Radiochemical neutron activation analysis of trace lanthanoids in geological and cosmochemical samples

In order to determine trace lanthanoids in geological and cosmochemical samples, an analytical procedure for radiochemical neutron activation analysis (RNAA) was developed, where lanthanoids are radio-chemically purified through precipitations of hydroxides and fluorides, and cation exchange using HBr as an eluent. Chemical yields are determined by reactivation. The procedure was applied to the Allende meteorite and geological standard rocks. Our data for Allende are in excellent agreement with literature values, and those values for standard rocks, JP-1 (peridotite) and JF-2 (feldspar), in which lanthanoids are depleted by orders of 1 to 2 compared with those in Allende, seem to be reasonable, although not properly evaluated because of large scatterings in their literature data. This suggests that the present RNAA procedure is highly effective in determining trace lanthanoids (less than 1 ng) in rock samples.     

Use of neutron activation analysis for the determination of cesium in Pd electrodes on Pt and Au matrices

A method of neutron activation analysis (NAA) for the determination of Cs inside a thin Pd electrode deposited on a Pt or Au matrix is reported. This simple and rapid method involves a post-irradiation radiochemical separation of Cs from high activities of interfering radionuclides. The separated Cs was determined by high resolution -ray spectrometry. The method allows the determination of Cs without a time-consuming cooling period. The radiochemical procedure (RNAA) is found to be relatively highly precise, sensitive, rapid and simple. Pre-irradiative chemical separation of Cs is likely to be reasonable.     

Column solid phase extraction and determination of ultra-trace Au,Pd and Pt in environmental and geological samples

A new sorbent based on cysteine modified silica gel (SiG-cys) was prepared and studied for preconcentration and separation of noble metals Au(III), Pd(II), Pt(II), Pt(IV). Its extraction efficiency was examined by batch and column solid phase extraction procedures. Laboratory experiments performed showed that sorbent is characterized with high selectivity, permiting quantitative sorption (93–97%) of noble metals Au, Pd and Pt from acidic media 0.1–2 mol L^? 1 HCl and unsignificant sorption (less than 2%) for common base metals like Cu, Fe, Mn and Zn. The analytes retained on the sorbent are effectively eluted with 0.1 mol L^? 1 thiourea in 0.1 mol L^? 1 HCl and measured by ETAAS or ICP OES under optimal instrumental parameters. The sorbent showed high mechanical and chemical stability and extraction efficiency was not changed after 500 cycles of sorption/desorption. The sorbent was successfully applied in analyticals procedures for preconcentration and determination of Au, Pd and Pt in geological and soil samples. Detection limits (3σ criteria) achieved, depending on the instrumental methods used are: ETAAS (0.005 μg L^? 1 for Au in river and sea water, 0.002 μg g^? 1 for Au in copper ore and copper concentrate); ICP OES (0.03 μg L^? 1 for Pd and 0.06 μg L^? 1 for Pt in river and sea water, 0.006 μg g^? 1 for Pd in copper ore and copper concentrate and 0.002 μg g^? 1 for soluble Pt in soil). The accuracy of the procedures developed was confirmed by added/found method for sea and river water; by the analysis of national certified materials (copper ore and copper concentrate for Au and Pd) and by determination of the sum of soluble Pt(II) + Pt(IV) in spiked soil samples.     

Radiochemical neutron activation analysis determination of rare earth elements in geological materials with ppb sensitivity

Rare earth elements are determined, with ppb sensitivity, by radiochemical activation analysis using a fusion dissolution process and a quantitative group separation scheme, followed by radioassaying. Spectral interference is avoided, or corrected for, by repeating the counting operation with a delay of four to six weeks. This allows for the decay of shorter lived interfering isotopes such as¹⁵⁵Eu on¹⁶⁰Tb and¹⁷⁵Yb on¹⁴¹Ce. The scheme is rapid, sensitive and uses standard radiochemical laboratory facilities and counters. It has been applied to a wide range of rocks and minerals and data for eleven rare earths (La, Ce, Nd, Sm, Eu, Gd, Tb, Ho, Tm, Yb and Lu) is presented here and compared with literature values.     

TNA负载聚氨酯泡塑富集ICP-MS测定地球化学样品中痕量金、铂、钯

研究提出了负载聚氨酯泡沫塑料富集ICP—MS测定地球化学样品中的金、铂、钯的方法,研究了样品经灼烧、王水溶样后,负载泡沫塑料吸附条件、干扰的消除、仪器的最佳化、内标元素的选择等。在本工作的实验条件下获得的方法检出限分别为Au：0．12ng／g,Pt：0．10ng／g,Pd：0．08ng／g。本法测定了国家一级地球化学标准物质中的痕量Au,Pt,Pd,测定值与标准值相吻合。     

Fast and precise determination of fluorine in geological samples by 14 MeV neutron activation analysis

A fast and precise method of determining fluorine in geological matrices is proposed. The 0.20 MeV photopeak of¹⁹O, induced by the¹⁹F(n, p)¹⁹O reaction, was used for this assay. Neutron flux monitoring was achieved by adding an internal standard monitor (20 mg Ce) to each sample and counting the activity due to the 0.74 MeV photopeak of^139m Ce, produced in the¹⁴⁰Ce(n, 2n)^139m Ce reaction. This activity was considered to be proportional to the neutron flux during the sample irradiation. This method of fluorine determination was checked on two fluorine geological standards, mica and apatite, containing 1.50 and 2.90% fluorine, respectively. The sensitivity of the method, obviously depending upon the matrix composition, was 1.46 mg for the mica standard.     

Radiochemical neutron activation analysis of Cs and Rb in geological samples using zeolite (clinoptilolite) chromatography and sodium tetraphenylborate precipitation

Three procedures for separating of Cs and Rb from geological samples were investigated. The fractional recovery was determined by radioactive tracers and by RNAA. In the first procedure 0.2 g of irrdiated sample is fused with Na₂O₂, acidified and passed through a clinoptilolite zeolite column. Cs and Rb were eluted with 7.5M HNO₃; chemical yields are in the range 93–98%. The second procedure is a supplement to the SUNDBERG and BOYNTON (1976) procedure; a previously discarded anion-exchanger effluent, containing Cs, Rb, Co, Na, etc., is passed through a clinoptilolite column. Cs and Rb are eluted with 7.5M HNO₃; yields are in the range of 82–94%. A third separation involves precipitation of Cs and Rb from the effluent and washings with sodium tetraphenylborate (NaBPh₄); yields are 64–83%.     

Radiochemical multielement neutron activation analysis of tungsten

A radiochemical neutron activation technique for the detemination of 19 elements in high purity tungsten has been developed. It is based on extraction with diantipyrylmethane (for tantalum and antimony), substoichiometric extraction of molybdophosphate (for phosphorus) and anion-exchange chromatography (other elements) in hydrofluoric acid medium. The results obtained and achievable limits of detection are given. The effects of self-shielding and nuclear interfering reactions are discussed.     

Synthesis of Au, Au/Ag, Au/Pt and Au/Pd nanoparticles using the microwave-polyol method

Gold, Au/Ag, Au/Pt and Au/Pd bimetallic nanoparticles with varying mol fractions were synthesized in ethylene glycol and glycerol, using the microwave technique in the presence of a stabilizer poly(N-vinylpyrrolidone) (PVP). It was found that bimetallic colloids of Au/Ag, Au/Pd and Au/Pt form an alloy either on co-reduction of respective metal ions or on mixing individual sols.     

Determination of rare earths in geological samples by neutron activation analysis

The significance of rare earth distribution patterns in trace element geochemistry is briefly reviewed. Established methods for their determination at the Reactor Centre by instrumental and radiochemical techniques are described, and examples of recent applications discussed.     

Pt and Au analysis by delayed X-ray spectrometry after fast neutron activation

A novel technique for the determination of Pt and Au at low concentrations is described. The method involves /K/ X-ray spectrometry preceded by fast neutron activation of the stable isotopes of the elements of interest. A full appraisal of the technique is presented for the analysis of small powdered samples. The sensitivity was optimized by employing a detector that was particularly effective at energies below 150 keV. The investigation formed the basis of a feasibility study which was utilized to establish if the application could be developed for the routine off-line determination of Pt and Au. We show that the method does not necessarily depend on the sample matrix, and that it proves to be a strong rival to conventional activation analysis.     

Radiochemical neutron activation analysis of individual rare earth elements in monazites from different geological environments

Radiochemical neutron activation analysis /RNAA/ has been applied for the determination of individual rare earth elements /REE/, except Tm, in 8 Indian monazites and one each from Malaysia and Thailand. Because of the very low amounts of heavy rare earths /HREE/ compared to light rare earths /LREE/ in monazite, HREE from Ho onwards have been determined only after the separation of the heavy and light rare earth fractions in the irradiated monazite samples. The results indicate significant variations in REE contents from Eu to Lu among different monazite samples. The chondritic normalized REE patterns of all the samples show a prominent negative Eu anomaly with different slopes at the heavy rare earth end. All the individual REE, except Tm, have been reported for the first time in various Indian monazites.     

Instrumental neutron activation analysis for multi-elemental determination in Indian tea samples

Instrumental neutron activation analysis (INAA) was employed to determine concentrations of 19 elements (As, Ba, Br, Ce, Co, Cr, Cs, Fe, K, La, Mn, Na, Nd, Rb, Sc, Sm, Th, Yb and Zn) in a large number (55) of tea samples (from market as well as virgin tea leaves) from different locations in India (Assam, Darjeeling, Munnar and Kangra). The results obtained in the present work are compared with those reported in literature. The concentration levels, their variations with collection locations and the correlations among different elements in these samples are discussed.     

Prompt gamma-ray neutron activation analysis for multi-element determination in sediment samples

A facility for the irradiation of internal targets has been installed at the research reactor FRG-of the GKSS Research Center. Thermal-neutron induced prompt gamma radiation was detected by pair spectrometer. With this experimental arrangement concentrations of the major and mino elements Na, Al, Si, K, Ca, Ti, Mn, Fe, Zn, Cl, and S, as well as of the trace constituents Cr Ni, Cu Cd, and Hg of samples from a sediment core of the Elbe River could be determined. The results indicate, that prompt gamma-ray neutron activation analysis (PGNAA) is a powerful instrumental tool for a complete characterization of the main sediment constituents and for the detection of the trace elements Cd and Hg which are of considerable ecological relevance.     

Radiochemical neutron activation determination of phosphorus in high pure germanium

A radiochemical procedure for determination of ultra low concentrations of phosphorus in germanium has been developed. The method involves application of multicells autoclaves for matrix distillation and extraction chromatography with dioctyltin diacetate for final phosphorus purification. The detection limit is 40 ppt for a 1-g sample.     

Synthesis of Pt, Pd, Pt/Ag and Pd/Ag nanoparticles by microwave-polyol method

Pt, Pd, Pt-Ag and Pd-Ag bimetallic nanoparticles were synthesized in ethylene glycol and glycerol using the microwave technique in the presence of a stabilizer poly(N-vinylpyrrolidone) (PVP). It has been observed that PVP is capable of complexing and stabilizing nanoparticles. Mixed clusters were formed by simultaneous reduction of the metal ions. The clusters were characterized using UV-Vis spectra, XRD and dynamic light scattering. To understand the mechanism of formation of mixed nanoparticles, several experimental parameters such asin situ irradiation of mixed metal salts and mixing of individual sols were attempted.     

Determination of 22 elements in geological samples by instrumental neutron activation analysis

An instrumental neutron activation analysis (INAA) method has been developed for multi-element determination in geological samples. The INAA method consists of irradiation of samples for 90 sec at a flux of 1.0·10¹² n·cm⁻²·sec⁻¹ and determination of 12 elements by using their short-lived nuclides. Samples have been re-irradiated for 3 hrs for measuring concentrations of another 10 elements. Precision and accuracy of the INAA method have been evaluated by analysing samples and USGS standard reference materials. Precision and accuracy are within±15% and ±10%, respectively.