A radiochemical method has been devised for the separation of bismuth activities of the natural series,viz.214Bi,210Bi and212Bi, and applied to the indirect estimation of their corresponding precursors,222Rn,210Pb and212Pb, in a wide variety of geological materials. The method consists of the solvent extraction of bismuth in radiochemically
pure form from the sample solution atpH 2 with diallyldithiocarbamido-hydrazine (Dalzin) in chloroform, and back extraction with 2M acid. The advantages of this method over the dithizone extraction system are discussed.
Authors:S. Gangadharan, V. Lakshmi, and M. Sankar Das
Correlations between the growth of hair and the trace element profile have been investigated by non-destructive neuron activation
analysis through gamma-ray speetrometry using NaI(Tl) as well as Ge(Li) detectors. After preliminary investigations to establish
the experimental errors, the effect of washing procedures and in-person variations, hair samples belonging to ladies with
known case histories, particularly with regard to dietary habits, health and profession, were examined. Scalp-hair samplex
50–100 cm in length, representing an average time span of ∼5–10 years were collected by combing. Samples in their non-anagen
phase, differentiated by their roots, were analysed in 10 cm sections. The concentrations of the following elements were determined:
Na, Cl, Mn, Co, Cu, Zn, As, Se, Ag, I, Au and Hg. Absolute values for the concentrations are reported for most of the elements,
while for the rest relative values for the various sections are given. The values for the different sections vary by large
factors for many elements although for some elements, like Cu and Mn, the variations are not appreciable. The unusually large
concentrations of elements like Se ang Hg are in broad agreement with the case histories. However, detailed examination of
the results with regard to time-dependent variations seem to pose serious problems in the applications to forensic science.
Various methods of preparing standards for activation analysis have been reported in the literature. This paper describes
the feasibility of preparing ion exchange resin based standards containing predetermined levels of ions. Using a solution
of known initial concentration of the ion, and given the value of its distribution coefficient, it is possible to predict
the resin concentration that will be obtained. Resins containing ppm levels of copper and manganese have been prepared and
their stabilities evaluated over a period of time. The feasibility of preparing a multielement standard has been studied with
five rare earth elements (La, Ce, Sm, Eu and Dy).
234U to235U activity ratios were determined in some of the primary and secondary uranium minerals. The conditions for the accurate measurement
of this ratio by α-spectrometry were optimized. The activity ratios of234U to238U in U4+ and U6+ fractions were determined. This ratio was found to be more than the equilibrium value in one leaching experiment and is explained
as due to the oxidation and selective removal of the234U, relocated by α-recoil. Age values of some of the minerals, which had earlier been dated assuming this ratio to be one,
were rectified when necessary.
Authors:S. Gangadharan, M. Das Sankar, and S. Yegnasubramanian
The instrumental approach to the determination of elements through annihilation radiation demands a high degree of specificity
which has not been fully met by the high resolution Ge(Li) or the two detector (180°) coincidence spectrometry. The triple
coincident measurement of the three gamma quanta resulting from the triplet state annihilation of e−−e+ system provides enhanced specificity, although at a loss of sensitivity. The development of this approach for the measurement
of annihilation radiation is decribed with the determination of copper in orchard leaves as an illustrative example.
Authors:G. Reddy, D. Pant, B. Rao, and M. Das Sankar
A scheme of analysis for the determination of Na, Mn, U, Th, Hf, Sc, La, Ce, Eu, Tb, Co, Rb and Cs in geological samples using
the neutron activation technique has been described. The results obtained in this work on eight geological standard rocks
and a trachyte are presented and compared with literature data.