Comparator Element:

In order to achieve better accuracy and to eliminate errors due to secondary standard, a Monostandard (ko) Method has been proposed. In this method a single element such as Au, Mn, Co with 100% isotopic abundance is used as a comparator for multielement NAA. Various schemes have been devised to accomplish this and the most significant of these is k_o method. Subsequent equation is used to calculate the concentration (w) using this method.

w (µg / g) =(Asp/A*sp)(1/K_o ) (f  + Q*₀ (α ))ε */( f  + Q*₀ (α ))ε

where A_sp is the exact activity, f is the thermal to epithermal flux ratio

Q₀ is the ratio of the resonance integral to the thermal neutron cross section;

ε is the detector effectiveness; α is the deviation of the epithermal flux from ideality

k₀ = the k₀ factor (M i * γ * σ th / M i * γ * σ *th); *corresponds to the comparator element

The k_o factor is an experimentally determined value that contains the values for the nuclear constants needed in the activation analysis. In Eq. 13.13 a new term K_anal  is introduced so that it may now be written as

ρ(µg/g ) =      A'p P/A*_sp. 1/K_anal where K_anal =k_o (f+Q_o)/(f+Q_o)*. ε/ ε*

where A′p  is the peak area of the ith element corrected for saturation, cooling and decay during counting and normalized for 1 g sample. The k_o factors for many nuclides have been determined and published using gold as a comparator element.