Spectral Interferences:

Gamma-ray spectral interferences occur when similar γ-ray energies are produced by other radionuclides produced by other elements. For example: 846.8 keV of ⁵⁶Mn is often interfered by 844 keV of ²⁷Mg. Similarly 279.2 keV of ²⁰³Hg is interfered with 279.5 keV of ⁷⁶Se. In such cases other indicator gamma rays should be used or one should wait for the decay of the other radio nuclide. For example, ⁵⁶Mn has t _½ =155 min. and it should be counted after an hour so that ²⁷Mg (t _1/2= 9.45 min) may undergo decay during this period.

Other types of less common interferences are due to successive capture and secondary particles from primary reaction. For instance, in the determination of manganese through (n, γ) reaction producing ⁵⁶Mn is also produced through a successive reaction, ⁵⁴Cr (n, γ) ⁵⁵Cr β- , ⁵⁵Mn (n, γ) ⁵⁶Mn. Similarly while determining nitrogen in proteins via ¹⁴N (n, 2n) ¹³N and ¹³C (p, n) ¹³N.