Neutron activation analysis of the NIST Bovine Serum Standard Reference Material using chemical separations

Summary The US National Institute of Standards and Technology is currently in the process of certifying a Bovine Serum Standard Reference Material. In addition to elements normally considered to be of clinical interest, a number of other elements, which are analytically more difficult to determine yet are of importance from either a nutritional or toxicological viewpoint, are being determined by a variety of analytical techniques. Neutron activation analysis in combination with appropriate pre- or post-irradiation chemical separations, has been used to determine many of these difficult elements.

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Neutronenaktivierungsanalyse des Standardreferenzmaterials NIST Bovine Serum mit Hilfe chemischer Trennungen

     

Template-synthesized nanotubes for chemical separations and analysis

We have developed a new class of synthetic membranes that consist of a porous polymeric support that contains an ensemble of gold nanotubes that span the thickness of the support membrane. The support is a commercially-available microporous polycarbonate filter with cylindrical nanoscopic pores. The gold nanotubes are prepared by electroless deposition of Au onto the pore walls, that is, the pores acts as templates for the nanotubes. We have shown that by controlling the Au deposition time, Au nanotubes that have effective inside diameters of molecular dimensions (<1 nm) can be prepared. These nanotube membranes can be used to cleanly separate small molecules on the basis of molecular size. Furthermore, use of these membranes as a novel electrochemical sensor is also discussed. This new sensing scheme involves applying a constant potential across the Au nanotube membrane and measuring the drop in the transmembrane current upon the addition of the analyte. This paper reviews our recent progress on size-based based transport selectivity and sensor applications in this new class of membranes.     

Single-step radiochemical separations by column procedures in activation analysis

Some single-step column procedures are described for both individual and group activity separations. Besides the usual ion-exchange techniques, other methods such as reverse-phase chromatography, isotopic exchange and the use of resins converted into special forms were used. Fast and simple selective separations from 2N hydrochloric acid are reported for Mo(VI), Cu(II), Sb(V), and for AsO₄^3- + PO₄^3- from both 2 N hydrochloric acid and I N sulfuric acid; for Cu, Sb and As + P, the selectivity can be greatly increased by using a guard bed of resin in normal form. By combining the different techniques a single-step separation scheme for 6 elements (Mo, Au, Zn, As, Cu, Sb) in 2 N hydrochloric acid was developed; this allows high chemical recoveries, high cross-decontamination and very large decontamination from ²⁴Na to be reached, so that application for biological sample analysis can be envisaged. Simplified two-stage column separations for Au + Sb and Cu and Fe + Sb and Zn from concentrated hydrochloric acid (cationic and anionic resin beds coupled) are also reported.     

Improving accuracy in routine instrumental activation analysis

An INAA procedure for routine analysis of rock samples is described. Samples are irradiated using a rotating sample holder. Measurement of the induced gamma activity is performed using an automatic gamma spectrometer and the elemental concentrations are calculated by a computer. The analytical error is discussed and the precision and accuracy evaluated experimentally. An average error of ±3–5% without considering counting statistics is obtained. Results for 19 elements in 8 international standard rocks are reported. A short discussion of the cost of the analysis is included.     

Automated and routine liquid chromatographic analysis of antiepileptic drugs

We describe an optimized automated liquid chromatographic method for simultaneous measurement of primidone, phenobarbitone, phenytoin, carbamazepine and clonazepam. A Waters Tri-Module automation system is used and it provides direct read-out of results after chromatography. A one-step extraction with ethyl acetate is used to extract the drugs from 100 microL serum samples. We use an isocratic mobile phase and monitor the column effluent at 210 nm. Drug levels as low as 5 mumol/L can be detected. The within-run CV's range from 1.4 to 2.7%, and the between-run CV's range from 5.2 to 6.1%. Analytical recovery is in the range from 94-108%. The method compares favourably with the enzyme multiple immunoassay technique for routine antiepileptic drugs monitoring, in accuracy, efficiency and cost-effectiveness.     

Multielement standards in routine reactor neutron activation analysis

The application of multielement standards (MES) in routine neutron activation analysis brings a whole range of advantages. This paper deals with the experience obtained during many years of application of these MES. Nine of these MES contain a total of 50 elements in suitable combinations and concentrations; thus, the determination of most of the common elements by NAA can be carried out simultaneously. This refers to the following elements: Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Mo, Ag, Cd, In, Sb, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, W, Re, Au, Hg, Th and U. For the determination of the remaining elements such as Zr, Ta, Ir etc., single element standards (SES) are used.     

Rapid radiochemical separations in neutron activation analysis using ion retention media

A rapid radiochemical procedure based on the removal of mercury, selenium, arsenic and antimony by columns of C₁₈-bonded silica gel or activated carbon after their selective complexation in sulphate/nitrate media by ammonium pyrrolidine-dithiocarbamate, diethylammonium diethyldithiocarbamate, potassium ethyl xanthate, bismuthiol II or 8-hydroxyquinoline, was examined. Comparisons were made of the ability of the two ion retention media to remove these metal ions and to allow their regeneration and recycling. The effectiveness of this technique was demonstrated by analysis of horse kidney and human diet, International Atomic Energy Agency biological reference materials, for mercury and selenium.     

Continuous gas phase chemical separations

Gas-phase chemical separations have been used for the study of short-lived fission products. Often the chemical separation is achieved in a few seconds. The articles reviews the techniques used in fast, gas-phase separations.     

Application of resorcinarene derivatives in chemical separations

The applications of resorcinarene derivatives in modern separation techniques including high performance liquid chromatography (HPLC), gas chromatography (GC), capillary electrophoresis (CE), ion chromatrography (IC), and liquid membranes are reviewed in this paper. Resorcinarenes are macrocyclic compounds which can be modified with various substituents on upper and lower rims to provide specific functionality and selectivity. The derivatives can be adsorbed or covalently bound to the stationary phase of HPLC, GC, and IC, or used as pseudo-stationary phase in CE to separate organic or inorganic species. They have been tested as carriers to selectively transfer species from source phase to receiving phase in bulk liquid membranes, supported liquid membranes, and polymer inclusion membranes. These broad applications of resorcinarene-based macrocyclic ligands indicate that they are a promising class of compounds that are worthwhile to be explored in both synthesis and separation applications.     

Rapid chemical separations for thermal neutron activation analysis of niobium and vanadium and application to controlled thermonuclear reactor materials studies

Interfering reactions in photon activation analysis are compiled and evaluated quantitatively; the results are based on experimentally obtained data exclusively. All elements in the Periodic Table with few exceptions have been irradiated several times with 30 MeV bremsstrahlung produced by a linear electron accelerator. The element samples were measured many times to detect all expected radionuclides and hence all possible interfering reactions. These reactions are listed and presented in Table 1.     

Automated screening platform with isochronal-parallel analysis and conditioning for rapid method development of chiral separations

An automated chiral separation-screening platform was developed, allowing separation analysis on one column while another column is simultaneously equilibrated with a different mobile phase (MP). The platform can be set up from usual HPLC components at moderate cost and it considerably speeds up the screening process, allowing numerous chromatographic conditions to be tested within a short period of time and leading to a significant gain in time and productivity in preparative separations.     

Time optimization for routine separations,using high-speed microbore HPLC

Summary Algorithms for the time optimization of an HPLC separation are presented. Resolution, column performance, extra-column variance, capacity factor, and column length are incorporated into these algorithms. Extracolumn variance for a high-speed microbore system (1 mm i. d. column) was assessed using 2nd moment variance and a non-linear extrapolation of tubing length to zero. Extra-column variance, as a function of flowrate, was incorporated into the reduced operating curve of column performance. The use of empirical correction factors for column reproducibility and homogeneity are suggested. Cutting to an optimum length did not degrade column performance. These algorithms were applied to the optimization of a microbore assay for theophylline, in a simple xanthine mixture. Resulting total analysis times were reduced to 10seconds per sample, at a flowrate of 700l/min.     

Electrochemical interfaces for chemical and biomolecular separations

The design of molecularly selective interfaces can lead to efficient electrochemically-mediated separation processes. The fast growing development of electroactive materials has resulted in new electroresponsive adsorbents and membranes, with enhanced selectivity, higher uptake capacities, and improved energy performance. Here, we review progress on the interfacial design for electrochemical separations, with a focus on chemical and biological applications. We discuss the development of new electrode materials and the underlying mechanisms for selective molecular binding, highlighting areas of growing interest such as metal recovery, waste recycling, gas purification, and protein separations. Finally, we emphasize the need for integration between molecular level interface design and electrochemical engineering for the development of more efficient separation processes. We envision that electrochemical separations can play a key role towards the electrification of the chemical industry and contribute towards new approaches for process intensification.     

Neutron activation analysis for the routine clinical investigation of osteoporosis

Neutron activation analysis provides a useful clinical test to assess bone mass status in vivo. The neutron flux is obtained from Pu/Be sources and⁴⁹Ca activity is measured by NaI detectors. For diagnostic value, the⁴⁹Ca measurement is related to the mean value for normal subjects of the same body size. This normalized index, our CaBI, is used extensively to diagnose the bone loss associated with osteoporosis and to asses changes in bone mass with progression of disease and in response to treatments. Our facility operates at maximum capacity (35 tests/wk.). The hospital location and the dependability and ease of operation (provided by neutron sources) have facilitated extensive clinical use.     

Molecular activation analysis for chemical species studies

Molecular activation analysis (MAA) refers to an activation analysis method that is able to provide information on the chemical species of elements in systems of interest, though its exact definition has yet to be assigned. Its development is strongly stimulated by the urgent need to know the chemical species of elements, because knowledge of bulk contents or concentrations is often insufficient to judge biological, environmental or geochemical effects of elements. The features, methodology and limitations of MAA are outlined, as well as the up-to-date MAA progress in our laboratory. Received: 14 August 1998 / Revised: 30 November 1998 / Accepted: 1 December 1998     

Reactor-detector calibration for routine instrumental neutron activation analysis of geological materials

A reactor-detector combination has been calibrated for routine determination of trace elements by instrumental neutron activation analysis using the semi-absolute method with flux corrections. The reproducibility of the calibration constants is studied using the standard rock AGV-1 for the activities¹⁴⁰La,¹⁴¹Ce,¹⁵³Sm,¹⁶⁰Tb,¹⁵²Eu,¹⁷⁵Yb,¹⁷⁷Lu,¹³¹Ba,⁶⁰Co,⁵¹Cr,¹³⁴Cs,¹⁸¹Hf,²³³Pa,⁴⁶Sc, and¹⁸²Ta. The results show that a calibration reproducibility with a relative precision of better than 5% can be achieved in many of the cases without any special precautions. To study the applicability of the calibration constants, concentrations of the corresponding elements have been determined in standard rocks, G-2, W-1 and GSP-1 and are compared with the recommended values.     

Open access atmospheric pressure chemical ionization Mass spectrometry for routine sample analysis

We report the introduction and use of an atmospheric pressure chemical ionization liquid chromatography-mass spectrometry instrument that has been designed specifically for use by the synthetic chemist on an open access, walk-in basis. This instrument has been configured with an easy-to-use sample log-in terminal that requires the user to provide only a sample identification number and a user name. Sample analysis takes approximately 4 min and provides the synthetic and medicinal chemist with rapid and reliable mass spectrometry analysis. Since installation of the system, it has analyzed an average of about 80 samples per day and has the capacity to run over 100 samples per day without the intervention of a specialist operator. This capability has eliminated the need for an operator to analyze routine samples and allows the mass spectroscopist more time to deal with problem solving.