Analytical problems related to the preparation of samples used in studies on metallobiochemistry of heavy metals pollution using neutron activation analysis

Severe analytical problems are associated with the analysis of heavy metals at very low levels in biological samples. This impose a high degree of sophistication of the NAA involving treatment of the sample before irradiation such as chemical separations, physical treatments and biochemical fractionation, the experimental evaluation of interfering nuclear reaction as well as the development of post-irradiation radiochemical separation. This paper treats of the problem related to the NAA of trace elements in environmental biochemical toxicology focussing attention of the sources of the elements during the analysis. Typical results and short discussion for every step of the analysis are reported.     

Comparative analysis of ancient ceramics by neutron activation analysis,inductively coupled plasma-optical-emission spectrometry,inductively coupled plasma-mass spectrometry,and X-ray fluorescence

The accurate measurement of the maximum possible number of elements in ancient ceramic samples is the main requirement in provenance studies. For this reason neutron activation analysis (NAA) and X-ray fluorescence (XRF) have been successfully used for most of the studies. In this work the analytical performance of inductively coupled plasma-optical-emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) has been compared with that of XRF and NAA for the chemical characterization of archaeological pottery. Correlation coefficients between ICP techniques and XRF or NAA data were generally better than 0.90. The reproducibility of data calculated on a sample prepared and analysed independently ten times was approximately 5% for most of the elements. Results from the ICP techniques were finally evaluated for their capacity to identify the same compositional pottery groups as results from XRF and NAA analysis, by use of multivariate statistics.     

Selective removal of radio-sodium from neutron-activated materials by retention on hydrated antimony pentoxide

A new method is presented to remove sodium interferences from neutron-activated materials. The method is based on passage of the samples, dissolved in a concentrated acid solution on a column of hydrated antimony pentoxide (HAP). The retention is quantitative with a maximum capacity of 31 mg Na/g HAP. Only tantalum, in addition to sodium, was retained by HAP out of the 60 elements tested. The method should find applications in neutron activation analysis, particularly of biological materials. Applications are also foreseen in other analytical techniques, such as emission spectroscopy and flame spectrophotometry, where high sodium concentrations in the sample can be a source of interference.     

Comparison of NAA and ICP-MS for the determination of major and trace elements in environmental sample

Summary Major and trace elements in soil and plant samples, including standard reference materials were determined by means of neutron activation analysis (NAA) and inductively coupled plasma-mass spectrometry (ICP-MS). The analytical procedure for NAA utilized dried powder samples. The concentration of iodine in soil samples was determined by radiochemical NAA. The irradiated samples were cooled and then counted with a Ge gamma-ray detector connected to a multi-channel analyzer. For ICP-MS analysis, the samples were decomposed by microwave digestion with an acid mixture. The concentration of I in the soil samples was measured by ICP-MS after separation by ignition. The analytical values for most elements in the environmental samples by both methods were in good agreement, whereas sample treatments were different. Measured value of Zr in the soil samples by ICP-MS was about 50% lower than that by NAA. It should be assumed that some minerals of Zr in soil particles were not entirely dissolved by the acid mixture. Analytical results of Cd for three different Cd levels in unpolished rice flour samples (NIES 10-a, b and c) determined by ICP-MS were in agreement with certified values. The concentration of Cd in the sample with the lowest Cd level, as determined by NAA with 57% counting error, was 3 times higher than the certified value.     

Neutron activation analysis investigations in updating REE composition of gabbro GOG-1 reference sample: A comparison with SIMS and ICP-AES data

An updata REE measurement of gabbro GOG-1 was carried out by means of neutron activation analysis (NAA). The availability of high amounts of rock powder allowed the sample to be well ground and homogenized before analysis. Homogeneity tests, carried out on different aliquots, show that GOG-1 samples can be considered homogeneous when over 50 mg aliquots of rock powder are employed for analytical work. Results from ICP-AES and SIMS investigations of REE in gabbro GOG-1 are in quite good agreement with NAA data and support the possibility of employing GOG-1 rock samples as reference material for geoanalysis.     

New Developments in Activation Analysis for Material and Environmental Sciences

Activation analysis in general and mainly reactor neutron activation analysis (NAA) has been used extensively for measuring trace elements in high purity materials, particularly semiconductor materials. The advantages of NAA in determination of trace elements differ from one semiconductor material to another. For all of them the inherent properties of activation analysis especially those of non contamination with the reagents, low blanks and high sensitivity are the reasons for the choice of NAA as the main analytical procedure. These inherent properties are essential for analysis of high-purity materials where concentrations of ppb's and sub ppb's have to be measured. NAA is specially suitable for the determination of trace elements in silicon due to the very short lived very low activity induced by neutron reaction in silicon. This enables easy instrumental (i.e. without chemical separations) determination of trace elements in silicon. In the HFR reactor at Peten, Netherlands, a special facility was constructed for irradiation of silicon samples of Philips, in which silicon wafers of up to 15 cm diameter can be irradiated with 4 × 10¹³n. cm^?2. sec^?1 and the irradiation is done for 72–96 hours. using large Ge(Li) detectors (100 to 150cc) and long counting time (8–16 hours) they measured 22 elements in concentrations below ppb and 10 others between ppb and 300 ppm. Trace elements in germanium have been determined both instrumentally after very long decay time (100 days) or after short decay time removing the activities from the matrix by chemical separation. Trace elements in GaAs are determined only after chemical separtion. Several other semiconductor material such as Sc, Te, GaP and CuInS₂ were also determined by NAA. Some trace elements cannot be determined by neutron activation. Carbon, nitrogen and oxygen are determined by activation with protons, alphas or ³He particles. Boron and hydrogen are determined by prompt emission induced by charged particle activation, which gives not only the total concentration but also the depth profile. Carbon, nitrogen, oxygen and phosphorus were also determined by prompt proton activation analysis. The environmental samples studied by activation analysis can be divided into three categories: atmospheric aerosols, water samples and solid wastes. NAA of atmospheric aerosols have been used for their posible toxicological hazards, their source identification and for studies of atmospheric transport processes.     

Neutron activation analysis of bulk samples from Chinese ancient porcelain to provenance research

Neutron activation analysis (NAA) is an important technique to determine the provenance of ancient ceramics. The most common technique used for preparing ancient samples for NAA is to grind them into a powder and then encapsulate them before neutron irradiation. Unfortunately, ceramic materials are typically very hard making it a challenge to grind them into a powder. In this study we utilize bulk porcelain samples cut from ancient shards. The bulk samples are irradiated by neutrons alongside samples that have been conventionally ground into a powder. The NAA for both the bulk samples and powders are compared and shown to provide equivalent information regarding their chemical composition. Also, the multivariate statistical have been employed to the analysis data for check the consistency. The findings suggest that NAA results are less dependent on the state of the porcelain sample, and thus bulk samples cut from shards may be used to effectively determine their provenance.     

Systematic separation and determination of some neutron-activated nuclides and actinides in fallout samples

A method for systematic separation and determination of some neutron-activated nuclides and actinides is described. The method is designed to utilize stable isotopes and radioactive tracers as chemical yield monitors and to separate nuclides of interest from a single limited sample. Gravimetric, spectrophotometric, radiometric and X-ray fluorescence analysis were used for determination of chemical yields of the nuclides. Overall chemical yields generally ranged from 60–90%. Separated and purified nuclides were detected by -spectrometry or isotope dilution -spectrometry. The detection limit for neutron-activated nuclides is 10⁷ nuclides and the precision is better than 3% RSD.     

Development and applications of <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript> based NAA and prompt gamma-ray NAA methods at BARC

A summary of k ₀-based R&D work on neutron activation analysis (NAA), internal mono standard NAA (IM-NAA) and prompt gamma-ray NAA (PGNAA) is presented. The k ₀-based NAA was standardized by characterizing irradiation sites of research reactors, validated using reference materials and applied to samples of different origin. Recently IM-NAA method was developed, validated for small and large size samples and applied for the analysis of large size as well as non-standard geometry samples. Studies on PGNAA included characterization of neutron beam, determinations of detection efficiency and prompt k ₀-factors, and analytical applications.     

Comparative study of activation analyses for the determination of trace halogens in geological and cosmochemical samples.

Halogens (fluorine, chlorine, bromine and iodine) were determined by activation analyses (neutron activation analysis (NAA), photon activation analysis (PAA) and prompt gamma-ray analysis (PGA)) for geological and cosmochemical solid samples. We studied how each analytical method was for the determination of trace amounts of halogens in rock samples. Radiochemical NAA (RNAA) showed the highest analytical reliability for three halogens (chlorine, bromine and iodine), whereas a set of four halogens (fluorine, chlorine, bromine and iodine) could be determined in principle by radiochemical PAA (RPAA) from a single specimen. Although it is a non-destructive method, PGA showed an analytical sensitivity for chlorine comparable to those of RNAA and RPAA.     

Activation analysis: The most important method for control of purity of semiconductor silicon

NAA and CPAA are the most sensitive analytical tools for the determination of residual impurities in semiconductor silicon. Extremely small detection limits are found by measuring the activity in an underground laboratory. The accuracy and reliability of the methods were checked by several comparisons: interlaboratory comparison on NAA, another CPAA with IR-spectrometry as well as comparison of NAA-results, obtained instrumentally and by chemical separation.     

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.     

Neutron activation analysis applications at the Savannah River Site using an isotopic neutron source

NAA using ²⁵²Cf is used to address important areas of applied interest of the Savanah River Site (SRS). Sensitivity needs for many of the applications are not severe; analyses are accomplished using a 21 mg ²⁵²Cf NAA facility. Because NAA allows analysis of bulk samples, it offers strong advantages for samples in difficult-to-digest matrices when its sensitivity is sufficient. Following radiochemical separation with stable carrier addition, chemical yields for a number of methods are determined by neutron activation of the stable carrier. In some of the cases where no suitable stable carriers exist, the source has been used to generate radioactive tracers to yield separations.     

WDXRF, EPMA and SEM/EDX Quantitative Chemical Analyses of Small Glass Samples

Quantitative chemical analysis is a powerful tool for the classification and discrimination of small glass fragments in forensic and archaeometric analytical issues. In the choice of the analytical method the small dimensions and the irregular shape of the fragments must be accounted for. Several accurate and highly sensitive instrumental techniques successfully employed for the chemical analysis of small glass samples (AAS, ICP-AES and FAAS) are destructive, and therefore unacceptable for these applications. X-ray analytical techniques such as WDXRF, EPMA and SEM/EDX provide means for rapid, non destructive and sensitive multi-elemental analysis of glass fragments. In this study the analytical sensitivity and accuracy of WDXRF, EPMA and SEM/EDX for the analysis of small commercial glass fragments are investigated. The results are compared and discussed in order to establish a relation between the minimum size of glass samples and the accuracy and sensitivity of the analytical methods.     

Determination of iodine in diverse botanical and dietary matrices by pre-irradiation combustion followed by neutron activation analysis

Summary The method chosen for determination of iodine in this investigation is an extension of an existing analytical technique to food samples which was developed for environmental samples. The method is based on pre-irradiation combustion of the sample to liberate iodine, trapping the iodine on charcoal, and quantitating the element by neutron activation analysis (NAA). Existing botanical and dietary reference materials were used to check the validity of the method. Several mixed diet samples with high fat content from the U.S. Total Diet Study and composites of cereals with both low and high iodine content were analyzed. This method of pre-irradiation combustion followed by NAA has been shown to be a viable technique for the determination of iodine in dietary samples. However, with a detection limit of about 50 ng of iodine, large amounts of sample (>1 g) are typically required for each determination.     

Application of NAA to air particulate matter collected at thirteen sampling sites in eight Asian countries: A collaborative study

Air particulate matter (APM) samples (PM_2.5 and PM_10–2.5) were collected at 13 sampling points in 8 Asian countries and their chemical compositions were determined by using neutron activation analysis (NAA) with the k ₀-standardization method in addition to conventional comparative method of NAA. Analytical data showed that mass concentration and elemental composition of the APM collected are variable in terms of time and space, and are related to the characteristics of the sampling sites concerned. NAA was proved to be highly effective for the regional characterization of APM in chemical composition.     

Comparison of INAA and RNAA Methods with Thermal-Ionization Mass Spectrometry for Iridium Determinations in Atmospheric Tracer Studies

The sensitivity and precision of instrumental neutron activation analysis (NAA), radiochemical neutron activation analysis (RNAA), and thermal ionization mass spectrometry (TIMS) are compared for the determination of Ir in ambient size-fractionated aerosol particulate samples. The results of the TIMS analyses indicated high analytical precision (0.2% at >50 pg Ir), but the sensitivity of detection was limited by blank values (300–500 fg). The sensitivities for INAA and RNAA were comparable, i.e., 60 to 90 fg in size-segregated particulate samples.     

Simultaneous determination of Al,V, Mn and Cu from neutron-activated saline matrices by precipitation with poly-5-vinyl-8-hydroxyquinoline

Neutron Activation Analysis is a sensitive technique for the determination of more than seventy elements at the trace concentrations. The NAA analysis of biological and environmental matrices suffers from interferences caused by the presence of high concentrations of activated salts in these matrices. The high gamma-ray activities of these activated salts mask the low gamma-ray activities of short half-lived isotopes (e.g.,⁶⁶Cu,⁵⁶Mn,²⁸Al and⁵²V) necessitating the rapid separation of trace metals from high concentrations of salts. Poly-5-vinyl-8-hydroxyquinoline has been used to develop a new method to rapidly and quantitatively precipitate aluminum, copper, vanadium and manganese from neutron-activated biological and environmental matrices.     

Evaluation of heavy metal uptake in micropterus salmoides (Largemouth Bass) of Lake Austin,TX by neutron activation analysis

Neutron activation analysis was used to investigate and quantify the level of heavy metal uptake in the marine environment of Lake Austin in Austin, TX. Specifically, the samples studied were largemouth bass, or micropterus salmoides. The presence of heavy metals in the food chain presents multiple hazards, mostly as a food hazard for those species that ingest the fish, namely humans. To measure the concentrations of heavy metals in various fish samples, the nuclear analytical technique of neutron activation analysis (NAA) was used. Both epithermal and thermal irradiations were conducted for the NAA to look for short and long-lived radioisotopes, respectively. The samples themselves consisted of liver and tissue samples for each of the fish caught. Each sample was freeze-dried and homogenized before irradiation and spectrum acquisition. The results showed that all levels of heavy metals were not sufficient enough to make the fish unsafe for eating, with the highest levels being found for iron and zinc. Gold was found to be at much higher concentrations in the younger fish and virtually non-existent in the larger of the samples.