S. Gangadharan

Application of poly(aniline) as an ion exchanger for the separation of palladium, iridium, platinum and gold prior to their determination by neutron activation analysis

The distribution coefficients of PdIII, IrIV and AuIII on poly (aniline) in 0.1–10 mol l–1 HCI were determined. They are strongly adsorbed at low acidities and the extent of adsorption decreases with increase in acidity, except for AuIII. Palladium, Pt and Au are quantitatively eluted with 5% thiourea in 0.05 mol l–1 HCI whereas the recovery of lr is >90% with 1% ascorbic acid followed by 10 mol l–1 HCl. It was found that Cr, Fe, Co, Ni, Zn, Ga and Ge are not retained on poly(aniline) at low acidities. This separation procedure was applied prior to the determination of Pd, lr, Pt and Au in iron meteorite and PCC-1 standard rock by neutron activation analysis.

Growth of hair and the trace element profile a study by sectional analysis

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.

Determination of cross section of α-induced nuclear reaction on natural Cr and Zr by stacked foil activation for thin layer activation analysis

Abstract The cross sections of different α-induced nuclear reactions on natural chromium and zirconium have been determined at different energies of the α-particles by the stacked foil activation technique using the 40 MeV α-beam from Variable Energy Cyclotron at Calcutta. The reaction channels studied from the stable isotopes of natural Cr and Zr are (α, x n), (α, p), (α, p x n) and (α, αn) (where x = 1 and 2). The excitation functions have also been reported for the energy range from 10 to 40 MeV of α-particles. The experimentally determined cross sections have been compared with the theoretical values computed on the basis of the hybrid model using a program ALICE 85/300. The analytical validation of the experimental values has been carried out with a vanadium target for which cross sections are already reported in the literature. The purpose of generating of the above cross sections is to support the thin layer activation technique for the study of surface wear in Cr and Zr based metals/alloys.

Elemental characterisation through instrumental neutron activation

Neutron activation has been used to characterise the elemental composition of geological and biological materials. Both reactor neutrons and 14 MeV neutrons have been used. Instrumental approach has been followed incorporating coincidence measurements. The system and the methodology have been discussed. The results for the 3 Canadian rock standards (SY-2, SY-3, MRG-1), a trachyte, 2 NBS SRMS (1571 Orchard leaves, 1577 Bovine liver) and an IAEA intercomparison sample, Animal Muscle H.4 have been given for 15–25 elements.

Polyaniline, a conducting polymer, as a standard for hydrogen profiling on material surfaces

Abstract The behaviour of polyaniline, a conducting polymer, under 15N3+ ions bombardment and its subsequent utility as a standard for hydrogen estimation using the nuclear resonance reaction 1H(15N,αγ)12C have been investigated. Polyaniline withstands higher doses of radiation compared to other polymeric materials like polyethylene, polypropylene etc. used as standards for hydrogen estimation without any special sample handling arrangements.

Measurement of annihilation radiation in activation analysis: Enhancement of specificity through triple coincidence

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.

Neutron activation analysis of lithium niobate

A radiochemical neutron activation analysis procedure for the determination of Ta, W, Ir, Pt, Au, Cu, Cr, Co and Zn in lithium niobate has been developed. The method involves a one-step removal of radioactive nuclides of Nb, Ta and W representing the dominating radioactivity of the irradiated sample. After irradiation, the sample is fused with inactive carriers and Na2O2 in a nickel crucible. The fused cake is dissolved in HCl−H2O2 and Nb, Ta and W are homogeneously precipitated. The impurities are separated by combinations of precipitation and ion-exchange separations for precise γ-ray measurements with an overall chemical yield of 70% to 90%. The results are discussed.

MULTIELEMENT ANALYSIS OF MINOR COMPONENTS USING A 14 MeV NEUTRON GENERATOR

Abstract14-MeV neutron activation has been used for the determination of F, Al, Si, P, K, Mn, Mo and W in minerals and steel. Most of these elements have been estimated simultaneously through gamma-ray spectrometry. The evaluation of the effects of interferences is discussed and the sensitivities are given. The main features of the neutron generator fabricated in this Centre and used in this work are briefly described.

Determination of oxygen impurity in high purity materials by charged particle activation analysis using alpha projectiles

Abstract40 MeV α-particles have been used to determine oxygen impurity at ppm levels in silicon, copper, and stainless steel, through the radiochemical separation of18F from the matrix. The separation of18F has been carried out by two techniques, viz.(1) distillation of H2SiF6 and (2) precipitation of KBF4 and some modification has been applied in the separation, depending on the nature of interferences from the matrix. Instrumental approach was also carried out to determine the oxygen impurity at ≥ 100 ppm in Si matrix because this approach is not possible in Cu and stainless steel samples due to matrix activity.

Derivative activation analysis of phosphorus at ppb levels in water samples

A neutron activation analysis procedure has been developed for the indirect determination of phosphorus as orthophosphate at ppb levels, via the formation of antimonyl phosphomolybdic acid. The complex is adsorbed on Sephadex G-25 resin and the antimony is estimated through NAA, allowing the determination of phosphorus. The procedure provides an easy method to adopt for the routine determination of phosphorus at ≧10 ng ml−1 levels with good precision, in water samples.