Abstract
Mercury (Hg) is a toxic element released into the environment mainly by anthropic activities. Consequently, the improvement for Hg determination in environmental samples is of great interest. Instrumental Neutron Activation Analysis (INAA) is considered an adequate method to determine several elements. However, Hg determination by INAA is often hampered by its volatility, which causes losses. The aim of this study was to establish adequate irradiation conditions for Hg determination in environmental samples by INAA. The following parameters were evaluated: irradiation time, container for irradiation and spectral gamma ray interferences. For the study, aliquots of certified reference materials (CRMs) and tree bark samples were irradiated together with Hg synthetic standard at the IEA-R1 nuclear research reactor. Gamma ray activities of 197Hg and 203Hg were measured in a spectrometer coupled to a HGe detector. Obtained results indicated that polyethylene capsules or envelopes can be used as container for sample irradiation and the Hg impurities in these containers were negligible. Irradiation time of one hour was adequate for Hg determination and in long irradiations of 8 h problems of spectral interference of 198Au and 75Se were observed. In addition, Hg loss during the irradiation of 1 h and after irradiation was not observed. Quality control of Hg results, obtained in the CRMs analyses using one hour of irradiation, indicated good precision and accuracy with HORRAT < 2 and |Z score| < 2. The experimental conditions established in this study were applied to tree bark samples. Detection limits in these analyses were between 0.14 and 1.9 µg g-1.
Highlights
Mercury (Hg) is a toxic element that causes adverse effects on human health and on the environment, arousing much concern everywhere due to its volatility, persistence and bioaccumulation [1]
Certified reference materials For quality control in relation to the precision and accuracy of the results, certified reference materials (CRMs) INCT M-4 CormTis Cormorant Tissue provided by Institute of Nuclear Chemistry and Technology, IAEA-085 Methylmercury, Total Mercury and Other Trace Elements in Human Hair provided by International Atomic Energy Agency, NRC DOLT-3 Dogfish Liver Certified Reference Material for Trace Metals provided by National Research Council Canada and BCR 186 Trace Elements in Lyophilised Pig Kidney provided by Community Bureau of Reference were analyzed
By measuring 197Hg and 203Hg for different decay times, results of Hg mass fraction were obtained, and they varied from 23.23 ± 0.11 to 26.75 ± 0.40 μg g-1, for sample irradiated in polyethylene capsule, and from 23.58 ± 0.14 to 25.536 ± 0.087 μg g-1, when polyethylene envelope was used
Summary
Mercury (Hg) is a toxic element that causes adverse effects on human health and on the environment, arousing much concern everywhere due to its volatility, persistence and bioaccumulation [1]. Instrumental neutron activation analysis (INAA) is considered an advantageous technique for element determination of environmental contaminants, since it is a non-destructive technique, that requires minimal manipulation of the sample and provides low detection limits [4,5]. Some elements are not determined with good accuracy by this technique, as in the case of Hg. In the analysis of Hg by INAA, two radioisotopes that can be measured for its quantification are formed: 197Hg (77.34 keV with half-life of 64.16 h) and 203Hg (279.20 keV with half-life of 46.61 d) [6]. The aim of this study was to establish adequate conditions for Hg determination in environmental samples by INAA in IEA-R1 reactor. Environmental certified reference materials and tree bark samples, used as environmental biomonitor, were analyzed
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