A generalized separation reaction scheme for assessment of the radioanalytical method of concentration dependent distribution

Abstract

For the assessment of the analytical error of concentration dependent distribution (CDD), complex-forming separation reaction was proposed in a generalized form of equilibrium\(ML_{ } + + nL \rightleftarrows \overline {ML} _{ }\), where n is the effective stoichiometric coefficient, i.e. the difference of mean ligand numbers\( \) and of a mixture of complexes of analyte M with reagent L in the respective groups (distinguished by bars above the symbols) of the separation system. Calibration curve\(I = A/\bar A\) is derived from measurement of gross activity of complexes, A=A(ML ) and\(\bar A = A(\overline {ML} _{ } )\). Theoretical relative error is expressed as a product of three terms, δx/x=f1f2f3. The first term f1 depends on the degree of isotopic dilution, and the recommended ratio of amounts of nonradioactive (x) and radioactive (y) substance M is x/y∈(1;4). The second term f2 depends first of all on the slope of distribution ratio (yield of separation\(\bar R\)) vs. the analyte; reagent ratio, n(Z+1)/T. The form of slope is analyzed on the basis of the generalized separation reaction. Optimal conditions were discussed from this point of view and the ideal case is at f2=1. The third term f3 depends on the activities A and Ā, i.e. on the distribution ratio, sample volumes, and the manner of counting. The ideal ratio of sample activities is A=Ā and the optimal interval\(\bar R\) ∈ (0.2;0.8) is suggested