Interferences:

NAA is based on nuclear phenomenon and hence no chemical interferences are possible. Possible nuclear interferences are primary, secondary and second order interference reactions, gamma ray spectral interference, neutron self-shielding, γ-ray self-attenuation, true and random coincidences during gamma ray measurement. Some of these are described in following lines.

Primary Interferences:

It arises when the same radionuclide is formed from other than the analyte element. For example, in the case of ⁵⁶Mn produced by (n, γ) reaction, the same radionuclide is also produced by ⁵⁶Fe (n, p) and ⁵⁹Co (n, α) reactions on iron and cobalt respectively. Thus, determination of Mn in steel containing iron and cobalt may be erroneous if higher energy neutrons are present. If the sample is irradiated with thermal neutrons only or Cd/B shielding is used then these interfering reactions may be eliminated. Other examples of such interferences are in the determination of Al in presence of Si and P in soil or Na in presence of Al and Mg in biological samples.