A. G. C. Nair’s research while affiliated with Bhabha Atomic Research Centre and other places

Individual separation of rare earth isotopes from lanthanum to lutetium has been carried out using reverse phase partition chromatography and analyzed by γ-ray spectrometric technique. HDEHP from FLUKA and BDH on inert support celite has been used as extracting agent, whereas hydrochloric acid of different molarities was used as eluting agent. Good separation between individual rare earths has been achieved but the elution pattern differs based on the HDEHP from FLUKA and BDH.

The k 0-based internal mono-standard prompt gamma-ray neutron activation analysis (IM-PGNAA) method was used for compositional analysis of a cement standard provided by the International Atomic Energy Agency as a part of inter-laboratory comparison exercise. The PGNAA was also applied to a local cement sample for comparison purpose. The concentration ratios of elements with respect Ca were determined using the internal mono-standard method. The concentration ratios were then converted to the absolute concentrations by determining concentration of Ca in the cement using relative method. Concentrations of 11 elements were determined in both sample and standard of cement. The results of cement standard are found to be in good agreement with the certified values. The uncertainties on the elemental concentrations were in the range of 5–10 %.

Specific parts (fruits and seeds) of different medicinal plants often used in Indian Ayurvedic system were analysed for 18 elements (K, Mn, Na, Fe, Zn, Cu, Co, Br, Sm, Cl, La, Al, Cr, Ca Cd, Ni, Pb and Hg) by employing instrumental neutron activation analysis (INAA) and atomic absorption spectroscopy (AAS) techniques. The samples were irradiated with thermal neutrons in a nuclear reactor and the induced activities were counted by γ-ray spectrometry using efficiency calibrated high-resolution high purity germanium (HPGe) detector. Most of the medicinal plants were found to be rich in one or more of the elements under study. The elemental concentration in different part of medicinal plants and their biological effects on human being are discussed. It is expected that the experimental data on the elemental concentrations will be helpful in the synthesis of new Ayurvedic drugs for the control and cure of various diseases.

Elemental analysis of some medicinal plants used in the Indian Ayurvedic system was performed by employing instrumental neutron activation analysis (INAA) and atomic absorption spectroscopy (AAS) techniques. The samples were irradiated with thermal neutrons in a nuclear reactor and the induced activity was counted by gamma ray spectrometry using an efficiency calibrated high resolution high purity germanium (HPGe) detector. Most of the medicinal plants were found to be rich in one or more of the elements under study. The variation in elemental concentration in same medicinal plants samples collected in summer, winter and rainy seasons was studied and the biological effects of these elements on human beings are discussed.

Ground water samples obtained from West Bengal, India were analyzed for total arsenic and its inorganic species contents by instrumental neutron activation analysis (INAA). Two anion exchange separation methods using Dowex 1X8 in chloride and acetate forms were standardized for the speciation of As(III) and As(V) using radiotracers. The method by Dowex 1X8 in the acetate form was validated using synthetic mixtures of As(III) and As(V), and applied to water samples; the species concentrations were determined by INAA. The accuracy of the INAA method was evaluated by analyzing the NRCC CRM DORM-2 for total arsenic.

An epithermal neutron activation analysis (ENAA) method using boron carbide filter was standardised for the determination of low levels of iodine in various food and food products like milk, milk powder, baby food and health drink powders. The concentrations of iodine were also determined in seven samples of iodised salt used in cooking in India. Advantage of iodine determination by ENAA was evaluated by determining boron ratios of iodine and its interfering elements like Na, K, Mn, Cl and Br. Iodine concentrations were determined in seven biological reference materials obtained from NIST and IAEA, out of which three SRMs were used as the control samples. The results showed that trace levels of iodine can be determined in samples even in the presence of high salt content without chemical separations.

Brahmi (Bacopamonnieri) leaves, known as nervine tonic in Ayurveda, and its aqueous (BA), methanolic (BM) and aqueous–methanolic (BAM) extracts were analyzed for 7 minor (Al, Fe, Na, K, Ca, P, Cl) and 18 trace (As, Au, Ba, Br, Co, Cr, Cu, Hf, Hg, La, Mn, Rb, Se, Sm, Sr, Th, V, Zn) elements by INAA. BAM extract showed maximum contents of Na, K, Cl and significant amounts of Mn, Co, Zn. It was also found as effective scavenger of DPPH radicals with 33.5% total phenolic content, highest γ-ray radioprotective effect and higher anti lipid peroxidation activity.

Elemental analysis of some medicinal plants used in the Indian Ayurvedic system was performed by employing instrumental neutron activation analysis and atomic absorption spectroscopy. The samples were irradiated with thermal neutrons in a nuclear reactor and the induced activity was counted by γ-ray spectrometry using an efficiency calibrated high resolution high purity germanium detector. Most of the medicinal plants were found to be rich in one or more of the elements under study. The elemental concentration in different medicinal plants and their biological effects on humans are discussed.

Instrumental neutron activation analysis (INAA) of fluid catalytic cracking (FCC) catalyst samples was carried out with an objective to identify activable elements and evaluate its suitability for use as an intrinsic radiotracer for tracing catalyst itself in Fluid Catalytic Cracking Units (FCCUs) used in petroleum refining. Two catalyst samples obtained from two different refineries were analyzed. Twelve different elements were identified in each catalyst sample and their respective concentrations were determined. From the recorded gamma-ray spectra, it was found that lanthanum-140 (140La) and sodium-24 (24Na) were the predominantly present and suitable radionuclides that could be used as radiotracers for tracing catalyst in FCCUs. Lanthanum being present in much higher concentration forms the major component of the radiotracer after irradiation.Based on the results of INAA, appropriate quantities of the catalyst samples were irradiated with neutrons to produce the desired amount of activity of lanthanum-140 and sodium-24 to be used as radiotracers for tracing the catalyst itself in a pilot as well as an industrial-scale FCCU. The residence time distribution (RTD) of catalyst was measured and analyzed to determine mean residence time (MRT). The axial dispersion model (ADM) was used to simulate the measured RTD data and investigate the degree of axial mixing. The results of the experiments were used to improve the design of pilot-scale FCCU and optimize the performance of the industrial-scale FCCU.

A summary of k 0-based R&D work on neutron activation analysis (NAA), internal mono standard NAA (IM-NAA) and prompt gamma-ray NAA (PGNAA) is presented. The k 0-based NAA was standardized by characterizing irradiation sites of research reactors, validated using reference materials and applied to samples of different origin. Recently IM-NAA method was developed, validated for small and large size samples and applied for the analysis of large size as well as non-standard geometry samples. Studies on PGNAA included characterization of neutron beam, determinations of detection efficiency and prompt k 0-factors, and analytical applications.