Low-level determination of silicon in biological materials using radiochemical neutron activation analysis

A new radiochemical neutron activation analysis (RNAA) method has been developed for low-level determination of Si in biological materials, which is based on the Si-30(n,gamma)Si-31 nuclear reaction with thermal neutrons. The radiochemical separation consists of an alkaline-oxidative decomposition followed by distillation of SiF4. Nuclear interferences, namely that of the P-31(n,p)Si-31 with fast neutrons, have been examined and found negligible only when irradiation is carried out in an extremely well-thermalized neutron spectrum, such as available at the NIST reactor. The RNAA procedure yields excellent radiochemical purity of the separated fractions, which allows the measurement of the beta(-)-activity of the Si-31 by liquid scintillation counting. Results for several reference materials, namely Bowen's Kale, Bovine Liver (NIST SRM 1577b), Non-Fat Milk Powder (NIST SRM 1549) and several intercomparison samples, Pork Liver-1, Pork Liver-2 and Cellulose Avicel, are presented and compared with literature values.