Neutron capture prompt-gamma activation analysis of foods.

The suitability of neutron capture prompt-gamma activation analysis (PGAA) for multielement analysis of foods was investigated. A total of 22 elements was observed in 40 food and mineral supplements. Hydrogen, B, C, N, Na, S, Cl, and K concentrations were determined in NIST RM 8431a Mixed Diet and in a wet diet composite made from FDA Total Diet Study collections. Because the neutron flux is so low for PGAA, the method is nondestructive and reanalysis of analytical portions is possible. Both diet materials were analyzed before and after freeze-drying to check for element losses during this process. No losses were found for RM 8431a, but significant losses of B and Na were observed for the wet composite. The measured loss of hydrogen for the wet composite was not consistent with the assumption that the lost mass was water only.