Speaker
Igor Izosimov
(Khlopin Radium Institute)
Description
A widespread application of tunable lasers to analytical problems gave impetus to development of new procedures for detection of trace amounts of a substance in various media. A capability to vary the wavelength of laser radiation allows selective action on atoms and molecules and also their selective detection. From the practical standpoint, liquids are the most suitable for analysis since atoms and molecules in liquids are in the area of interaction with laser radiation at all times. The analytical procedures based on laser spectroscopy as applied to liquids allow determination of valent states of the element and type of molecule [1].
Plutonium, neptunium and some uranium compounds do not exhibit direct luminescence in solutions and, hence, conventional procedure with time resolution (TR) of analytical luminescent signal (TRLIF) cannot be used for their detection in solutions. However, for detection of plutonium, neptunium and uranium the TR procedure can be used with registration of chemiluminescence of luminol (5-amino-1,2,3,4-tetrahydro-1,4-phthalazinedione), which arises under the action of OH radicals generated in solutions by light-excited actinide ions. We used this procedure for detection of actinides in solutions containing AnO2(2+) ions (An = U, Np, Pu) [2]. In this case, the chemiluminescence kinetics is characterized by burning up for three microseconds and decay of chemiluminescence with a characteristic time of approximately two microseconds.
Selective two-step excitation of actinyl-containing complexes by tunable lasers allows detection of actinide elements from the chemiluminescence of luminol.
For detection of small amounts of actinides it is necessary to exclude a possibility of registration of luminol luminescence having nature different from chemiluminescence. Therefore, we studied luminol luminescence in aqueous-alcoholic solutions with various water contents. It was found that with decreasing water content the intensity of luminescence having chemiluminescence nature decreases; in addition we observed a luminescence with red-shifted spectrum and kinetics having no burning-up stage typical for chemiluminescence. It should be noted that this luminescence different from chemiluminescence arises in single-quantum UV excitation of luminol molecule and can be significantly depressed in two-quantum excitation induced by radiation with longer wavelength since luminol has no absorption bands in visible region.
The results of the study allows conclusion that the presence of a burning-up stage with duration of several microseconds is typical for chemiluminescence in aqueous or aqueous-alcoholic solutions. Luminol luminescence in alcoholic solutions with a high degree of dehydration is not of chemiluminescence nature and can be significantly suppressed in two-quantum excitation.
The features of chemiluminescence kinetics in detection of actinides in solutions are discussed.
This work was financially supported by the ISTC (project no. 3694).
References
[1] I.N. Izosimov, Phys. Prt. Nucl., 38, 177 (2007).
[2] I.N. Izosimov et al, Proc. Int. Conf. Actinides 2005, Manchester, UK, 2005, p. 779.
Author
Igor Izosimov
(Khlopin Radium Institute)
Co-authors
Nikolai Firsin
(Khlopin Radium Institute)
Nikolai Gorshkov
(Khlopin Radium Institute)
Vladimir Mikhalev
(Khlopin Radium Institute)
