K. Rengan

TRACE ELEMENT CORRELATIONS WITH AGE AND SEX IN HUMAN FINGERNAILS

Concentrations of 17 elements in fingernails of 92 control individuals with ages ranging from 4 months to 93 years living in a relatively non-industrial environment were determined by instrumental neutron activation analysis (INAA). Statistical analysis demonstrated several different patterns of trace element correlation with age and sex. Bromine, Co, Cr, Fe, Na and Sb were found to be negatively correlated (p<0.05) with age, while Zn was positively correlated (p<0.05). Silver, Au, Se, and Zn concentrations were found to be higher in females than in males. Males had higher concentrations of Na and K than females. Significant interelement correlations were also observed. The age and sex variations observed should prove to be useful in the proper interpretation of elemental imbalances associated with degenerative neurological diseases, especially in view of recent reports that markers for AD have been detected in external tissue.

Chelating resins: Sorption characteristics in chloride media

The chelating resins Dowex A1 and its purified form, Chelex 100, contain the iminodiacetate functional group. The resins can exchange cations from solutions of high pH and anions from low pH solutions. Further, the iminodiacetate functional group provides chelating capability leading to special selectivity for multivalent ions such as Sb(V) and Hg(II). A systematic study of the sorption characteristics of Chelex 100 was initiated in our laboratory. Distribution coefficient values (Kd) were measured for Zn(II), Cd(II), Sn(IV), Sb(V) and Hg(II) as a function of HCl concentration and for Cu(II) and Pb(II) as a function of pH. The results obtained thus far indicate that Sb(V) and Hg(II) have high Kd values in acid chloride solutions. A radiochemical separation procedure was developed for the determination of Hg by neutron activation analysis using sorption onto Chelex 100.

Determination of trace level mercury in biological and environmental samples by neutron activation analysis

Sorptivity studies with Chelex 100 column indicated chloride to be the best medium for the sorption of mercury. A radiochemical separation procedure has been developed for the determination of mercury by neutron activation analysis utilizing sorption of mercury on Chelex 100. The method was checked with Orchard Leaves and Tuna Fish standards from the National Institute of Standards and Technology.

The study of distribution coefficients of silver and mercury with chelating ion-exhange resin Dowex A-1

The distribution coefficients (DC) for HgCl42−, Hg(SO4)22−, Hg(NO3)42−, Ag+, Ag(SCN)2− and Ag(NH3)2+ between aqueous solutions and Dowex A-1 were measured in varying hydrogen ion concentrations. The DC of Ag+ in the NO3− media was very low (4 to 6). The DC for the Ag(SCN)2− complex decreased as pH increased. The Ag(NH3)2+ complex had a constant DC of about 65 from pH 8 and above. The trend observed for three mercury complexes in HCl, H2SO4 and HNO3 was similar; the DC decreased steadily from 0.1M to 6M. The HgCl42− complex had the highest DC (9000) while the Hg(NO3)42− complex had the lowest DC (2000).

Sorption characteristics of chelating resins

Chelating resins are used for preconcentrating metal ions in trace analysis. As part of a systematic study of sorption characteristics of the chelating resin Chelex 100, the sorption of Zn(II) and Cd(II) in different aqueous media was investigated. The distribution coefficient (DC) values for both Zn(II) and Cd(II) were extremely low (<4) in 0.5 to 6M HNO3 and H2SO4 solutions. In HCl solution, theDC values for both Zn(II) and Cd(II) were higher, reaching a peak of nearly 40 in 3M HCl solutions. TheDC values for both Zn(II) and Cd(II) increased with increasing pH in chloride, nitrate, and sulfate solutions (0.1M); the value was nearly 104 for both Zn(II) and Cd(II) between pH 5 and 7 and pH 6 and 8, respectively.

Simultaneous determination of arsenic and antimony in environmental samples by radiochemical neutron activation analysis

A radiochemical separation procedure using an inorganic exchanger, tin dioxide (TDO), for the separation of arsenic from antimony is reported here. This separation avoids the interference of 564 keV gamma-ray of122Sb in the measurement of the 559 keV gamma-ray of76As in neutron activation analysis. Environmental samples, after neutron irradiation and digestion, are taken up in 1M HCl–0.1M HF and passed through a TDO column which selectively retains arsenic. The effluent from the TDO column, after proper conditioning, is passed through an anion exchange column for quantitative retention of antimony. The procedure has been utilized for arsenic and antimony determination in NBS Orchard Leaves and NBS Albacore Tuna.

Sorption of silver ions by Chelex 100 chelating resin

Sorption of Ag+, Ag(NH3)n+, and anionic complexes of silver with chloride and thiocyanate ions by Chelex 100, a chelating resin, were investigated systematically. The results are utilized to interpret the seemingly contradictory data available in the literature

EFFECT OF REAGENT CONCENTRATION ON CERENKOV COUNTING EFFICIENCY

Cerenkov counting is often regarded as a modified version of liquid scintillation counting in which chemical quenching is not manifested. However, the mechanism of Cerenkov counting is such that changes in the concentration of reagents in the counting medium results in changes in Cerenkov counting efficiency. Large changes in counting efficiency occur for nuclides with low average beta energy values (Ēβ). The percent increase in Cerenkov counting efficiency in 4M HCl (relative to water) for various nuclides was found to be a smooth function of Ēβ. The relative change in counting efficiency for24Na,32P,42K and204Tl in HCl, NH4Cl and/or NaCl media are presented. The data emphasizes the need to keep the concentration of various chemicals in Cerenkov counting media constant, especially for nuclides with low Ēβ, values, in order to reproduce counting efficiency.

A gas-jet system for the study of short-lived, light fission products

For the study of short-lived fission products, a gas jet system has been set up in a beam port of the Ford Nuclear Reactor at the University of Michigan. The system consists of a target chamber joined to three polyethylene tubes which serve as gas inlet, fission product outlet and an outlet for pressure monitoring. The target chamber is housed in a 7.6 cm (ID) aluminum tube supported inside a radial beam port. This tube can be withdrawn by ∼1 m, allowing the target chamber to be positioned either close to or ∼1 m from the core. The aluminum tube is surrounded by water, which provides shielding and protects the target when not in use (at ∼1 m position). The target is ∼1 mg of235U, chemically plated on an aluminum planchett. The uranium is covered with 2.7 mg·cm−2 of aluminum. The aluminum covering stops most of the heavy fission fragments; the light fission fragments pass through the foil and are thermalized in a gaseous mixture of nitrogen and ethylene. The transport time of fission products from the target chamber to the detector position was measured to be 970 msec. Preliminary experiments indicate that the transport time can be reduced further. The gas jet system is being utilized for the development of fast, gas-phase chemistry for the separation of bromine from fission products.

DETERMINATION OF ARSENIC IN SOME LAKE MICHIGAN FISH USING NEUTRON ACTIVATION ANALYSIS

The level of arsenic in six different species of fish collected from Lake Michigan near Saugatuck, Michigan has been measured using radiochemical neutron activation analysis. The arsenic concentration was found to vary from 0.05 μg/g (wet weight) for yellow perch fillet to 1.4 μg/g (wet weight) for eviscerated bloater chubs. A significant correlation was observed between arsenic concentrations and number of years in the lake for lake trout; correlations were also observed between arsenic concentrations and length of lake trout and smelt. No such correlations were found for alewife or yellow perch.