A search for losses of chemical elements during freeze-drying of biological materials

Possible losses of seven chemical elements were investigated in biological tissues during freeze-drying in vacuum. Thyroid glands were taken during post-mortem examination of 23 people died of different diseases. Instrumental neutron activation analysis (INAA) was used to estimate contents of Br, Ca, Cl, I, K, Mg, and Na. The nuclear reator vertical channel with flux density of 1.2·10¹³n·cm^–2·s^–1 was used for neutron irradiation. The analysis was carried out using short-lived radionuclides induced in samples after neutron irradiation. Then thyroids were freeze-dried at below 0 °C in vaccum up to the constant mass (lyophilisation) and then homogenized. Samples of lyophilised and homogenized tissues were again studied by INAA. The lack of difference between the results of the analysis before and after lyophilisation is an evedence of no loss of Br, Ca, Cl, I, K, Mg and Na during freeze-drying of biotissues in vaccum.     

Preliminary study of trace elements in human brain tumor tissues by instrumental neutron activation analysis

Elemental profiles of brain tumor tissues from 15 patients of astrocytomas (grade I–III) and normal human brain tissues of 23 male age matched autopsies as controls have been studied by instrumental neutron activation analysis. The SLOWPOKE reactor with a thermal neutron flux of 8·10¹¹n·cm^–2·s^–1 and swimming pool type reactor with a thermal neutron flux of 1·10¹³n·cm^–2·s^–1 were used for short and long irradiation of samples, respectively. Spectrophotometry was only used for analyzing phosphorus. A total of 18 elements Se, Na, K, Br, Cl, Mn, Mg, S, Ca, Cu, Hg, Cr, Fe, Rb, Zn, Co, Sc and P has been determined for this purpose. The reliability of methods has been checked by analyzing biological standard reference materials horse kidney (IAEA H-8) and bovine liver (NBS SRM 1577a). The analytical results showed that compared with the normal brain tissues, concentrations of Ca, Fe, Cu, Zn, Se, Mn, Br and Sc were significantly higher in tumor tissues (P<0.01) and concentrations of Rb, K and P were lower, while no differences for contents of Mg, S, Cr, Hg, Na and Cl were observed. A negative correlation between P and Ca in malignant and normal brain tissues was observed.     

Instrumental neutron activation determination of rare earth,noble and other elements in mineral raw materials of The Socialist Republic of Vietnam

The possibilities of multielement neutron activation analysis of the mineral raw materials of the Socialist Republic of Vietnam, have been studied. Samples were activated by a²⁵²Cf neutron source (yield 4·10⁹ n·s^–1). The induced activity was measured by coaxial Ge(Li) and planar Ge detectors. The content of gold, thorium, uranium, rare earths and other elements, was determined and evaluated in ores and concentrates by an absolute method.     

Multielemental determination in water by neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been applied to a water sample to determine the elemental concentrations. The sample was irradiated at a neutron flux of 1.2·10¹² n·cm^–2·s^–1 for two different periods followed by counting at three different decay times, using two coaxial type high-resolution Ge(Li) detectors. The dominant elements detected in the water sample are Ca, Cl, Na, Mg, and K present in levels while Co, I, Mn, Sm, and Sb are present in smaller amounts approximately on the average 0.01 ppm. Only traces of other elements such as rare-earth elements, Ag, As, Ba, Cu, Cd, Fe, Sr, W, Zn, seem to be present in the water samples.     

Multi-element determination in silicate rocks by instrumental neutron activation analysis

Instrumental neutron activation analysis technique was applied for the determination of 20 elements in 54 silicate rock samples which belong to three sedimentary geological formations located in the western desert of Iraq. The samples along with USGS standards were irradiated in an IRT-5000 reactor at a neutron flux of 3.7·10¹³ n·cm^–2·s^–1 The following minor and trace element constituents have been determined: Na, K, Ca, Fe, Sc, Cr, Co, Zr, Ce, La, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Th and U.     

Precipitation separation of strontium and calcium from acidic solutions using crown ether and tungstosilicic acid

Strontium forms a compound of composition (SrL)₂A·nH₂O with low solubility (5.0·10^–6 mol Sr·dm^–3) in the presence of 18-crown-6 (L) and tungstosilicic acid (H₄A) in acid media, as has been found by radiometric precipitation titration. Formation of the compound with limited solubility was used for separation of strontium and calcium from 1 mol·dm^–3 HCl. It is possible to separate strontium in the range from trace to 6 mmol·dm^–3 in the presence of calcium with its concentration up to 0.2 mol ·dm^–3 and the recovery determined was 95% of Sr and 5% Ca or 90% of Sr and 4% Ca, respectively. The ratio of Sr/Ca depends on the stability constants ratio of metal-L (⊃_SR/⊃_ca) in the case of gradual addition of L. Potassium up to the concentration of 0.05 mol·dm^–3 does not influence recovery of strontium.     

Separation of fluoride ion by extraction with triphenyltin chloride. Application for NAA of fluorine by means of 14-MeV neutrons

The separation of fluoride by extraction with toluene solution of triphenyltin chloride has been studied. Quantitative isolation of fluoride from solutions with a wide acidity range (pH 4.0–11.5) has been established. It is suggested that interferences by Ca, Mg, Fe, and Al can be avoided by masking these elements using sulfate and hydroxyde ions. Interference by phosphate ions can be overcome in a similar fashion. The halogenated species can be masked by mercury nitrate. Detection limit for fluorine determination is about 3 g for a neutron generator flux of 2·11¹¹ n·cm^–1·s^–1. A method for fluorine assay in water using a neutron generator with a detection limit of 1 ppm has been developed.     

INAA of trace impurities in aluminium clads

As a contribution to nondestructive neutron assay of reactor grade aluminium, a number of elements have been investigated qualitatively and quantiatively using a vertical channel in the IRT-5000 reactor with a thermal neutron flux of 7.6·10¹²n·cm^–2·s^–1. The -ray spectra of irradiated samples were analysed with a 30 cm³ Ge(Li) detector connected to an HP-computer and a 4096 channel analyser. The following impurities have been determined: Sc, Ca, Cr, Fe, Ni, Co, Zn, As, Sb, W, Au, Th and U, while Lu and Hf have been determined qualitatively only.     

Determination of As,Cd, Hg,Cu and Zn in biological samples by radiochemical neutron activation analysis

In this work, a simple group separation scheme based on extraction for NAA determination of trace of As, Cd, Hg, Cu and Zn in biological materials is described. For this purpose, zinc-diethyldithiocarbamate, Zn(DDC)₂, and methyl isobutyl ketone-iodide have been chosen as reagents. The elements can be extracted successively and quantitatively from strong mineral acids without adjusting pH of the solution, and separated into two groups suitable for gamma-ray spectrometry. Samples of 100–200 mg dry weight were double-sealed into polyethylene bags and irradiated in a swimming pool reactor with a thermal neutron flux of 10¹³n·cm^–2·s^–1 for 44 hours. After a cooling period of 1–3 days, the samples were digested with microgram quantities of carrier in concentrated nitric acid and sulfuric acid at 150°C for 3.5 hours in a teflon bomb, then extracted as described above. The reliability of the analytical method was checked using reference materials Horse Kidney IAEA H-8, Human Hair NIES-5 and Tomato Leaves NBS-1573. Most of the results obtained for reference materials agreed with the certified values¹². Chinese autopsy samples of hair and liver were presented.     

Multielement NAA for the characterization of Saudi Arabian rocks

The instrumental neutron activation analysis technique (INAA) was used in the qualitative and quantitative analysis of 48 geological samples from the Umm Al-Birak area in the Kingdom of Saudi Arabia. The samples were properly prepared together with their standards and simultaneously irradiated in a neutron flux of 2.4 ·10¹² n·cm^–2 s^–1 in the reactor facilities of the National Tsing Hua University (THOR) in Taiwan. Gamma-spectra from the high resolution Ge(Li) detector were analyzed using the BRUTAl code. As a result of the analysis of the geological samples, 20 trace elements were identified qualitatively and quantitatively. These elements are: Co, Cr, Eu, Fe, Hf, K, La, Lu, Na, Rb, Sc, Sm, Ta, Tb, Th, U, Yb, Zn and Zr. The concentrations of these elements have been used in the investigations of the geochemistry of the Umm Al-Birak microgranite site using the BMDP computer code of the Ministry of Petroleum and Mineral Resources. This investigation showed that the high grade area is a differentiated rock that crystallized in a late stage of the Umm Al-Birak microgranite area.     

Preparation and characterization of silicate gel glasses containing Cr2O3

The effect of thermal treatment on the structural incorporation of Cr₂O₃ in xCr₂O₃·(100 – x)SiO₂ and 5R _n O·xCr₂O₃·(95 – x)SiO₂ (where x=0.01–1 mol.% and R=Li, Na and Ca) gel glasses was studied by optical absorption spectrophotometry, DTA-TG, XRD and electron microscopy.Samples heat treated at 60°C have green color due to the presence of Cr³⁺ in octahedral coordination. The optical transmission, and color (yellow, orange or ambar), of the samples heat treated between 200 and 700°C prove that Cr³⁺ (octahedrally coordinated) and Cr⁶⁺ (tetrahedrally coordinated) are both present. Segregation of Cr₂O₃ take place at temperatures above 800°C.In reducing conditions the gel glasses were green due to the presence of a high content of Cr³⁺ ions. Samples containing Li or Na show crystalline phases at temperatures below 850°C.     

Speciation of nickel,copper, zinc,and manganese in different edible nuts: a comparative study of molecular size distribution by SEC–UV–ICP–MS

Molecular size distribution patterns of Cu, Mn, Ni, and Zn were determined in several nut species by size-exclusion liquid chromatography (SEC) coupled on-line to UV and inductively coupled plasma mass spectrometry (ICP–MS) for detection. The molecular weight (MW) fractionation of the different metals was performed with a Superdex Peptide column, injecting 100 L of the extracted solutions. The association of the elements with different MW fractions was observed with sequential detection by UV and ICP–MS. Various separation conditions were evaluated to obtain proper resolution and reproducible results with the size-exclusion column. Complete MW information of the elemental fractions in the nut samples was obtained within a retention time of 30 min. Fractionation of the above mentioned elements was done in nine different nut species commonly found in commercial markets. Variability of the fractionation patterns for two different extraction media, 0.05 mol L^–1 NaOH and 0.05 mol L^–1 HCl, was evaluated for every nut sample. Differences in the elemental fractionation patterns were found depending on the extraction procedure, nut species, and the type of element studied. It was also observed that the elements studied showed predominant association with high MW fractions when extracted with basic solution whereas with acidic extraction media only low MW fractions were obtained.     

Intercomparison and determination of environmental standard samples by instrumental neutron activation analysis

To identify and improve the analytical technique for air pollution research, four kinds of environmental standard samples, i.e., airbome particulate matter, coal flyash, soil and pine needle supplied from the NIST and the IAEA were analyzed using thermal and epithermal neutron activation techniques. Sample irradiation was done at the irradiation facilities (neutron flux, 1 · 10¹³ n·cm^–2·s^–1) of the TRIGA MARK-III Research Reactor in the Korea Atomic Energy Research Institute. The accuracy and precision for the analysis of 40 trace and toxic elements in the samples were compared with the certified and reported values, respectively. In the analytical results of all standard reference materials, the relative standard deviation were within the 15% except for 11 elements and the relative error were agreed within the 10–20% except for 13 elements. The benefit of epithermal activation was investigated and the optimum analytical condition is reported.     

Liquid-liquid extraction and spectrophotometric determination of uranium with n-phenyl-3-styrylacrylohydroxamic acid (PSAHA)

A rapid, selective and sensitive liquid-liquid extraction and spectrophotometric method for the separation and microgram determination of uranium using PSAHA is described. Uranium is extracted with PSAHA into chloroform at pH 6.0–6.8. The U-PSAHA chelate is orange red in color having maximum absorbance at 410 nm and molar absorptivity 1.2·10⁴l·mol^–1·cm^–1. The system obeys Beer's Law in the range of 1.2 to 22.00 ppm of uranium. The uranium is determined in sea water and rock samples.     

A gas flow proportional detection system for the determination of boron in aerosol samples and other sample types

This work describes the design, fabrication, and testing of a lucite bodied proportional gas detection system for the analysis of boron in selected samples via detection of the charged particles produced in the 10B(n,)⁷Li reaction induced by thermal neutrons. The detector was designed for internal placement of samples; the sample types of major interest were airborne aerosols collected on filters or particulate impaction plates. Samples were irradiated with the detector in the thermal neutron field produced in the graphite thermal column of the University of Lowell's one megawatt research reactor. Determined sensitivities for boron varied from 6.2·10^–8 to 1.73·10^–6 cpm·ng^–1 (n·cm^–2J·s^–1)^–1 depending on the physical characteristics of the samples. For a nominal counting time of ten minutes the lower limit of mass detection of natural boron was determined to be 12.1 nanograms. The analytical method was applied to the estimation of boron in fourteen samples of natural aerosols collected on membrane filters. Analysis of prepared samples and natural aerosol samples by ICP emission showed good agreement with analysis via the (n,) reaction. Application of the method to other sample types was demonstrated by the determination of boron in samples of borosilicate glass and borated polyethylene.     

Neutron activation and radiochemical separation of selenium from environmental and food samples from and around Bombay using ethyl-α-isonitrosoacetoacetate

Neutron activation analysis has been applied for determination of selenium in environmental and food samples. Food and environmental samples from city, industrial and agricultural zones were collected with utmost care. Samples were activated in the flux 1·10¹³ n·cm^–2·s^–1 in the CIRUS reactor of BARC, Bombay, 75-Se was separated from 6.5N HCl solution using ethyl--isonitrosoacetoacetate (HEINA) reagent. The decontamination studies showed the method is very selective. Selenium contents of wheat, rice, vegetables, cereals pulses etc. and of soil, water, and deposits on plants and surface were determined by the procedure developed.     

Pulse radiolysis of Triton X-100 aqueous solution

Pulse radiolysis of deaerated aqueous solutions of 4·10^–5–2.4·10^–3 mol dm^–3 Triton X-100 gives rise to a transient species originating from the reactions of OH radicals and H atoms. The rate constants of these reactions were found to be 8.8·10⁹ mol^–1·dm³·s^–1 and 1.25·10⁹ mol^–1·dm³·s^–1, respectively, for Triton X-100 concentrations below CMC. The corresponding transient species were found to decay according to second order kinetics. The mechanism of the reactions involved including concentration effects is discussed.     

Analytical possibilities of the BOR 60 reactor

The analytical potential of a fast neutron reactor has been studied. The maximum density of the neutron flux is 2.5·10¹⁵ cm^–2·s^–1 at a maximum energy of 450 keV. The determining reaction for activation analysis at this reactor is an (n, n) reaction. The possibility of selectively determining Pb, Hg, Cd, Au, Ag and other elements at a level of 10^–5–10^–8% is demonstrated. This activation technique allows rapid determination of these elements.     

Multielement determination in river water by neutron activation analysis

Concentrations of Al, Br, Ca, Ce, Co, Cr, Eu, Fe, Hf, La, Lu, Mg, Mn, Na, Rb, Sc, Sm, Sr, Tb, Th, Ti, V, Yb, Zn, and Zr have been measured in Tigris and Euphrates river water, using neutron activation analysis in combination with preconcentration technique. River water samples were preconcentrated by evaporation at 70°C under atmospheric pressure. The samples with standard reference materials were irradiated with a neutron flux of 2.3·10¹³ n·cm^–2·s^–1.     

Study of the correlation of trace elments in human hair and internal organs by NAA

24 male autopsy cases aged 35–60 years have been collected from Shanghai China to study the relationships between human hair and internal tissues. Autopsy samples of hair, kidney-cortex, liver and lung were analyzed. A radiochemical neutron activation analysis (RNAA) based on a simple group extraction scheme was used for measuring the trace elements As, Cd, Hg, Cu and Zn. Zinc diethyldithiocarbamate Zn(DDC)₂ and methly isobutyl ketone-iodide have been chosen as reagent. Trace element of Se was determined by instrumental neutron activation analysis (INAA). A SLOWPOKE reactor with a thermal neutron flux of 8·10¹¹ n·cm^–2·s^–1 and a swimming pool type reactor with a thermal neutron flux of 1·10¹³ n·cm^–2·s^–1 were used for short and long irradiation of samples, respectively. The reliability of methods has been checked by analyzing biological standard reference materials Horse Kidney (IAEA H8), Tomato Leaves (NBS 1573) and Human Hair (NIES-5). The analytical results show that toxic elements As, Cd and Hg exist in a larger individual variability than the essential elements of Cu, Se and Zn for each tissue. A linear regression analysis related to the six elements of primary interest for the IAEA Coordinated Research Program (CRP) has been done by a computer program for each pair of hair-tissue. A positive correlation is found between concentration of As in hair and kidney-cortex, the correlation coefficient r is 0.751 (p<0.01). Positive correlations between concentration of Se in hair and liver, kidney-cortex and lung are also observed in this study. It shows that the elements As and Se in hair may be useful indicators for assessing certain internal tissues of normal persons. A comparison of Cd concentration in lung shows a significant difference between smokers and non-smokers. A significant correlation between element Cd and Zn in kidney-cortex is also presented in this paper.