Daisy Joseph

Elemental analysis of selected Indian monazite ores by energy dispersive X-ray fluorescence/EDXRF/spectroscopy

Analysis by Energy Dispersive X-ray Fluorescence spectroscopy of monazite ores from Kerala /Chavara and Manavalakurichi/, Orissa /Chattrapur/ and Tamil Nadu /Tirunelveli/ has been carried out for the determination of their elemental composition using109Cd /annular/ and241Am /disc/ radioisotope sources. The elements Y, Zr, Mo, Pb, Th and U were analyzed using a109Cd source, and the elements La, Ce, Pr, Nd, Sm, Gd and Dy were analyzed using the241Am source in side source geometry. Quntitative results on these 13 elements present in these ores were obtained by the EDXRF technique. It was seen that despite the diverse geological settings, there is remarkable similarity in the elemental composition of these ores, although some trace elements do show certain variations from sample to sample. These results are presented and discussed in this paper.

Depletion of reduction potential and key energy generation metabolic enzymes underlies tellurite toxicity in Deinococcus radiodurans

Oxidative stress resistant Deinococcus radiodurans surprisingly exhibited moderate sensitivity to tellurite induced oxidative stress (LD50 = 40 μM tellurite, 40 min exposure). The organism reduced 70% of 40 μM potassium tellurite within 5 h. Tellurite exposure significantly modulated cellular redox status. The level of ROS and protein carbonyl contents increased while the cellular reduction potential substantially decreased following tellurite exposure. Cellular thiols levels initially increased (within 30 min) of tellurite exposure but decreased at later time points. At proteome level, tellurite resistance proteins (TerB and TerD), tellurite reducing enzymes (pyruvate dehydrogense subunits E1 and E3), ROS detoxification enzymes (superoxide dismutase and thioredoxin reductase), and protein folding chaperones (DnaK, EF‐Ts, and PPIase) displayed increased abundance in tellurite‐stressed cells. However, remarkably decreased levels of key metabolic enzymes (aconitase, transketolase, 3‐hydroxy acyl‐CoA dehydrogenase, acyl‐CoA dehydrogenase, electron transfer flavoprotein alpha, and beta) involved in carbon and energy metabolism were observed upon tellurite stress. The results demonstrate that depletion of reduction potential in intensive tellurite reduction with impaired energy metabolism lead to tellurite toxicity in D. radiodurans.

Characterization of gem stones (rubies and sapphires) by energy-dispersive x-ray fluorescence spectrometry

Trace elemental analyses of rubies and sapphires from different countries of origin were carried out by the EDXRF technique. It was found that K, Ti, Cr, Fe, Cu, Zn, Sr and Ba are generally present in natural rubies and Cr, Ni, Cu and Zr in synthetic ruby. The synthetic ruby shows a clean spectrum devoid of iron whereas the presence of Fe is seen in all the naturally occurring rubies irrespective of the country of origin. The elements present in Indian sapphires are Ca, Fe, Sr and Mo and their estimated concentrations are 0.10, 0.18, 0.029 and 0.006%, respectively. Further, preliminary XRD studies showed patterns of synthetic rubies different from those of the naturally occurring rubies. The results demonstrate that EDXRF can be used to distinguish between natural and synthetic rubies. Copyright

Study of trace element correlations with drought tolerance in different sorghum genotypes using energy-dispersive X-ray fluorescence technique

Drought-tolerant and drought-susceptible genotypes of sorghum (Sorghum bicolor L. Monech) were analyzed by the energy-dispersive X-ray fluorescence (EDXRF) technique to study the correlation of trace elements with drought-tolerance capacities. Samples prepared from mature seeds, young seedlings, and old plants were analyzed using a 109Cd radioisotope source and a Si(Li) semiconductor detector of resolution 170 eV for 5.9-keV MnK{ie255-1} X-rays. Elements such as K, Fe, Cu, Zn, Rb and Sr and Y were found to be present in varying concentrations in different samples. The trace element profile studied in the seeds of 11 genotypes and in seedlings (young and old) of 4 sorghum genotypes showed considerable variation. The genotype Arfa Gadamak (AG) showed a distinct presence of a high level of Zn in its young seedling. It was observed that in most of the genotypes (seeds), K and Fe concentrations were more in the tolerant genotype as compared to the susceptible type. The concentration of Fe decreased with maturity in the tolerant group and it increased with maturity in the susceptible group.

Studies of blood lead levels in children by proton-induced X-ray emission (PIXE)

Blood lead levels of children admitted to Sion Hospital, Bombay (India), from the adjoining Dharavi slum areas have been determined by proton-induced X-ray emission (PIXE). Blood samples were collected from 36 children with suspected lead poisoning and from 20 control children. The analysis showed that the lead concentration of the patients varied from 0.1 to 6.0 micrograms ml-1. In addition to lead, K, Ca, Fe, Cu, Zn, Se, Br and Rb were also detected simultaneously, of which the concentrations of Fe, Cu, Zn, Se, Rb and Pb were determined. The high blood lead levels of the children from this area may be ascribed to environmental pollution due to heavy vehicular traffic and industrial sources.

STUDY OF TRACE ELEMENT ABNORMALITIES IN BLOOD OF CHRONIC RENAL FAILURE (CRF) PATIENTS BY PROTON-INDUCED X-RAY EMISSION (PIXE)

A study of trace element abnormalities in serum of uremic patients has been carried out by Proton-induced X-ray emission (PIXE) in the case of non-dialysed, hemodialysed and post-transplantation. Forty two patients and eight healthy controls selected for this study were grouped on the basis of their Serum Creatinine (SC) levels. Serum samples of these subjects were converted into solution by acid digestion and the solutions were micropippetted and dried on a thin mylar sheet to be mounted on a sample holder of the PIXE chamber. Proton beam from Van de Graaff accelerator (Trombay, India) of 2.5 Mev energy was employed for exciting the characteristic X-rays of the elements present in the samples and their X-rays were detected by a Si(Li) detector. The results obtained showed significant abnormalities in the concentration levels of Ni, Cu, Br, SrandPb amongst various groups. Ni was found to be significantly higher in all the groups compared to controls. Concentration of Cu was also found to be high in the sera of patients on hemodialysis as compared to controls and non-dialysed uremics. Cu levels returned to normal after transplantation. Br was lower in patients undergoing hemodialysis which returned to normal after transplantation. Sr was found to be higher in all groups of renal failure as compared to controls. Patients on hemodialysis accumulated significant quantities of Pb which was found to decrease after transplantation. No significant abnormalities were observed in the case of the elements Zn, Se and Rb.

PIXE STUDIES USING THE VAN-DE-GRAAFF ACCELEARTOR AT BARC, TROMBAY – DIFFERENCES IN ELEMENTAL CONCENTARTIONS IN BLOOD SAMPLES OF CHILDREN

Metal monitoring is one of the major concern of biological and bio-medical research. The Proton Induced X-ray Emission (PIXE) which is a multi elemental and non-destructive technique for trace element analysis has been set up at the Folded Tandem Ion accelerator (FOTIA) at BARC, Trombay, Mumbai, India. A few of the bioscience applications carried out at the Van de Graaff Laboratory using PIXE will be summarized in this presentation. Tea leaves obtained from the eastern region of India were analyzed by PIXE using 2.5 MeV protons. Trace elements such K, Ca, Ti, Cr, Ni, Mn, Fe, Cu, Zn, Rb and Sr were present in varying concentration in the tea leaves. The soil analysis showed Ti, Y, Zr and Nb in addition to the elements shown in the leaves. Blood samples of children exposed to vehicular traffic exhaust were analyzed for its Pb content and it was seen that the concentrations of Pb in the blood of the children were high (6.0 μg/ml). Pb poisoning of air due to vehicular exhaust is a major concern and cause for air pollution leading to high blood lead levels in children.

Elemental analysis of Cu−Ni and Nd−Al alloys and, nickel and iron powders by energy dispersive X-ray fluorescence (EDXRF) technique

Energy dispersive X-ray fluorescence spectroscopy (EDXRF) has been used for elemental analysis of Cu−Ni alloy, neodymium aluminide, and iron and nickel powder. The preparation of Cu−Ni alloy and neodymium aluminide has been carried out by aluminothermic reduction of mixed oxides of copper and nickel and neodymium oxide respectively. Aqueous electrorefining technique has been followed for the preparation of iron and nickel powder using Fe−Ni alloy as anode. The determination of major and trace elements present in the Cu−Ni and, electrolytically refined nickel and iron has been accomplished by EDXRF using Cd109 radioisotope source. In the case of Nd−Al alloy Am241 radioisotope source has been used. The rapid and multielement analysis of the thermit product by EDXRF has aided in the appropriate variation of the charge constituents during the standardization of the optimum charge composition for Cu−Ni alloy. EDXRF analysis of electrolytically refined nickel and iron revealed heavy contamination of iron in nickel as compared to that of nickel in iron. Neodymium content has been found to be 67.68% in Nd−Al alloy.

Elemental analysis by radioisotope-excited XRF during thermit smelting of ferrovanadium and niobium

The energy-dispersive x-ray fluorescence (EDXRF) technique was applied to the determination of major and trace elements present in aluminothermically smelted ferrovanadium and niobium. Rapid and multielemental analysis of thermit feed and product aided in the appropriate alterations of the charge constituents to obtain the optimum charge composition. The results of analysis by the EDXRF method were verified using wet chemical analysis for a few typical samples of the product and were found to be in close agreement.

Application of the radioisotope excited X-ray fluorescence technique in charge optimization during thermite smelting of Fe-Ni, Fe-Cr, and Fe-Ti alloys

A wide range of ferroalloys are used to facilitate the addition of different alloying elements to molten steel. High-carbon ferroalloys are produced on a tonnage basis by carbothermic smelting in an electric furnace, and an aluminothermic route is generally adopted for small scale production of low-carbon varieties. The physicochemical principles of carbothermy and aluminothermy have been well documented in the literature. However, limited technical data are reported on the production of individual ferroalloys of low-carbon varieties from their selected resources. The authors demonstrate her the application of an energy dispersive X-ray fluorescence (EDXRF) technique in meeting the analytical requirements of a thermite smelting campaign, carried out with the aim of preparing low-carbon-low-nitrogen Fe-Ni, Fe-Cr, and Fe-Ti alloys from indigenously available nickel bearing spent catalyst, mineral chromite, and ilmenite/rutile, respectively. They have chosen the EDXRF technique to meet the analytical requirements because of its capability to analyze samples of ore, minerals, a metal, and alloys in different forms, such as powder, sponge, as-smelted, or as-cast, to obtain rapid multielement analyses with ease. Rapid analyses of thermite feed and product by this technique have aided in the appropriate alterations of the charge constitutents to obtain optimum charge consumption.