Preconcentration neutron activation analysis of lanthanides by cloud point extraction using PAN

Summary Methods for the simultaneous preconcentration of lanthanides by cloud point extraction and their determination using neutron activation analysis have been developed. The preconcentration method involves the use of a nonionic surfactant and a chelating agent. A fairly small volume of surfactant-rich phase was obtained under optimized experimental conditions, leading to detection limits between 0.3 and 3.0 ng ^. g^-1. Critical parameters that influence extraction efficiency were solution pH and concentration of chelating agent, and to a lesser extent, ionic strength and temperature. Most of the chelates were quantitatively extracted (>90%) at high pH values. Selective separation can be achieved by varying some of the experimental conditions.     

Preconcentration of inorganic mercury and organic mercury with solvent extraction for neutron activation analysis

A preconcentration method combined with neutron activation technique for the analysis of organic and inorganic mercury in waste water samples at ppb levels is presented. The inorganic mercury is extracted in CCl₄ solution with lead diethyldithiocarbamate reagent and the organic mercury is extracted in C₆H₆ solution. Interfering activities of sodium and bromine are removed from the irradiated samples by this procedure. Two different solvent extraction procedures are also described in detail.     

Determination of mercury in bismuth by neutron activation analysis

A method has been developed for the determination of traces of mercury in bismuth by neutron activation analysis. After sample irradiation at a flux of 7 · 10¹³ n cm^-2 s^-1 for 20 min, mercury was separated from bismuth by addition of ammonium sulfide and re-dissolution of bismuth (matrix) sulfide with nitric acid, and filtration of sulfur containing mercury on a membrane filter. The activity of the 68- or 68–77-keV region, counted with a Ge(Li) or NaI(Tl) detector, was used for quantitative measurements. The method was applied to bismuth samples containing 0.1–100 p.p.m. of mercury.     

Determination of bismuth in lead by neutron activation analysis

Neutron activation analysis for bismuth in lead was performed through the separation and measurement of²¹⁰Po, using two different extraction procedures. The reproducibility of the results was good for lead containing bismuth in higher concentrations. For high purity lead, variations in the bismuth content have been found by different analyses of the same sample, owing to inhomogeneity in the distribution of the Bi metal traces. An independent analysis of the same lead samples gave comparable Bi concentrations.     

Extraction of gold and mercury from sea water with bismuth diethyldithiocarbamate prior to neutron activation—γ-spectrometry

Gold and mercury in sea water can be selectively extracted by bismuth diethyldithiocarbamate into chloroform at pH ?1. The matrix species and many other trace elements in the system are effectively removed during extraction. When neutron activation—γ-spectrometry is used, the detection limits for gold and mercury are 0.001 and 0.01 μg 1^?1, respectively. The relative precision is 9% for gold and 13% for mercury.     

Solvent extraction of lead,silver, antimony and thallium with zinc dibenzyldithiocarbamate and its application to the separation of bismuth from large amounts of lead

Solvent extraction of lead, silver, antimony and thallium from various acid solutions was investigated with zinc-DBDTC as chelating reagent. These metals were quantitatively extracted over a wide range of acidity with 0.03% zinc-DBDTC solution in carbon tetrachloride. A separation procedure for bismuth from large amounts of lead was developed; bismuth was extracted from 1 M nitric acid with zinc-DBDTC and was separated from lead by subsequently washing the organic phase once with 3.5 M hydrochloric acid or twice with 3 M hydrochloric acid. Satisfactory results were obtained in separating microgram amounts of bismuth from 1 g of lead.     

Preconcentration techniques for trace analysis via neutron activation

A review is given of the methods that have been proposed for enrichment of trace elements in samples that are to be analysed by neutron-activation methods. The emphasis is on classification of methods, with full illustrations by means of practical examples.     

Determination of Se(IV) in water by neutron activation analysis after coprecipitation of metal dibenzyldithiocarbamate with phenolphthalein

A neutron activation analysis method for the determination of Se(IV) in natural waters is described. It is based on the coprecipitation of the metal dibenzyldithiocarbamate with phenolphthalein. The precipitate is collected on 0.45 m membrane filters and selenium is determined by instrumental neutron activation. A Se(IV) radiotracer (⁷⁵Se, T=120 d) was used to establish optimum conditions and to evaluate the chemical yield. Samples of sea and canal water were analyzed.     

Multielement analysis of Northwestern Nigerian rocks by instrumental neutron activation analysis

Rock samples from seven different locations in northwestern Nigeria were analyzed by reactor instrumental neutron activation analysis and Ge(Li) gamma-ray spectrometry. Concentration values were obtained for 18 elements (As, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Sc, Sm, Sr, Ta, Tb, Th, U, Yb). The geochemical implications of the results are discussed.     

Determination of indium in standard rocks by neutron activation analysis

A rapid neutron activation method for the determination of indium in rocks, based on 54 min (116m)In, is described. The method has been applied to a series of geochemical standards including granite G-1 and diabase W-1. The precision is better than +/- 5% for samples containing more than 5 x 10(-10)g indium. Good agreement with previously published values for G-1 and W-1 has been obtained.     

Preconcentration on hydrous magnesium oxide for neutron activation analysis

It was found that trace amount of various ions could be effectively adsorbed onto hydrous magnesium oxide from aqueous solution. Attempts were made to investigate the feasibility of using hydrous magnesium oxide as preconcentration agent for neutron activation analysis (NAA). The procedure was successfully applied for the measurements of trace amounts of elements in the surface water of a number of large rivers which play very important roles in the lives of local people. Some of them are polluted rather badly. In order to improve the living standards it is rather important to establish reliable analytical methods so that more effective surveillance may be enforced on pollution control problems. NAA is generally accepted as one of the most suitable methods for simultaneous and multielemental determination of trace amounts of elements. In this work polluted surface waters were investigated by NAA using Tsing Hua Open-pool Reactor (THOR).     

Determination of chlorine in silicate rocks by neutron activation analysis

A simple radiochemical neutron activation analysis scheme has been developed for the determination of chlorine in silicate rocks. The method involves a 15-min thermal neutron irradiation of rock powder followed by a quick separation of ³⁸Cl as AgCl, and Ge(Li) spectrometry. Chemical yield, normally ranging between 95% and 100%, is monitored gravimetrically through the recovery of AgCl. The procedure has been tested on several geochemical standards to assess its accuracy and precision. The values obtained for standard rocks agree with the literature values. At the 100-ppm level, the analytical precision for chlorine is within ±5% (2σ).     

The determination of bromine in rocks by neutron activation analysis

A neutron activation method for the determination of bromine in rocks and minerals is described. After removal of iodine, bromine is separated by oxidation with potassium permanganate and extraction with carbon tetrachloride. Bromine is thon precipitated as silver bromide; yields are from 60 to 84%. The method has a sensitivity of 0.001 p.p.m. of bromine and is free from interfering reactions. The values obtained for G-1 and W-1, 0.484 and 0.490 p.p.m. of bromine respectively, are lower than the average values for granites and basalts previously reported.     

Precision analyses of manganese in rocks by neutron activation analysis

A simple and rapid procedure for the determination of manganese in rocks by neutron activation and γ-spectrometry is presented. The precision of the method calculated from analyses of standard rocks is of the order 1.5–2%, and an accuracy of ±2% is attainable. The method is applicable to most types of geological samples, and should be superior to conventional methods used in rock analysis.     

Interference in neutron activation analysis of rocks by uranium fission

Interferences by uranium fission for⁹⁵Zr,⁹⁹Mo,¹⁰³Ru,¹⁴⁰La,¹⁴¹Ce and¹⁴⁷Nd have been studied using a single comparator method with two monitors. The effect of the neutron energy spectrum on the interference factor was examined by using the effective activation cross section. All the activities of¹⁴⁰La produced during neutron irradiation of uranium were included in the calculation of the factor for lanthanum. The calculated and experimental interference factors are in good agreement within 10% deviation. The results have been applied for the analysis of several rock samples containing uranium in a wide concentration range.     

Preconcentration of trace manganese from natural waters by complexation with dithiocarbamate and adsorption onto C18-solid phase extraction column for neutron activation analysis

A method was developed for the preconcentration and separation of trace manganese from natural water samples by complexation with dithiocarbamate followed by adsorption onto C₁₈-solid phase extraction column prior to irradiation. The Mn recovery was better than 99.8% without inteference from iron(III) at 5 mg^.l^-1, copper(II), zinc(II), aluminum(III) and cobalt(II) at 0.5 mg^.l^-1 and sodium(I), potassium(I), magnesium(II) and calcium(II) at 1 mg^.l^-1. The separation factor was 100 and the detection limit was 0.01 μg^.l^-1 with good precision and accuracy with a relative error lower than 3%. The method was applied to the determination of Mn in tap, well, river and treated water samples. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of the silver content of ancient silver coins by neutron activation analysis

A reactor neutron activation analysis procedure for the determination of the silver content of silver coins is described. The samples are irradiated for 1 s, cooled for 85 s and measured for 60 s with a Ge-detector. The analysis is based on the measurement of¹¹⁰Ag and¹⁰⁸Ag. Aluminium is used for flux monitoring and pulse pile-up correction. A calibration curve is prepared by irradiating and measureing a series of discs with known silver contents. An average precision of ±2.1% is obtained. The analysis of coins with known silver contents shows good agreement with the given values. The analysis time is 2.5 minutes per sample.     

Non-destructive examination of roman silver coins by neutron activation analysis

The detection of “plated” specimens (ancient falsifications consisting of a copper core with a silver outer layer) amidst a great collection of silver coins was performed by non-destructive neutron analysis. The “plating” can be detected by measuring the Ag/Cu ratio. In practice it is more convenient to determine the Au/Cu ratio which is proportional to it, A short activation in a low thermal neutron flux is sufficient for this purpose. Consequently the induced activity of the long-lived^110mAg is small. The necessary correction for self-absorption on the measured ratio is small. A series of 2000 coins was analysed in this way.     

Determination of silver traces in air by neutron activation analysis

A non-destructive system for determination of silver traces in air particulates collected on cellulose filters is described, based on neutron activation followed by¹¹⁰Ag β⁻ counting instead of the 657.7 keV γ-ray. The determination limit (for 10% confidence limit) is estimated to be about 10⁻⁹ g. The method is easily applicable to the determination of silver in cloud seeding experiments, since the filters themselves provide a consistent and fairly uniform source and samples are collected in general far from industrial areas, where the concentration of possible interfering elements in air is reasonably low.