Evaluation of INAA-anticoincidence counting for measuring nanogram levels of vanadium in relatively high-salt nutritional reference materials

An instrumental neutron activation analysis method in conjunction with anticoincidence counting (INAA-AC) gamma-ray spectrometry was developed for the determination of ppb levels of V in biological, mostly nutritional, reference materials containing varying amounts of salt. The method involved irradiation in the Dalhousie University SLOWPOKE-2 reactor facility at a fission neutron flux of 5 × 1011 cm-2 s-1 for 1 min, decay for 1 min, and counting for 10 min. In order to fully investigate the extent of improvement that can possibly be obtained for V determination by INAA–AC, a theoretical term called the analytical figure of merit was developed and applied to 16 National Institute of Standards and Technology and International Atomic Energy Agency reference materials. The overall background around the 1,434.1-keV photopeak of 52V was reduced by a factor of 5-10 for several materials in the anticoincidence counting mode. The detection limits were lowered by factors of 3-5 in INAA-AC (0.61-9.4 μg kg-1) compared to conventional INAA (1.9-79 μg kg-1) in samples with varying ratios of Na/V (0.24-1,000), Cl/V (0.12-1,827), Al/V (7.45-115) and Mn/V (1.84-66.9) making rapid and reliable V measurements possible at sub-ppb levels without any chemical separation. (author)