Uptake of oxygen in a coal standard reference material (R) determined by fast (14-MeV) neutron activation analysis

A fast (14-MeV) neutron activation analysis procedure was employed to direc tly measure mass fractions of oxygen in coal samples. The procedure demonst rated sufficient precision and accuracy to determine a relative change of a bout 5% or more, in the oxygen mass fraction of about 12%. The procedure wa s applied to test samples of the newly developed SRM 1632c Trace Elements i n Coal (Bituminous). The samples had been stored at three conditions: in li quid nitrogen vapor and at room temperature in the original containers pack aged under argon, and for accelerated aging at 50 degreesC open to air. Fol lowing six months storage increments, duplicate samples of each of twelve b ottles of the SRM were measured for each storage condition. In addition eac h sample was processed through ten separate analytical runs yielding a tota l of some 720 measurements per storage duration. Oxygen was determined by c omparison to a primary standard potassium dichromate and the accuracy of th e method was assessed through the analysis of replicate samples of three re ference materials that are certified for oxygen content. The initial 6-mont hs test period indicated uptake of oxygen in the open-air storage.