Chemical modification of silica surface by immobilization of functional groups for extractive concentration of metal ions

Increased utilization of mechanically stable synthetic matrices particularly silica gel as a solid support and its surface modification either by impregnation of organic ligands directly or covalent grafting through spacer unit for extractive concentration of trace elements are highlighted in the present article. Experimental evidences for existence of surface silanol and its chemical nature have explored the idea of silica surface modification. Recent methods of development in functionalized silica synthesis by attachment of various ligands or organic reagents to the silica surface and techniques of characterization of the modified surface have been reported. Analytical applications of various modified silica surfaces, in particular, adsorption of trace elements taking separation and preconcentration into account from complex synthetic mixture as well as natural water is presented.     

A provenance study of coffee by photon activation analysis

Photon activation analysis (PAA) is a multi-elemental radioanalytical technique in trace elements analysis with high accuracy and precision. Researchers at the Idaho accelerator center performed PAA analysis on coffee samples from several locations around the world as an initial step in assessing the relationship between trace elements in illicit drugs and the soils in which they were grown. The preliminary results show coffees from different locations have different concentrations of trace elements. In the three cases where we have soil samples, the matrices of elements in the coffee samples are closely related to the matrices of the elements of the local soil samples. The majority of trace elemental content is similar to that of the local soil sample in which the coffee is planted. It may be that coffee assimilates numerous elements from the soil where it is grown in similar ratios as is found in the soil. Thus, it is conceivable that the elemental content could serve as “fingerprint” to trace the origins of the coffee. To verify our analytical results we applied X-ray fluorescence (XRF) methods as well. Our PAA results are consistent with XRF experimental data. The future of tracing the origin of illicit drugs with the PAA technique is promising.     

High-resolution spectra of selected rare earth elements and spectral interferences studied by inductively coupled plasma-atomic emission spectroscopy (ICP-AES)

The rare earth elements (REEs) play very important roles in industrial manufacturing, technology development and biological processes. Due to their complex emission spectra, trace levels of REEs are difficult to analyze by conventional ICP-AES techniques. The present study investigates possible spectral interferences of matrices (rare earth oxides of Ce, Pr, Nd, Sm and Dy) on the analytical lines (± 0.1 nm) of a target REE. Detailed and well-resolved spectra for selected REEs are presented, and procedures used to rectify the problem of spectral interferences caused by REE matrices are discussed. A computer-assisted system (CAS) for spectral recognition has been developed and used to assist in the study of matrix interference. To determine directly trace rare earth elements in REE matrices without sample pre-separation, the application potential is demonstrated with a one meter sequential instrument retrofitted with a 3600 grooves/mm grating.     

Comparative evaluation of the possibilities of INAA, ED-XRF, ICP-AES and AAS in the analysis of plants

The usefulness of INAA, radionuclide ED-XRF, ICP-AES and AAS are comparatively evaluated for the determination of nutrients, essential and trace elements in various plant matrices. The comparison is performed by analysis of the following reference materials: NIST-SRM-1573, NIST-SRM-1575, NIES-1, NIES-3, NIES-6, IAEA-V-10 and Bowen's kale. The detection limits, accuracy and precision of the methods are discussed and a combination of INAA and GFAAS is recommended for analysis of plants for monitoring purposes.     

光谱分析新光源的完善及发射光谱仪的改造

设计了一种高能火花光源,并用该光源在具有较低电离电位基体中分析有较高激发线的杂质,如ZrO2中Hf;Nb2O5中Ta和MoO3中W,分析灵敏度提高了约10倍。用在较长波段分析气体杂质（如O和C）也是可能的。     

Speciation problems solved with NAA: Some actual cases for Hg,V, Cr,As and Se

The evaluation of the eco-toxic consequences of heavy metals on the biosphere requires assessment of their biological effects. This involves the determination of the different ionic species and the various chemical forms of each element. For many elements, the usual electrochemical methods for the analysis of different chemical species do not meet the required sensitivity; ppm or even ppb concentration ranges represent often the actual content of many matrices. For many elements as Hg, V, Cr, As, and Se one of the most sensitive method of trace determinations down to the ppb level is the NAA. Unfortunately this method gives information only on the total number of nuclei present, regardless to their outer structure and chemical forms. In this work, some examples are given of the feasibility of NAA to the determination of trace amounts of different chemical species of some heavy metals, when coupled to specific separation procedures.     

Determination of trace impurities in uranium, thorium and plutonium matrices by solvent extraction and inductively coupled plasma atomic emission spectrometry

Studies on the determination of trace metallic impurities in nuclear materials such as uranium, thorium and plutonium are described. The bulk of the matrix is separated by batch extraction from their nitric acid solutions using 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate (KSM-17, equivalent to PC88-A). The final aqueous phase containing the metallic impurities is fed to a high-temperature source inductively coupled plasma and the analysis is carried out employing a computer-controlled multichannel direct-reading spectrometer. The studies also included the recovery of impurities at various acidities and spectral interferences of the above matrices over the analyte elements. Based on the above studies, methods were standardized for the determination of 19 elements, viz. Al, B, Be, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Si, Zn, Ce, Dy, Eu, Gd and Sm, in U/Th/Pu solutions. The relative standard deviation for various elements is in the range 1-5%.     

Determination of trace elements and correction of mass spectral interferences in superalloy analyzed by glow discharge mass spectrometry

Mass spectral interference was investigated systematically during the determination of trace elements in superalloy by glow discharge mass spectrometry (GD-MS); moreover the main mass spectral interference and interference level of isotopes were provided in detail. According to the mass spectral interference of elements, different methods were selected for interference correction. The effects of mass spectral interference were removed efficiently by using correction methods such as selecting isotopes without interference, matching sample matrices and deducing interference with multivariable linear regression. The determination results of three superalloy samples show that trace elements such as B, Mg, Ga, As, Ag, In, Sn, Sb, Te, Tl, Pb and Bi were determined successfully after interference correction.     

Microwave-induced plasma coupled to a tantalum-strip vaporization assembly for trace element analysis

This report describes a tantalum-strip assembly coupled to a microwave-induced plasma. Detection limits obtained for several elements by using the apparatus are given. A procedure using bomb decomposition and chelate extraction in conjunction with the tantalum-strip assembly/microwave-induced plasma system for the determination of trace elements in samples with complex matrices is also described. Recoveries from spiked standards are given.     

Simultaneous multi-element analysis of trace elements in soil samples by means of high-resolution inductively coupled plasma sector field mass spectrometry (SF-ICP-MS)

The potential of SF-ICP-MS for trace element analysis in complex environmental matrices such as soil solutions was investigated. Spectral interferences found in mass spectra of soil matrices are presented in detail. Furthermore, the influences of single components of the soil matrix on the signal intensity of selected elements were studied. Detection limits of different elements are presented with respect to the composition of the matrix. A fast and accurate method for quasi-simultaneous determination of Al, Si, P, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Se, Sr, Mo, Cd, Sn, Hg and Pb in aqueous soil extracts was established.     

Inequalities for fermion density matrices

A partial trace over the occupation numbers of all but k states in the density matrix of an ensemble with an arbitrary number of single-particle states is defined as the (reduced) k-state density matrix. This matrix is used to obtain a complete, practical solution to the problem of determining the representability of the diagonal elements of the one- and two-particle (reduced) density matrices. This solution is expressed as a series of linear inequalities involving the density-matrix elements; the inequalities are identical with those derived previously by Davidson and McCrae by a different method. In addition, our method is used to obtain nonlinear, matrix inequalities on the off-diagonal elements of the density matrices.     

Preliminary homogeneity study of in-house reference material using neutron activation analysis and X-ray fluorescence

Summary Although many biological reference materials for quality control of trace element analysis are commercially available, there is still a need for additional local materials for special matrices. In the Latin American region a preliminary study has been commenced involving analytical strategies for the characterization of in-house reference material. A biological sample, prepared in Brazil, constitutes the first regional attempt to prepare reference material. It was analyzed by neutron activation analysis (NAA) and X-ray fluorescence (XRF) to verify its homogeneity. The determination of the trace elements and certain major elements was carried out by instrumental NAA. Trace elements such as Cd, Mn, Mo and Cu were determined using NAA with radiochemical separations to improve the sensitivity and precision. XRF was applied only to major constituents and some trace elements with concentration of more than 10 g/g. From a total of 18 elements analyzed, only Fe, Cr and Sc were not homogeneously distributed.     

Recent trends in total reflection X-ray fluorescence spectrometry for biological applications

This review is focused on the application of total reflection X-ray fluorescence (TXRF) spectrometry in the field of biological research. In the last decade, most papers were published by authors who applied laboratory-scale TXRF equipments. The application of synchrotron radiation as excitation source (SR-TXRF) shows a slowly increasing tendency. In the cited papers the micro-, trace and multielement capability of these TXRF techniques was demonstrated in the clinical and medical laboratory practice, as well as in various plant physiological studies. For speciation of elements in biological matrices, the TXRF was used as element specific detector following an off-line separation step (e.g., thin layer chromatography, high performance liquid chromatography), however, these off-line methods are not competitive with the on-line coupled HPLC-inductively coupled plasma mass spectrometry.     

Simultaneous multi-element analysis of trace elements in soil samples by means of high-resolution inductively coupled plasma sector field mass spectrometry (SF-ICP-MS)

The potential of SF-ICP-MS for trace element analysis in complex environmental matrices such as soil solutions was investigated. Spectral interferences found in mass spectra of soil matrices are presented in detail. Furthermore, the influences of single components of the soil matrix on the signal intensity of selected elements were studied. Detection limits of different elements are presented with respect to the composition of the matrix. A fast and accurate method for quasi-simultaneous determination of Al, Si, P, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Se, Sr, Mo, Cd, Sn, Hg and Pb in aqueous soil extracts was established. Received: 3 January 2000 / Revised: 28 March 2000 / Accepted: 31 March 2000     

Utilization of pneumatic carrier facility of Dhruva reactor for trace element determination by neutron activation analysis

The pneumatic carrier facility (PCF) of Dhruva reactor is being extensively used for neutron activation analysis (NAA) studies pertaining to research work as well as routine sample analysis. It is useful for the determination of trace elements using short and medium half-lives radioisotopes produced in neutron activation with available higher neutron flux (~5 × 10¹³ cm^?1 s^?1). Solid samples placed in high density polypropylene capsule, are irradiated for 1 min duration and radioactive assay is carried out by high resolution gamma ray spectrometry. Design aspects of PCF and various applications to samples of diverse matrices using NAA are presented.     

Determination of trace elements in biological fluids

Main approaches to the trace element analysis of biological fluids and problems appearing in this case are considered. The specific character of these approaches is illustrated by the examples of the analysis of real samples for various trace elements. The advantage of methods for the direct determination of trace elements in these samples is demonstrated.     

Trace element characterization by INAA of three sediments to be certified as standard reference materials

Three environmental matrices proposed as Certified Reference Materials, issued by the EU Standards, Measurement and Testing Programme (SMTP) formerly Bureau Communautaire de Reference (BCR) have been characterized for their trace element contents.The materials are: BCR 277 R Estuarine Sediment, BCR 280 R Lake Sediment and BCR 320 R Channel Sediment.Several trace elements, including As, Co, Cr, Fe, Mn, Ni, Sb, Sc, Th, U and Zn have been determined by our laboratory using Instrumental Neutron Activation Analysis (INAA). Our contributed values are being considered for the final certification.     

Laser-excited atomic-fluorescence spectrometry with electrothermal tube atomization

The performance of graphite-tube electrothermal atomizers is evaluated for laser-excited atomic-fluorescence spectrometry for several elements. Three pulsed laser systems are used to pump tunable dye lasers which subsequently are used to excite Pb, Ga, In, Fe, Ir, and Tl atoms in the hot graphite tube. The dye laser systems used are pumped by nitrogen, copper vapour and Nd:YAG lasers. Detection limits in the femtogram and subfemtogram range are typically obtained for all elements. A commercial graphite-tube furnace is important for the successful utilization of the laser-based method when the determination of trace elements is intended, especially when complicated matrices may be present.     

Study on chemical species of inorganic elements in some marine algae by neutron activation analysis combined with chemical and biochemical separation techniques

The compositional changes of inorganic elements on freshwater leaching of 35 species of Chinese algae were studied by the determination of the element contents in marine algae using instrumental neutron activation analysis. It was found that alkali metals and chlorine mainly exist as ions in algae, in which, water-soluble K and Na exist as chlorides. While, other elements exist as the states of both ions and organic combination in which the water leaching ratios of alkaline earth metals are the lowest. The combination of trace elements with various organic macromolecules inSargassum kjellmanianum was also studied using neutron activation analysis combined with chemical and biochemical separation techniques. The results indicate that the concentration of many trace elements, such as Zn, Fe, Sc, Th are earths in protein are quite high, and some trace elements can also be combined by pigment and polyphenol. Alkaline earth metal mainly bind with alginic acid inSargassum kjellmanianum.