Selenium content of Argentinean infant formulae and baby foods by pseudo-cyclic instrumental neutron activation analysis coupled to Compton suppression

The selenium levels of Argentinean infant formulae and baby food were measured using the 162-keV gamma-ray of 77mSe (t½ = 17.4 s) by a pseudo-cyclic instrumental neutron activation analysis (PC-INAA) method in conjunction with Compton suppression spectrometry (CSS). For comparison purposes, 5 selected infant formulae were also analyzed for selenium by a radiochemical neutron activation analysis (RNAA) method. The selenium levels for three samples agreed between ±2.8 and 6.5 % while the other two differed by 12 and 17 % which could perhaps be attributed to sample inhomogeneity. The selenium content of cow milk-based infant formulae varied from 42-146 μg kg-1 compared to 52-63 μg kg-1 for soy-based milk formulae. In the case of baby foods, the selenium levels varied from 34 to 74 μg kg-1. The detection limits for selenium by PC-INAA-CSS for all the samples analyzed in this work were between 8.5 and 65 μg kg-1 depending on the major elements present in the samples, while it was 20 μg kg-1 for the RNAA method. The expanded uncertainty (κ = 2) of the PC-INAA-CSS method was 7.0 % at the end of cycle 4 for a sample containing 73.7 μg kg-1 selenium compared to the RNAA value of 24.2 % for a sample of 67.0 μg kg-1 selenium content. (author)