B. Magyar, PROBLEMS INVOLVED IN THE CALCULATION OF THEORETICAL SENSITIVITIES OF FLAME ATOMIC-ABSORPTION MEASUREMENTS, Mikrochimica acta, 111(1-3), 1993, pp. 1-36
Theoretical sensitivities cannot replace calibration. Nevertheless, th
ey are important for standardless atomic absorption determinations, an
d especially, for optimization of experimental conditions. Starting wi
th fundamental processes involved in the interaction of electromagneti
c radiation with the matter, a simple sensitivity formula was derived.
S(A) = [dA(lambda(o))/dc(A)]o = K(n)(b/D)(rho/M(A))lambda(o)G The sen
sitivity S(A) is the initial slope of the calibration curve absorbance
A(lambda(o)) measured at the centre lambda(o) of the resonance line v
s. concentration c(A) of the element to be determined (analyte A). The
relative atomic mass M(A) of the analyte and the density rho of the s
olutions need no further discussion here. The ratio (b/D) of the absor
ption path length b to the dilution factor determines the sensitivity
of determinations by AAS to a high degree and will be discussed in det
ail. The numerical factor K(n) depends on the concentration unit and t
he system of units (CGS or SI) used for the physical constant involved
. The former were always used in earlier works in the field of atomic
spectroscopy. In order to make a connection more easily between classi
c (CGS) and modern (SI) formulations, the most important equations are
given in both systems of units. The other important factors are combi
ned in the group G-factors of dimension one. The comparison of the the
oretical and experimental sensitivities may be transformed to the comp
arison of theoretical and experimental G-values. Whereas the compariso
n of sensitivities is always limited to an experimental set-up, the co
mparison of G-values is released from this ''ballast'' and therefore w
ill be preferred here. It is proposed that experimental G-values are c
omputed from experimental sensitivities and used for compilations in t
he future, because they are more precise and accurate than their cofac
tors.