An investigation of quenching effects in the direct fluorimetric determination of uranium in minerals

Determination of Uranium in Biological Materials by Laser Fluorimetry

“…Because of the relatively simple equipment required and the low detection limit (ng region) the method was widely used in the detection and determination of uranium in nature. Its most serious drawback, the quenching of the uranium fluorescence by many interfering Clements, could be overcome by various techniques such as dilution, addition of an internal Standard or the Separation of the element from its matrix (for details see [30][31][32][33][34][35]). In addition to this, fusion of the (processed) samples with certain very pure chemicals such as alkali carbonates and alkali fluorides (or mixtures of them) in platinum (sometimes also gold) dishes is required.…”

Basic Considerations Concerning the Behaviour of Quenchers in the Fluorimetric Determination of Uranium

“…by the presence of various elements has been investigated repeatedly, theoretically [1] as well as practically [2 -10]. The interfering effect of the quencher can be evaluated and corrected for by the addition of an internal uranium Standard ("spike") as long as the fluorscence reduction does not exceed about 60%; for details concerning the possibilities to overcome the negative influence of quenching on the results of fluorimetric uranium analysis see [5,6].…”

“…It was found [6], that the quenching effect of an element obeys a semilogarithmic function of the quencher concentration in the flux pellet in analogy to LAMBERT'S law (see also [12]), the same is valid for mixtures of quenchers as long as the ratios of the individual quenchers remain unaltered. This makes possible a Classification of the "quenching power" of the corresponding elements, which is based on the numerical values of their "halfconcentrations" (cj 12), e. g. that concentration of the quencher in the flux, which reduces the initial (unquenched) uranium fluorescence by 50%.…”

“…This makes possible a Classification of the "quenching power" of the corresponding elements, which is based on the numerical values of their "halfconcentrations" (cj 12), e. g. that concentration of the quencher in the flux, which reduces the initial (unquenched) uranium fluorescence by 50%. A new "direct" determination of uranium in minerals without any chemical pretreatment of the sample can be performed by a simple extrapolation of the quenching function (for details see [6]). …”

“…The experimental techniques required for the determination of half-concentrations of various elements and the fluorescence of mixtures are described in detail in [6]. A GALVANEK-MORRISON fluorimeter of the Jarrell-Ash Div.…”