for the determination of (1) total organic mercury (Hg) using an extraction +neutron activation analysis, (2) the sum of methyl-Hg+phenyl-Hg using ¹³¹I^?-Cl^? exchange and (3) methyl-Hg using two different Westöö modifications, have been compared. Sample materials were 8 falcon livers, 5 pike livers and 2 pike muscles. Although differences were found between the methods, interaction effects caused by either sample inhomogeneity or bad performance of the analytical methods impeded a clear interpretation of the comparison. Total Hg in the samples was determined by neutron activation analysis (NAA) and atomic absorption spectrometry. The accuracy of the total Hg determination using NAA was verified by the analysis of certified reference material.

In addition to the other organic Hg determinations phenyl-Hg was determined separately in some of the samples by an isotope exchange method using ²⁰³Hg²⁺.

The main conclusion of the study was that there is a demand for reference materials certified for at least total organic Hg and methyl-Hg.     

Determination of 22 elements in geological samples by instrumental neutron activation analysis

An instrumental neutron activation analysis (INAA) method has been developed for multi-element determination in geological samples. The INAA method consists of irradiation of samples for 90 sec at a flux of 1.0·10¹² n·cm⁻²·sec⁻¹ and determination of 12 elements by using their short-lived nuclides. Samples have been re-irradiated for 3 hrs for measuring concentrations of another 10 elements. Precision and accuracy of the INAA method have been evaluated by analysing samples and USGS standard reference materials. Precision and accuracy are within±15% and ±10%, respectively.     

Simple mercury fractionation in biological samples by CV AAS following microwave-assisted acid digestion or TMAH pre-treatment

A simple and reliable method to determine total and inorganic mercury in biological certified reference material (CRM) by cold vapor atomic absorption spectrometry (CV AAS) is proposed. After the CRM treatment at room temperature with tetramethylammonium hydroxide (TMAH), inorganic mercury is determined by CV AAS. Total mercury is measured by the same technique, after sample acid digestion in a microwave oven. Organic mercury, basically methylmercury, is obtained by difference. In both procedures, the quartz tube is kept at room temperature. By means of analysis of the following reference materials: pig kidney, lobster hepatopancreas, dogfish liver and mussel tissue, it was clear that the difference between the total and inorganic mercury concentrations agrees with the methylmercury concentration. Only one calibration curve against aqueous standards in acidic medium was carried out for both procedures. The concentrations obtained by both procedures are in agreement with the certified values according to the t-test at a 95% confidence level. The relative standard deviations were lower than 3.0% for digested CRM and 6.0% for CRM treated with TMAH for most of the samples. The limits of detection in the samples were 0.02 µg g^− 1 and 0.04 µg g^− 1 for inorganic and total Hg, respectively, since the sample mass for total mercury was half of that for inorganic mercury determination. Simplicity and high efficiency without using chromatographic techniques are some of the qualities of the proposed method, being adequate for fractionation analysis of mercury in biological samples.     

Development and certification of a reference material for Fusarium mycotoxins in wheat flour

Deoxynivalenol (DON), nivalenol (NIV) and zearalenone (ZEN) are toxic secondary metabolites produced by several species of Fusarium fungi. These mycotoxins are often found together in a large variety of cereal-based foods, which are regulated by maximum content levels of DON and ZEN. To date, suitable certified reference materials (CRM) intended for quality control purposes are lacking for these Fusarium mycotoxins. In order to overcome this lack, the first CRM for the determination of DON, NIV and ZEN in naturally contaminated wheat flour (ERM®-BC600) was developed in the framework of a European Reference Materials (ERM®) project. This article describes and discusses the whole process of ERM®-BC600 development, including material preparation, homogeneity and stability studies, and an interlaboratory comparison study for certification. A total of 21 selected expert laboratories from different European countries with documented expertise in the field of mycotoxin analysis took part in the certification study using various gas and liquid chromatographic methods. The certified values and their corresponding expanded uncertainties (k?=?2) were assigned in full compliance with the requirements of ISO Guide 35 and are as follows: 102?±?11 μg?kg^?1 for DON, 1000?±?130 μg?kg^?1 for NIV and 90?±?8 μg?kg^?1 for ZEN.     

Accurate measurement of bromine contents in plastic samples by instrumental neutron activation analysis

Accurate measurements of bromine contents in plastic samples were made by the direct comparator instrumental neutron activation analysis (INAA). Individual factors affecting the measurements were comprehensively evaluated and compensated, including the volatility loss of bromine from standard comparators, the background bromine level in the filter papers used for preparation of the standard comparators, nuclear interference, γ-ray spectral interference and the variance among replicates of the samples. Uncertainty contributions from those factors were thoroughly evaluated and included in the uncertainty budgeting of the INAA measurement. ⁸¹Br was chosen as the target isotope, and the INAA measurements for bromine were experimentally confirmed to exhibit good linearity within a bromine content range of 10–170 μg. The established method has been applied to the analysis of eight plastic samples: four commercially available certified reference materials (CRMs) of polyethylene and polystyrene and four acrylonitrile butadiene styrene (ABS) samples prepared as the candidate reference materials (KRISS CRM 113-01-012, -013, -014 and -015). The bromine contents of the samples were calculated at three different γ-ray energies and compared, showing good agreement. The results of the four CRMs also showed good consistency with their certified values within the stated uncertainties. Finally, the bromine contents of the ABS samples were determined with expanded uncertainties (at a 95% level of confidence) between 2.5% and 5% in a bromine content range of 25–900 mg kg⁻¹.     

Evaluation of droplet digital PCR for characterizing plasmid reference material used for quantifying ammonia oxidizers and denitrifiers

DNA reference materials of certified value have a critical function in many analytical processes of DNA measurement. Quantification of amoA genes in ammonia oxidizing bacteria (AOB) and archaea (AOA), and of nirS and nosZ genes in the denitrifiers is very important for determining their distribution and abundance in the natural environment. A plasmid reference material containing nirS, nosZ, amoA-AOB, and amoA-AOA is developed to provide a DNA standard with copy number concentration for ensuring comparability and reliability of quantification of these genes. Droplet digital PCR (ddPCR) was evaluated for characterization of the plasmid reference material. The result revealed that restriction endonuclease digestion of plasmids can improve amplification efficiency and minimize the measurement bias of ddPCR. Compared with the conformation of the plasmid, the size of the DNA fragment containing the target sequence and the location of the restriction site relative to the target sequence are not significant factors affecting plasmid quantification by ddPCR. Liquid chromatography–isotope dilution mass spectrometry (LC–IDMS) was used to provide independent data for quantifying the plasmid reference material. The copy number concentration of the digested plasmid determined by ddPCR agreed well with that determined by LC–IDMS, improving both the accuracy and reliability of the plasmid reference material. The reference value, with its expanded uncertainty (k?=?2), of the plasmid reference material was determined to be (5.19?±?0.41)?×?10⁹ copies μL^?1 by averaging the results of two independent measurements. Consideration of the factors revealed in this study can improve the reliability and accuracy of ddPCR; thus, this method has the potential to accurately quantify DNA reference materials.     

Determination of selenium species in plant leaves by HPLC-UV-HG-AFS

The purpose of this work was the development of a method for the determination of Se compounds in leaves of plants. Water-soluble Se compounds were extracted from samples by water. Enzymatic hydrolysis with the non-specific enzyme protease XIV was used for the release of Se compounds bound to proteins. Separation of Se species was made by ion exchange chromatography, using an anion exchange column for Se^IV, Se^VI and selenomethionine (SeMet), and a cation exchange column for selenomethylselenocysteine (SeMeSeCys) and selenocystine (SeCys₂). Columns were connected “on line” to a hydride generation atomic fluorescence spectrometer (HG-AFS) using a UV lamp between the separation and detection system. The repeatability of the results obtained by the developed method was under 15% (R.S.D.) for all Se species; the detection limit was 2-10 ng Se/g of supernatant. The accuracy was checked by comparison with some literature data for reference materials since there were no suitable certified reference materials available. The method was used for the determination of Se compounds in chicory (Cichorium intybus L.) leaves from plants which were cultivated aeroponically with elevated concentrations of Na₂SeO₄ for different periods. Se accumulated efficiently in chicory leaves; up to 480 μg/g after 41 days of exposure, mostly (64%) as Se^VI, i.e. in the form of Se added. Beside inorganic Se, in the extracts from enzyme hydrolysis we also found SeMet (4.2-8.4%) and SeMeSeCys (<DL−0.7%). Some unidentified peaks were also observed in the chromatograms of plant extracts.     

The performance of k0-INAA in recent exercises on the certification of rare earth elements in bio-environmental materials

The performance of k ₀-INAA was studied for the determination of the rare earth elements (plus Th and U) in the certification of four new BCR CRM's: 667 Estuarine Sediment, 690 Calcareous Soil, 670 Aquatic Plant and 668 Mussel Tissue. Our results are critically compared with the (later on) certified values, revealing slight discrepancies for the organic matrices aquatic plant and mussel tissue. Although these discrepancies were thought to be associated with the special procedure followed for moisture content determination, no convincing explanation could be found. Mention is also made of problems that are affecting the accuracy and precision of our results, especially with respect to multiplet deconvolution or otherwise troublesome peak fitting, spectral interferences, reaction interferences (notably from ²³⁵U-fission) and the non-1/v thermal cross section behavior. Eventually, detection limits for the REEs (+ Th and U) are calculated in the four materials, allowing to evaluate the applicability of INAA to these types of bio-environmental matrices. This revised version was published online in August 2006 with corrections to the Cover Date.