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Analytica Chimica Acta (v.688, #1)
Development of an improved method to perform single particle analysis by TIMS for nuclear safeguards by M. Kraiem; S. Richter; H. Kühn; Y. Aregbe (pp. 1-7).
This paper describes an improved method for the accurate determination of the isotopic composition in single micrometer-sized (<1μm) uranium oxide reference particles using in situ SEM micromanipulation and thermal ionization mass spectrometry (TIMS) combined with filament carburization and multiple ion counting (MIC) detection.Display Omitted▶ Accurate isotopic analysis of single sub-μm sized U particles by TIMS is performed. ▶ Filament carburization combined with MIC detection provides increased sensitivity. ▶ A baking procedure that employs a modified side filament reduces the background. ▶ Reliable measurement results are obtained also for the U minor abundant isotopes. ▶ The method is a valuable analytical tool for environmental and safeguards samples.A method is described that allows measuring the isotopic composition of small uranium oxide particles (less than 1μm in diameter) for nuclear safeguards purposes. In support to the development of reliable tools for the identification of uranium and plutonium signatures in trace amounts of nuclear materials, improvements in scanning electron microscopy (SEM) and thermal ionization mass spectrometry (TIMS) in combination with filament carburization and multiple ion counting (MIC) detection were investigated. The method that has been set up enables the analysis of single particles by a combination of analytical tools, thus yielding morphological, elemental and isotopic information. Hereby individual particles of certified reference materials (CRMs) containing uranium at femtogram levels were analysed. The results showed that the combination of techniques proposed in this work is suitable for the accurate determination of uranium isotope ratios in single particles with improved capabilities for the minor abundant isotopes.
Keywords: Uranium; Isotope ratio; Individual particles; TIMS; SEM; Nuclear safeguards
Recent developments in electrochemical flow detections—A review by Marek Trojanowicz (pp. 8-35).
This article is a review of the progress in application of electrochemical detections in liquid chromatography in recent 15–20 years. Based on 238 references, mostly to original research papers, it presents applications of amperometric and voltammetric detections, as well as coulometric, conductimetric and potentiometric ones. In case of those which have reached already the stage of routinely employed detections with commercially available instrumentation (amperometry, coulometry, conductometry) especially novel and original applications are presented. In case of voltammetric and potentiometric detections a ways of their improvements are showed, directed towards obtaining competitive results with other detection methods.
Keywords: Electrochemical detections; Liquid chromatography; Amperometric; Voltammetric; Potentiometric; Coulometric; Conductometric
A new atomization cell for trace metal determinations by tungsten coil atomic spectrometry by G.L. Donati; R.B. Wildman; B.T. Jones (pp. 36-42).
A new metallic atomization cell is used for trace metal determinations by tungsten coil atomic absorption spectrometry and tungsten coil atomic emission spectrometry. Different protecting gas mixtures are evaluated to improve atomic emission signals. Ar, N2, CO2 and He are used as solvents, and H2 and C2H2 as solutes. A H2/Ar mixture provided the best results. Parameters such as protecting gas flow rate and atomization current are also optimized. The optimal conditions are used to determine the figures of merit for both methods and the results are compared with values found in the literature. The new cell provides a better control of the radiation reaching the detector and a small, more isothermal environment around the atomizer. A more concentrated atomic cloud and a smaller background signal result in lower limits of detection using both methods. Cu (324.7nm), Cd (228.8nm) and Sn (286.3nm) determined by tungsten coil atomic absorption spectrometry presented limits of detection as low as 0.6, 0.1, and 2.2μgL−1, respectively. For Cr (425.4nm), Eu (459.4nm) and Sr (460.7nm) determined by tungsten coil atomic emission spectrometry, limits of detection of 4.5, 2.5, and 0.1μgL−1 were calculated. The method is used to determine Cu, Cd, Cr and Sr in a water standard reference material. Results for Cu, Cd and Cr presented no significant difference from reported values in a 95% confidence level. For Sr, a 113% recovery was obtained.
Keywords: Tungsten coil; Metallic cell; Atomic absorption; Atomic emission; Trace metal determination; Portability
Construction of a carbon nanocomposite electrode based on amino acids functionalized gold nanoparticles for trace electrochemical detection of mercury by Afsaneh Safavi; Elaheh Farjami (pp. 43-48).
A simple, highly sensitive and selective carbon nanocomposite electrode has been developed for the electrochemical trace determination of mercury. This mercury nanocomposite sensor was designed by incorporation of thiolated amino acids capped AuNps into the carbon ionic liquid electrode (CILE) which provides remarkably improved sensitivity and selectivity for the electrochemical stripping assay of Hg(II). Mercury ions are expected to interact with amino acids through cooperative metal–ligand interaction to form a stable complex which provides a sensitive approach for electrochemical detection of Hg(II) in the presence of other metal ions. The detection limit was found to be 2.3nM (S/N=3) that is lower than the permitted value of Hg(II) reported by the Environmental Protection Agency (EPA) limit of Hg(II) for drinkable water. The proposed nanocomposite electrode exhibits good applicability for monitoring Hg(II) in tap and waste water.
Keywords: Thiolated amino acid; Functionalized gold nanoparticles; Mercury(II); Carbon ionic liquid electrode
Horseradish peroxidase-screen printed biosensors for determination of Ochratoxin A by M. Asunción Alonso-Lomillo; Olga Domínguez-Renedo; Lorena del Torno-de Román; M. Julia Arcos-Martínez (pp. 49-53).
This work summarizes the manufacturing procedure of Horseradish peroxidase (HRP) based biosensors for the determination of the mycotoxin Ochratoxin A (OTA). The biosensors have been fabricated using the single technology of screen-printing. That is to say, an HRP containing ink has been directly screen-printed onto carbon electrodes, which offers a higher rapidity and simplicity in the manufacturing process of biosensors for OTA determination. The formal redox potential of the Fe(III/II) moiety of HRP has been used to demonstrate the effective loading of enzyme into the ink. The chronoamperometric oxidation current registered has been successfully related to the concentration of OTA in solution from different samples, including beer ones. Under the optimum conditions of the experimental variables, precision in terms of reproducibility and repeatability has been calculated in the concentration range from 23.85 to 203.28nM. A relative standard deviation for the slopes of 10% ( n=4) was obtained for reproducibility. In the case of repeatability, the biosensor retained a 30% of the initial sensitivity after the third calibration. The average capability of detection for 0.05% probabilities of false positive and negative was 26.77±3.61nM ( α=0.05 and β=0.05, n=3).
Keywords: Disposable electrodes; Screen-printed enzyme; Biosensor; Ochratoxin A
Novel determination of the total phenolic content in crude plant extracts by the use of1H NMR of the –OH spectral region by A.A. Nerantzaki; C.G. Tsiafoulis; P. Charisiadis; V.G. Kontogianni; I.P. Gerothanassis (pp. 54-60).
A novel method for the determination of the total phenolic content using1H NMR spectroscopy in the –OH spectral region is presented. The use of DMSO- d6, which is an aprotic and strongly hydrogen bonding solvent, allows the “appearance” of the relative sharp resonances of phenolic hydroxyl protons in the region of 8–14ppm. The determination of the total phenolic –OH content requires three steps: (i) a 1D1H NMR spectrum is obtained in DMSO- d6; (ii) a subsequent 1D1H NMR spectrum is recorded with irradiation of the residual water signal which results in the elimination or reduction of the phenolic –OH groups, due to proton exchange; and (iii) 1D1H NMR spectra are recorded with the addition of a progressively increased amount of salt, NaHCO3, which results in extensive linebroadening of the COOH resonances thus allowing the discrimination of the phenolic from the carboxylic acid signals. Integration, with respect to the internal standard TSP- d4, of the signal resonances between 14 and 8ppm in spectrum (i) which are either eliminated or reduced in intensity in steps (ii) and (iii) allows the quantitation of the total phenolic content. The method was applied to model compounds, a mixture of them and several extracts of natural products. The results of the proposed1H NMR method were compared to the Folin-Ciocalteu (FC) reagent method. Additionally, since1H NMR refers to the total phenolic hydroxyl protons, a reaction factor, Ae, is proposed that corresponds to the hydroxyl reactivity. The1H NMR method is rapid and accurate bearing the inherent advantages of the NMR spectroscopy and can be applied directly in complex extracts. Furthermore, it can be applied in a wide range of matrixes from crude plant extracts and food products to biological samples.
Keywords: 1; H NMR; –OH spectral region; Total phenolic content; Flavonoids; Phenolic acid; Plant extracts; Hydroxyl reactivity
On the performance of bioanalytical fluorescence correlation spectroscopy measurements in a multiparameter photon-counting microscope by Amir Mazouchi; Baoxu Liu; Abdullah Bahram; Claudiu C. Gradinaru (pp. 61-69).
Fluorescence correlation spectroscopy (FCS) data acquisition and analysis routines were developed and implemented in a home-built, multiparameter photon-counting microscope. Laser excitation conditions were investigated for two representative fluorescent probes, Rhodamine110 and enhanced green fluorescent protein (EGFP). Reliable local concentrations and diffusion constants were obtained by fitting measured FCS curves, provided that the excitation intensity did not exceed 20% of the saturation level for each fluorophore. Accurate results were obtained from FCS measurements for sample concentrations varying from pM to μM range, as well as for conditions of high background signals. These experimental constraints were found to be determined by characteristics of the detection system and by the saturation behavior of the fluorescent probes. These factors actually limit the average number of photons that can be collected from a single fluorophore passing through the detection volume. The versatility of our setup and the data analysis capabilities were tested by measuring the mobility of EGFP in the nucleus of Drosophila cells under conditions of high concentration and molecular crowding. As a bioanalytical application, we studied by FCS the binding affinity of a novel peptide-based drug to the cancer-regulating STAT3 protein and corroborated the results with fluorescence polarization analysis derived from the same photon data.
Keywords: Single-molecule fluorescence; Diffusion constant; Saturation intensity; Enhanced green fluorescent protein; Nucleus; Drosophila; Protein–ligand binding; Signal transducer and activator of transcription 3
Direct introduction of a hydrazide group into a quartz crystal microbalance surface with dodecanoic hydrazide embedded in a hybrid bilayer membrane by Saem Mun; Suk-Jung Choi (pp. 70-74).
Hydrazide group has a potential of immobilizing an antibody on a sensor surface in a way that ensures an optimal orientation and efficiency of the antibody. However, a multi-step chemical process, required for the preparation of a hydrazide group, is a barrier to its extensive application. This paper describes a new method to introduce a hydrazide group to a sensor surface by a one-step process using dodecanoic hydrazide. The method is based on an ability of the dodecanoic hydrazide to be incorporated into a hybrid bilayer membrane (HBM) layer, thereby presenting its hydrazide group to the surface. Liposome containing dodecanoic hydrazide was added to a hydrophobic self-assembled monolayer surface of a quartz crystal microbalance for the formation of a HBM. Then, the hydrazide group, presented in the surface of the HBM layer, was utilized for the oriented immobilization of an antibody via its carbohydrate moiety which was partially oxidized prior to the conjugation reaction. Activity and stable status of the incorporated dodecanoic hydrazide was revealed by the efficiency and reproducibility of the resulting immunosensor chip.
Keywords: Biosensor; Quartz crystal microbalance; Functionalization; Hybrid bilayer membrane; Hydrazide; Antibody
Tea-industry waste activated carbon, as a novel adsorbent, for separation, preconcentration and speciation of chromium by Celal Duran; Duygu Ozdes; Ali Gundogdu; Mustafa Imamoglu; Hasan Basri Senturk (pp. 75-83).
Activated carbon was produced from tea-industry wastes (TIWAC) and employed as a low cost and effective solid phase material for the separation, preconcentration and speciation of chromium species without using a complexing agent, prior to determination by flame atomic absorption spectrometry (FAAS). The characterization of TIWAC was performed by utilizing several techniques such as Fourier Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), and elemental analysis. The adsorption experiments were conducted in a batch adsorption technique. Under the experimental conditions, Cr(VI) adsorption amount was nearly equal to zero, however the adsorption percentage of Cr(III) was in the range of 95–100%. Therefore total chromium was determined after the reduction of Cr(VI) to Cr(III) and Cr(VI) was calculated by subtracting Cr(III) concentration from total chromium concentration. The suitable conditions for adsorption and speciation processes were evaluated in terms of pH, eluent type and volume, TIWAC concentration, adsorption and desorption contact time, etc. Adsorption capacity of TIWAC was found to be 61.0mgg−1. The detection limit for Cr(III) was found to be 0.27μgL−1 and the preconcentration factor was 50 for 200mL of sample volume. The procedure was applied to the determination and speciation of chromium in stream, tap and sea water. Also, the proposed method was applied to total chromium preconcentration in microwave digested tobacco and dried eggplant samples with satisfactory results. The method was validated by analyzing certified reference materials (CRM-TMDW-500 Drinking Water and CRM-SA-C Sandy Soil C) and the results were in good agreement with the certified values.
Keywords: Tea-industry waste activated carbon; Preconcentration; Chromium speciation; Batch adsorption technique; Flame atomic absorption spectrometry
An indirect competitive enzyme-linked immunosorbent assay for determination of norfloxacin in waters using a specific polyclonal antibody by Jianlan Cui; Kun Zhang; Qiuxin Huang; Yiyi Yu; Xianzhi Peng (pp. 84-89).
A specific polyclonal anti-norfloxacin antibody was obtained, and a sensitive indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed for determining trace amounts of norfloxacin in various waters. Good linearity was achieved in the range from 0.1 to 10μgL−1. The average IC50 value was determined to be 2.2μgL−1 and the limit of detection was 0.016μgL−1 at a signal-to-noise ratio of 3 in phosphate-buffered saline buffer. Recoveries of norfloxacin at various spiking levels ranged from 74 to 105% in groundwater, surface water, treated and untreated wastewater samples, with relative standard deviations of 3–5%. The assay was applied for determining norfloxacin in municipal wastewater, surface water, and groundwater collected in a metropolis of China. Raw wastewater samples were only submitted to filtration and pH adjustment while the other water samples were pre-concentrated by solid phase extraction prior to the icELISA assay. Good agreement of the results obtained by the icELISA and liquid chromatography tandem mass spectrometry further confirmed the reliability and accuracy of the icELISA for rapid detection of norfloxacin in waters.
Keywords: Norfloxacin; Polyclonal antibody; Indirect competitive enzyme-linked immunosorbent assay; Liquid chromatography tandem mass spectrometry; Water samples
Optimizing size-exclusion chromatographic conditions using a composite objective function and chemometric tools: Application to natural organic matter profiling by Regina M.B.O. Duarte; Armando C. Duarte (pp. 90-98).
A novel strategy is suggested for developing a size-exclusion chromatography (SEC) method in order to assess the molecular size distribution of natural organic matter (NOM). This strategy is based on the use of a chromatographic response function (CRF) and a response surface based on a central composite experimental design. The CRF qualifies the resolution degree attained under different SEC conditions with respect to global resolution of the chromatogram, number of distinguishable peaks, and analysis time. Based on a SEC study with a mixture of known organic compounds, predictive polynomial and linear models were developed according to the practice of design of experiments. Additionally, a chromatographic response surface was used, describing the effect of pH, amount of organic solvent, and salt concentration of the mobile phase on the values of the CRF. This new strategy predicted a single linear effect of salt concentration over the quality of the chromatographic separation, and the influence of this experimental variable on the quality of size-exclusion separations of various NOM samples was further discussed. For the analysis of NOM, the optimum settings for the mobile phase composition were as follows: pH 8.5, 11% of acetonitrile, and 15mM of sodium chloride. Under such analytical conditions, the measured molecular size distributions of water-soluble organic matter from atmospheric particles and aquatic fulvic acids compare reasonably well with the published molecular weight data. The newly developed strategy is a reliable alternative for accomplishing an accurate description of the size-exclusion profiles of NOM from different environments.
Keywords: Size-exclusion chromatography; Optimization; Chromatographic response function; Experimental design; Natural organic matter