复杂基质样品中邻苯二甲酸酯测定的样品前处理

对不同类型复杂基质样品中邻苯二甲酸酯(PAEs)测定的前处理方法进行了研究。待测样品类型包括沉积物、土壤、悬浮颗粒物、地表灰尘、生物组织、化妆品、皮革、塑料以及近岸/河口海水等复杂基质样品。这些样品中PAEs测定的最常用方法为气相色谱-质谱法(GC-MS),针对该测定方法所需的样品前处理研究集中于待测PAEs的萃取、净化等步骤操作条件的确定。对各种样品基质前处理方法的研究结果表明,二氯甲烷是进行固液萃取时最佳的超声振荡提取溶剂;而对各种复杂基质样品的净化,硅胶则是经济、实用的固相萃取填料;C18是最常用的近岸/河口海水样品中PAEs的预富集填料;一定比例的正己烷与乙酸乙酯混合溶液是适宜的固相萃取洗脱液。优化实验条件下,各种样品基质中PAEs的加标回收率高于58%,方法相对标准偏差(RSD)小于10.5%(n=6);方法对沉积物样品中PAEs的检出限(DL,3σ)最低,在0.3 μg/kg(邻苯二甲酸二丁酯)~5.2 μg/kg(邻苯二甲酸二异壬酯)之间;对近岸/河口海水样品的检出限(DL,3σ)在6 ng/L(邻苯二甲酸二丙酯)~67 ng/L(邻苯二甲酸二异癸酯)之间,能满足上述各类复杂基质样品中16种PAEs测定的需要。     

Engineering chemistry for the future of chemical synthesis

Synthesis is changing in response to our modern resource conscious world. The principles of green chemistry are evolving as the interfaces and boundaries in science are less obvious and providing a new stimuli for future discovery. The invention and application of new chemical reactivity continues to be a primary driver since this opens up so many strategic opportunities for synthesis. However, the manual intensive efforts behind such activity inevitably lead to the need for more machine based approaches. Indeed, the engineering of chemistry delineated in this Symposium in Print seeks to collate some of the recent progress and innovation in the area with contributions from its visionary practitioners.     

Accurate measurement of uranium isotope ratios in soil samples using thermal ionization mass spectrometry equipped with a warp energy filter

A chemical and mass-spectrometric procedure for uranium isotopic analysis using a thermal ionisation mass spectrometer equipped with a Wide Aperture Retardation Potential energy filter has been developed and applied to uranium isotopic measurements for various soil samples. Soil samples were digested using a microwave digestor. Uranium was isolated from soil samples by the chemical separation procedure based on the use of anion-exchange resin and UTEVA extraction chromatography column. The isotope ratios were measured for two certified reference materials by using a VG Sector 54-30 thermal ionisation mass spectrometer in dynamic mode with Faraday cup and Daly ion counting system. Replicates of standard reference materials showed excellent analytical agreement with established values supporting the reliability and accuracy of the method. Precision of the ²³⁵U/²³⁸U ratio was achieved by a correction factor of 0.22% amu as a function of ion-beam intensity with sample loads of around 250?ng of U. The resulting reproducibility for standards and soil samples was better than 0.2% at two standard deviations (SD). Uranium isotopic compositions have been determined in several reference soil samples such as Buffalo river sediment, NIST 2704, river sediment SRM 4350b and ocean sediment NIST-4357 and a Chernobyl soil sample. There was a significant deviation from the natural uranium in comparison with Chernobyl soil samples.     

Use of the Eurachem guide on method validation for determination of uranium in environmental samples

Three analytical methods for determination of uranium in environmental samples by a fluorescence technique have been validated and compared in accordance with the Eurachem Guide on method validation. The first method depends on uranium separation from iron using the mercury anode technique; in the other two methods uranium is separated from iron on an anion exchange column by use of either a solution of hydrochloric acid containing ascorbic acid and hydrazine hydrate or a dilute sulfuric acid solution. Detection limits, repeatability, reproducibility, and recovery coefficient were the main validation characteristics. The results showed that better statistical values can be achieved by using the third method. Control charts for in-house control samples and international intercomparison samples have also shown that the third method is more statistically stable with time. In addition, uncertainties of measurement were estimated and compared for the three methods. It was found that the Eurachem Guide and comparison of quality statistical validation data can be good tools for selection of the appropriate method for an application.     

铀在地下水中的化学形态模拟研究

用EQ3/6程序模拟研究了某场址地下水中U的化学形态,并模拟了在不同的pH、温度T、总碳?∑C?浓度、U的浓度ρ(UO22 )等条件下U的化学形态,分析了其化学形态变化规律。结果表明,在该场址地下水中,铀主要以碳酸铀酰络合物形式存在。pH、T、∑C浓度变化对铀的化学形态影响较大。     

Comparison of ICP-MS and SIMS techniques for determining uranium isotope ratios in individual particles

The determination of uranium isotope ratios in individual particles is of great importance for nuclear safeguards. In the present study, an analytical technique by inductively coupled plasma mass spectrometry (ICP-MS) with a desolvation sample introduction system was applied to isotope ratio analysis of individual uranium particles. In ICP-MS analysis of individual uranium particles with diameters ranging from 0.6 to 4.2 μm in a standard reference material (NBL CRM U050), the use of the desolvation system for sample introduction improved the precision of ²³⁴U/²³⁸U and ²³⁶U/²³⁸U isotope ratios. The performance of ICP-MS with desolvation was compared with that of a conventionally used method, i.e., secondary ion mass spectrometry (SIMS). The analysis of test swipe samples taken at nuclear facilities implied that the performance of ICP-MS with desolvation was superior to that of SIMS in a viewpoint of accuracy, because the problems of agglomeration of uranium particles and molecular ion interferences by other elements could be avoided. These results indicated that ICP-MS with desolvation has an enough ability to become an effective tool for nuclear safeguards.     

Adaptable coordination of U(IV) in the 2D-(4,4) uranium oxalate network: From 8 to 10 coordinations in the uranium (IV) oxalate hydrates

Crystals of uranium (IV) oxalate hydrates, U(C₂O₄)₂·6H₂O (1) and U(C₂O₄)₂·2H₂O (2), were obtained by hydrothermal methods using two different U(IV) precursors, U₃O₈ oxide and nitric U(IV) solution in presence of hydrazine to avoid oxidation of U(IV) into uranyl ion. Growth of crystals of solvated monohydrated uranium (IV) oxalate, U(C₂O₄)₂·H₂O·(dma) (3), dma=dimethylamine, was achieved by slow diffusion of U(IV) into a gel containing oxalate ions. The three structures are built on a bi-dimensional complex polymer of U(IV) atoms connected through bis-bidentate oxalate ions forming [U(C₂O₄)]₄ pseudo-squares. The flexibility of this supramolecular arrangement allows modifications of the coordination number of the U(IV) atom which, starting from 8 in 1 increases to 9 in 3 and, finally increases, to 10 in 2. The coordination polyhedron changes from a distorted cube, formed by eight oxygen atoms of four oxalate ions, in 1, to a mono-capped square anti-prism in 3 and, finally, to a di-capped square anti-prism in 2, resulting from rotation of the oxalate ions and addition of one and two water oxygen atoms in the coordination of U(IV). In 1, the space between the _∞²[U(C₂O₄)₂] planar layers is occupied by non-coordinated water molecules; in 2, the space between the staggered _∞²[U(C₂O₄)₂·2H₂O] layers is empty, finally in 3, the solvate molecules occupy the interlayer space between corrugated _∞²[U(C₂O₄)₂·H₂O] sheets. The thermal decomposition of U(C₂O₄)₂·6H₂O under air and argon atmospheres gives U₃O₈ and UO₂, respectively.     

EVEBAT: a fast strategy for the examination of the empty space in polymer matrices

A very efficient strategy to evaluate the "free volume" and the "unoccupied volume" in polymer matrices is proposed. The method, which has been denoted EVEBAT (Empty Volume Evaluation Based on Atom-Types), emerges from the concept of atom type, which is the basis of a force field. Accordingly, the numerical treatment is minimized by analyzing the atom types used to describe the polymer matrix, which are always a few, rather than all the explicit, atoms involved in it. The performance of the new method has been pointed out by a detailed comparison with the classical insertion algorithms.     

Synthesis of novel chitosan resin derivatized with serine moiety for the column collection/concentration of uranium and the determination of uranium by ICP-MS

A chitosan resin derivatized with serine moiety (serine-type chitosan) was newly developed by using the cross-linked chitosan as a base material. The adsorption behavior of trace amounts of metal ions on the serine-type chitosan resin was systematically examined by packing it in a mini-column, passing a metal solution through it and measuring metal ions in the effluent by ICP-MS. The resin could adsorb a number of metal cations at pH from neutral to alkaline region, and several oxoanionic metals at acidic pH region by an anion exchange mechanism. Uranium and Cu could be adsorbed selectively at pH from acidic to alkaline region by a chelating mechanism; U could be adsorbed quantitatively even at pH 3–4. Uranium adsorbed on the resin was easily eluted with 1 M nitric acid: the preconcentration (5-, 10-, 50- and 100-fold) of U was possible. The column treatment method was used prior to the ICP-MS measurement of U in natural river, sea and tap waters; R.S.D. were 2.63, 1.13 and 1.37%, respectively. Uranium in tap water could be determined by 10-fold preconcentration: analytical result was 1.46±0.02 ppt. The resin also was applied to the recovery of U in sea water: the recovery tests for artificial and natural sea water were 97.1 and 93.0%, respectively.     

Development of method for determination and preconcentration of uranium in water samples using XAD-4 resin loaded with Br-PADAP

In the present work, a minicolumn of XAD-4 loaded with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) is proposed as a preconcentration system for uranium determination in well, tap and mineral water samples by spectrophotometer using arsenazo III as the chromogenic reagent. Initially, a two-level (2³) full factorial design was used for the preliminary evaluation of three factors, involving the following variables: sampling flow rate, elution flow rate, and pH. This design has revealed that, for the studied levels, buffer concentration and pH were significant factors. When the experimental conditions established in the optimization step were pH = 8.6, and an elution flow rate of 8.6 mL min^?1 using 0.5% m/v ascorbic acid, this system has allowed for the determination of uranium with a detection limit (LOD) (3σ/S) of 0.05 μg L^?1 and a quantification limit (LOQ) (10σ/S) of 0.16 μg L^?1. The precision expressed as the relative standard deviation (R.S.D.) of 0.8% and 1.9% at 10.0 and 1.0 μg L^?1, respectively- and a preconcentration factor of 184.5 for a sample volume of 50.0 mL. Accuracy was confirmed by uranium determination in the standard reference material, NIST SRM 1566b trace element units in Oyster Tissue samples, and spike tests with recuperations ranging from 93.2 to 105%; the procedure were applied for uranium determination in tap water, well water, and drinking water samples collected from Caetité and Cruz das Almas Cities, Bahia, Brazil. Five water samples were analyzed the uranium concentrations varied from 0.50 to 2.07 μg L^?1     

Extractive scintillating polymer sensors for trace-level detection of uranium in contaminated ground water

This contribution describes the synthesis of robust extractive scintillating resin and its use in a flow-cell detector for the direct detection of uranium in environmental waters. The base poly[(4-methyl styrene)-co-(4-vinylbenzyl chloride)-co-(divinylbenzene)-co-(2-(1-napthyl)-4-vinyl-5-phenyloxazole)] resin contains covalently bound fluorophores. Uranium-binding functionality was added to the resin by an Arbuzov reaction followed by hydrolysis via strong acid or trimethylsilyl bromide (TMSBr)-mediated methanolysis. The resin was characterized by Fourier-transform infrared spectroscopy and spectrofluorometry. Fluorophore degradation was observed in the resin hydrolyzed by strong acid, while the resin hydrolyzed by TMSBr-mediated methanolysis maintained luminosity and showed hydrogen bonding-induced Stokes' shift of ∼100 nm. The flow cell detection efficiency for uranium of the TMSBr-mediated methanolysis resin was evaluated at pH 4, 5 and 6 in DI water containing 500 Bq L⁻¹ uranium-233 and demonstrated flow cell detection efficiencies of 23%, 16% and 7%. Experiments with pH 4, synthetic groundwater with 50 Bq L⁻¹ uranium-233 exhibited a flow cell detection efficiency of 17%. The groundwater measurements show that the resins can concentrate the uranyl cation from waters with high concentrations of competitor ions at near-neutral pH. Findings from this research will lay the groundwork for development of materials for real-time environmental sensing of alpha- and beta-emitting radionuclides.     

Reversed-phase liquid chromatography using mandelic acid as an eluent for the determination of uranium in presence of large amounts of thorium

Studies were carried out for the separation of uranium (U) and thorium (Th) on reversed-phase (RP) C₁₈ columns using mandelic acid as an eluent. Retention of thorium–mandelate on the unmodified stationary phase was found to be greater than that of uranyl–mandelate under the pH conditions employed. Th retention capacity of the stationary phase was determined as a function of pH and MeOH content of the mobile phase. The optimised parameters allowing U elution prior to Th were utilized for the determination of small amounts of U in the presence of large amounts of Th. The method has been used for the determination of U in synthetic samples with Th/U amount ratios up to 100,000 (10 μg/g of U) without any pre-separation, employing a particulate C₁₈ column. Effect of concentration of ion interaction reagents (IIRs) on the retention was studied to understand the mechanism of adsorption of their mandelate complexes onto the stationary phase. The experiments conducted unequivocally prove that thorium–mandelate complex is neutral whereas uranyl–mandelate complex is anionic in nature.     

An improved extraction chromatographic resin for the separation of uranium from acidic nitrate media

The preparation and characterization of a new extraction chromatographic resin exhibiting extraordinarily strong retention of hexavalent uranyl ion over a wide range of nitric acid concentrations and very high selectivity for U(VI) over Fe(III) and numerous other cations is described. This new material (designated U/TEVA-2) comprises a novel liquid stationary phase consisting of an equimolar mixture of diamyl amylphosphonate (DA[AP]) and Cyanex 923^® (a commercially available trialkyl-phosphine oxide, TRPO) sorbed on silanized silica or Amberchrom CG-71. Cyanex 923 is shown to be preferable to a related TRPO, Cyanex 925^®, due to its lower viscosity and higher selectivity for U(VI) over Fe(III). The retention of uranyl nitrate by the U/TEVA-2 resin, as measured by the k′ values (number of free column values to peak maximum) is >5000 from approximately 0.1 to 8 M HNO₃. The ability of the new resin to strongly and selectively retain U(VI) from such a wide range of acid concentrations, along with its favorable physical properties, make it a good candidate for application in the separation and preconcentration of U(VI) from complex environmental, biological, and nuclear waste samples for subsequent determination.     

Fast and accurate expression for the Voigt function. Application to the determination of uranium M linewidths

The Voigt function is the convolution between a Gaussian and a Lorentzian distribution. The numerical implementation of this function is required in diverse areas of physics and applied mathematics. An explicit representation for the Voigt function is developed in terms of series of trigonometric and hyperbolic functions. The obtained expression permits a very fast evaluation of Voigt profiles with a degree of accuracy higher than the one required for spectroscopy applications. In addition, this expression is implemented in a numerical algorithm of parameter optimization in electron probe microanalysis, and applied to determine natural linewidths for several transitions to the uranium M levels.     

氧化铟基纳米催化剂用于二氧化碳选择性加氢的研究进展

二氧化碳选择性加氢反应不仅能减少二氧化碳排放, 而且能够制备多种含碳产物, 可以作为生产高附加价值化学品与燃料的平台化合物. 然而, 由于二氧化碳的高化学惰性、 碳-碳偶联过程的高能垒和诸多的竞争反应, 开发高效的纳米催化剂以促进二氧化碳的活化并转化为多样性的产物显得至关重要. 最近, 基于氧化铟的纳米催化剂在催化二氧化碳加氢方面受到广泛关注, 主要由于其成本低廉, 且具有丰富的氧缺陷位点, 可有效吸附并活化二氧化碳和氢气. 为深入了解反应机理并设计更高性能的潜在纳米催化剂, 需对氧化铟基纳米催化剂在二氧化碳加氢方面的研究进展进行总结. 本综述首先总结了不同晶型的氧化铟及其与金属氧化物或金属纳米粒子形成的复合催化剂用于催化二氧化碳选择性加氢制备C1产物的性能. 随后, 探讨了氧化铟与不同类型的沸石的复合物用于催化二氧化碳加氢制备C₂₊产物的性能. 最后, 提出了目前氧化铟基纳米催化剂在催化二氧化碳选择性加氢方面存在的挑战和未来的发展方向. 希望本文能够为设计具有高活性、 高选择性和高稳定性催化二氧化碳加氢的新型氧化铟基纳米催化剂提供一些思路.     

Presentation of differential laser-induced fluorimetry as a reference measurement procedure for determination of total uranium content in ores and similar matrices

The metrological principle of ‘differential technique in laser-induced fluorimetry’ analysis is discussed and recommended as a reference measurement procedure for determination of total uranium content in ores and similar matrices. The estimated relative expanded uncertainty values obtained for uranium content in standard IAEA samples are, S 1, 0.04 g/kg, S 2, 0.06 g/kg, S 3, 0.04 g/kg, and for S 4, 0.10 g/kg, respectively. These low uncertainty values obtained for uranium show high metrological quality of differential technique. This reference measurement procedure guarantees the quality of an analytical result (accuracy, high precision, reliability, comparability, and traceability). Laser-induced fluorimetry will be useful for the analysis of uranium in ores, certification of reference materials, borehole core assay, and other diverse applications in nuclear fuel cycle. Differential technique in spectrophotometry/laser fluorimetry has inherent high metrological quality. In principle, laser-induced fluorimetry is an ideal technique for the very accurate determination of uranium by the use of appropriate fluorescence-enhancing reagents and methodology depending upon the concentration of uranium and sample matrices.     

A general model for the release of active agents incorporated in swellable polymeric matrices

A theoretical model, which takes proper account of the simultaneous uptake of a liquid leachant by a polymer matrix and the consequent release of a bioactive or other solute incorporated therein, is presented and the kinetics of release predicted under various conditions is investigated. This model is shown to be both more rigorous and much more widely applicable than previous attempts to approach the above problem. Furthermore, it can be easily modified or extended, in accordance with the information available about any particular system. It is, therefore, expected that the model introduced here will prove useful as a basis for the design of monolithic controlled-release devices of this type or for the evaluation of the leachability of low-level and medium-level radioactive wastes “immobilized” in polymeric matrices.     

Application of Inductively Coupled Plasma Mass Spectrometry to the determination of uranium isotope ratios in individual particles for nuclear safeguards

The capability of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of uranium isotope ratios in individual particles was determined. For this purpose, we developed an experimental procedure including single particle transfer with a manipulator, chemical dissolution and isotope ratio analysis, and applied to the analysis of individual uranium particles in certified reference materials (NBL CRM U050 and U350). As the result, the ²³⁵U/²³⁸U isotope ratio for the particle with the diameter between 0.5 and 3.9 μm was successfully determined with the deviation from the certified ratio within 1.8%. The relative standard deviation (R.S.D.) of the ²³⁵U/²³⁸U isotope ratio was within 4.2%. Although the analysis of ²³⁴U/²³⁸U and ²³⁶U/²³⁸U isotope ratios gave the results with inferior precision, the R.S.D. within 20% was possible for the measurement of the particle with the diameter more than 2.1 μm. The developed procedure was successfully applied to the analysis of a simulated environmental sample prepared from a mixture of indoor dust (NIST SRM 2583) and uranium particles (NBL CRM U050, U350 and U950a). From the results, the proposed procedure was found to be an alternative analytical tool for nuclear safeguards.     

Current trends in the use of zero-valent iron (Fe0) for degradation of pharmaceuticals present in different water matrices

Zero-valent iron (Fe⁰) has recently been proposed as a potential candidate for the degradation of pharmaceuticals, because Fe⁰ can release dissolved iron species, activate molecular oxygen, and react with oxidant species. Additionally, due to its small particle size and large surface area, this catalyst can provide better degradation results, compared to traditional processes. This work focuses on the elimination of pharmaceuticals present in different water matrices, considering the potential harm that these substances can cause in the environment. The mechanisms of pharmaceutical removal using Fe⁰ particles include reduction, adsorption, precipitation, and oxidation processes. Most studies have focused on oxidation processes in the presence of Fe⁰ and radicals derived from oxidants such as hydrogen peroxide (H₂O₂), ozone (O₃), peroxysulfate (SO₅²⁻), peroxodisulfate (S₂O₈²⁻), and oxygen (O₂). Most of the results have shown that high percentages of pharmaceuticals can be removed, degraded, and mineralized. The mechanisms of oxidation and the parameters that influence the degradation of pharmaceuticals, as well as the possible degradation pathways, are discussed here. This review provides information on trends of different processes that use Fe⁰, considering aspects such as particle size, type of matrix, the pharmaceuticals studied, and the results obtained that can improve understanding of new advances in the field of advanced oxidation processes (AOPs) for the degradation and elimination of pharmaceuticals.     

Evaluating the potential and limitations of double-spiking species-specific isotope dilution analysis for the accurate quantification of mercury species in different environmental matrices

A new double-spiking approach, based on a multiple-spiking numerical methodology, has been developed and applied for the accurate quantification of inorganic mercury (IHg) and methylmercury (MeHg) by GC–ICPMS in different environmental matrices such as water, sediments and a wide range of biological tissues. For this purpose, two enriched mercury species (²⁰¹MeHg and ¹⁹⁹IHg) were added to the samples before sample preparation in order to quantify the extents of the methylation and demethylation processes, and thereby correct the final species concentrations. A critical evaluation of the applicability of this methodology was performed for each type of matrix, highlighting its main advantages and limitations when correcting for the conversion reactions of the species throughout the whole sample preparation procedure. The double-spike isotope dilution (DSIDA) methodology was evaluated by comparing it with conventional species specific isotope dilution (IDA) when analysing both certified reference materials and environmental samples (water, biotissues and sediment). The results demonstrate that this methodology is able to provide both accurate and precise results for IHg and MeHg when their relative concentrations are not too different (ratio MeHg/IHg > 0.05), a condition that holds for most natural waters and biotissues. Significant limitations on the accurate and precise determination of the demethylation factor are however observed, especially for real sediment samples in which the relative concentrations of the species are substantially different (ratio MeHg/IHg < 0.05). A determination of the sources of uncertainty in the methylation/demethylation factors has demonstrated that the accurate and precise measurement of the isotope ratios in the species involved in the transformations is crucial when quantifying the extents of these reactions. Although the double-spike methodology is established as a reference approach that permits the correction of most analytical biases and the accurate quantification of Hg species, some limitations have been identified for the first time in this work.