Palladium(II) acetates: Synthesis and molecular transformation scheme

Known methods for synthesis of a trinuclear molecular form of palladium(II) acetate, [Pd₃(CH₃COO)₆], are analyzed and a number of new techniques that enable reliable control over the type of the product obtained and provide its high yield are suggested. A molecular transformation scheme is suggested. This scheme takes into account the formation of both forms of palladium acetate and also the formation of the structurally similar [Pd₃(CH₃COO)₃NO₂].     

TGA/FT-IR: Thermogravimetric analysis with fourier transform infrared detection of evolved gases

Thermogravimetric analysis (TGA) is a widely employed technique for measuring the change in weight of a sample as a function of temperature or time in a controlled atmosphere. FT-IR has been utilized with success in the identification of gases [1]. The combination of these two techniques permits a complete characterization of materials in terms of thermal stability and decomposition mechanisms [2]. A complete integrated system for TGA/FT-IR analysis is described.     

电感耦合等离子体质谱(ICP-MS)法测定地球化学样品中金时样品前处理条件的优化

依据地球化学样品分析方法第4部分:金量的测定泡塑富集-电感耦合等离子体质谱法。在大量实践的基础上总结了样品前处理过程中样品的焙烧、溶样、振荡吸附、解脱时间的合理控制,以及样品分析前处理过程中的一些操作注意事项。最终确定样品焙烧时间1h,溶样时间40min,震荡吸附时间30min,硫脲水浴解脱时间30min。经过对大批量实验样品及国家一级金标准物质测定验证后得出:适当优化条件可以满足绝大多数样品的分析准确度、精密度等质控分析要求,并且可以提高分析效率。尤其对于大批量分析任务,如区域化学地质普查。可以在相同的实验设备、人员配备的基础上,提高分析效率,降低能耗。     

An electrochemical cell for simultaneous electrochemical and spectroelectrochemical measurements under semi-infinite diffusion conditions and thin-layer conditions

A combination cell to accomplish simultaneous electrochemical and spectroelectrochemical measurements under both thin-layer and semi-infinite diffusion conditions is described and characterized. Fibre optics and a reflective electrode are used to couple the cell to the spectrophotometer. This allows different electrode materials to be used. Moreover, the cell is thermostatically controlled and equipped with a magnetic stirrer, and can be used for temperatures down to −40°C.The application of electrochemical pulse and sweep techniques are demonstrated. Dynamic spectroelectrochemical techniques such as linear sweep and cyclic voltabsorptometry (LSVA and CVA) as well as the corresponding derivative voltabsorptometric techniques derivative linear voltabsorptometry (DLSVA) and derivative cyclic voltabsorptometry (DCVA) are also applicable under thin-layer conditions. DLSVA and DCVA are the optical analogues of linear sweep and cyclic voltammetry. No epoxy cement or other sealing compounds are required and the solution comes in contact with only quartz, Teflon and the electrodes. Under aprotic conditions the cell response is in accordance with theory down to a solution thickness of 15 μm, where rapid exhaustive electrolysis intrinsic to thin-layer electrochemistry can be achieved in less than 1 s.The electrochemical and spectroelectrochemical characterization of the cell demonstrated that this design is very well suited to different electrochemical pulse and sweep techniques with simultaneous spectroscopic characterization of reaction products under finite and semi-infinite diffusion conditions in organic solvents. This offers the opportunity for cross-correlations of the electrochemical and spectroscopic information, which should lead to more reliable results. The adjustment of different thin-layer thicknesses is highly reproducible and the exchange of the solution inside the thin-layer cavity with the bulk solution after each thin-layer experiment can be easily performed. The electrochemical behaviour of the cell is in accordance with theory for cyclovoltammetric measurements under both bulk and thin-layer conditions. Derivative voltabsorptometric techniques are applicable and the response of the cell is in accordance with theory, particularly under finite diffusion conditions. The use of a bifurcated optical fibre bundle allows a more flexible experimental arrangement, and the application of a triple split bundle for the investigation of light-sensitive electron-transfer compounds [34,35] is in progress. The third end of the optical fibre bundle will be used to apply additional selective irradiation to convert electron-transfer-active photochromic compounds inside the thin-layer cavity depending on the redox state.An additional aspect of the current investigations is the application of the present cell for electrogenerated chemiluminescence (ECL) [36,37]. The highly reflecting electrode and the integrated stirrer are advantageous for this type of measurement. Finally, further work is in progress to utilize the integrated temperature control of the cell for spectroelectrochemistry at low temperatures, particularly with more unusual solvents like liquid sulphur dioxide [38] and liquid dimethylamine [39].     

Quality assurance of X-ray spectrometry for chemical analysis

Three different techniques, energy dispersive X-ray fluorescence, total reflection X-ray fluorescence and particle induced X-ray emission were used to initiate an evaluation program on quality assurance (QA) procedures applied to X-ray spectrometry for chemical analysis. The use of standard methodologies to assure the statistical control of measurement data is the main objective of this work. Certified Reference Materials were used and up to 15 certified elements were analyzed to carry out the QA procedures. For the internal quality control, z-scores were calculated and control charts were produced. The plotted elemental data illustrate statistically controlled methodologies for the majority of the determinations. Even the cases where the control charts exhibit values out of control limits, the z-scores are below 3 in absolute value, indicating satisfactory results. Concerning external quality control the statistical methods applied showed that the results obtained for the three techniques are comparable, although some significant differences occur, mainly due to sample preparation. Therefore, the techniques are traceable to certified reference materials and the data gathered so far, enable to initiate a database for QA procedures.     

1,3,5-triazine-based mass spectral tagging of one-bead one-compound libraries

A triazine-based mass encoding strategy that accommodates cleavable linker, isotopic labeling, and diversity receptor moieties is reported. The resulting triazine-based tags, which are coupled to bifunctionalized TentaGel resin in a one-pot transformation, enable the construction of a 1-oxa-2,8-diazaspiro[4.5]dec-2-ene-7-carboxamide library and facilitate decoding by equalizing the ionization potential of the liberated tags in single bead MALDI-TOF experiments as well as balancing the reactivity of the starting tags in the resin coupling step. [reaction: see text].     

Gas concentration programming – a new approach to sample controlled thermal analysis

Sample controlled thermal analysis (SCTA) is the generic name used to describe a family of techniques where the heating rate is not pre-determined as in conventional thermal analysis, but altered as some function of a property of the sample (i.e. mass loss, rate of gas evolution, etc.). We demonstrate here a new form of SCTA, where the reaction rate for gas–solid reactions can be controlled by programming the concentration of the reactive gas whilst keeping the temperature constant.     

Overview of sample introduction techniques prior to GC for the analysis of volatiles in solid materials

Sample preparation and introduction techniques are very critical steps in gas chromatography analysis and particularly in the analysis of volatiles in solid samples. In these cases, they can be divided into two main categories: direct and indirect approaches, based on how the solid sample is treated, i.e. with and without dissolution (or extraction) of analytes from the solid sample. To enable routine application, coupling with sample preparation techniques (especially solid or solvent‐based microextractions) is needed to achieve automation. Here, an overview of the most common sample introduction techniques for gas chromatography with their advantages and drawbacks is presented and discussed, including references to relevant examples. So, this review can serve as guidance for new users.     

Chemistry-structure-simulation or chemistry-simulation-structure sequences? The case of MIL-34, a new porous aluminophosphate

A new aluminophosphate, MIL-34, is investigated from its as-synthesized structure to its calcined microporous form. Single-crystal X-ray diffraction measurements on the as-synthesized MIL-34 (Al(4)(PO(4))(4)OH x C(4)H(10)N, space group P-1, a = 8.701(3) A, b = 9.210(3) A, c = 12.385(3) A, alpha = 111.11(2) degrees, beta = 101.42(2) degrees, gamma = 102.08(2) degrees, V = 863.8(4) A(3), Z = 2, R = 3.8%) reveal a 3-D open framework where Al atoms are in both tetrahedral and trigonal bipyramidal coordinations. It contains a 2-D pore system defined by eight rings where channels along [100] cross channels running along [010] and [110]. CBuA molecules are trapped at their intersection. (27)Al, (31)P, and (1)H MAS NMR spectroscopies corroborate these structural features. Calcination treatments of a powder sample of the as-synthesized MIL-34 indicate its transformation into the related template-free structure that is stable up to 1000 degrees C. Lattice energy minimizations are then used in order to anticipate the crystal structure of the calcined MIL-34, starting with the knowledge of the as-synthesized structure exclusively. Energy minimizations predict a new regular zeotype structure (AlPO(4), space group P-1, a = 8.706 A, b = 8.749 A, c = 12.768 A, alpha = 111.17 degrees, beta = 97.70 degrees, gamma = 105.14 degrees, V = 846.75 A(3), Z = 2) together with a thermodynamic stability similar to that of existing zeotype AlPOs. Excellent agreement is observed between the diffraction pattern calculated from the predicted calcined MIL-34 and the experimental X-ray powder diffraction pattern of the calcined sample. Finally, the atomic coordinates and cell parameters of the calcined MIL-34 predicted from the simulations are used to perform the Rietveld refinement of the calcined sample powder pattern, further corroborated by (27)Al and (31)P NMR measurements. This unique combination of experiment and simulation approaches is an interesting and innovative strategy in materials sciences, where simulations articulate the prediction of a possible template-free framework from its as-synthesized templated form. This is especially valuable when straightforward characterizations of the solid of interest with conventional techniques are not easy to carry out.     

High-throughput screening and optimization approaches for chiral compounds by means of microfluidic devices

Chiral separations facilitated using microchip devices are reviewed in this paper. The first research paper on this topic was published in 1999. It was seen that analysis times are greatly reduced compared with more conventional techniques such as liquid chromatography and capillary electrophoresis, and that these devices enable the separation of chiral molecules. Method optimization can be conducted in a rather easy manner, reducing the total method development time. Finally, minute amounts of sample and buffer are used during analysis, which makes the systems ultra-economical. Although the number of applications in the chiral separation field on these miniaturized systems is still rather limited, they exhibit much potential towards high-throughput screening. Some efforts are, however, still needed regarding detection modes, because derivatisation of the samples is often needed to enable their detection.     

Combined diagnostics of the structure of complex oxide materials and metal catalysts by synchrotron X-ray diffraction

The combined use of different synchrotron radiation (SR) X-ray diffraction techniques is shown to be effective in collecting the most complete structural information about an object being studied. The high intensity of SR and its spectral-angular distribution enable researchers to conduct experiments with high angular resolution, experiments using resonance effects, time-resolved experiments, and experiments where the sample is exposed to the effects of temperature and reaction medium. Results are presented of two studies where the distinctive features of SR play the key role.     

Multiple‐injection high‐throughput gas chromatography analysis

Multiple‐injection techniques have been shown to be a simple way to perform high‐throughput analysis where the entire experiment resides in a single chromatogram, simplifying the data analysis and interpretation. In this study, multiple‐injection techniques are applied to gas chromatography with flame ionization detection and mass detection to significantly increase sample throughput. The unique issues of implementing a traditional “Fast” injection mode of multiple‐injection techniques with gas chromatography and mass spectrometry are discussed. Stacked injections are also discussed as means to increase the throughput of longer methods where mass detection is unable to distinguish between analytes of the same mass and longer retentions are required to resolve components of interest. Multiple‐injection techniques are shown to increase instrument throughput by up to 70% and to simplify data analysis, allowing hits in multiple parallel experiments to be identified easily.     

Quantitative portable gamma-spectroscopy sample analysis for non-standard sample geometries

Utilizing a portable spectroscopy system, a quantitative method for analysis of samples containing a mixture of fission and activation products in nonstandard geometries was developed. This method was not developed to replace other methods such as Monte Carlo or Discrete Ordinates but rather to offer an alternative rapid solution. The method can be used with various sample and shielding configurations where analysis on a laboratory based gamma-spectroscopy system is impractical. The portalle gamma-spectroscopy method involves calibration of the detector and modeling of the sample and shielding to identify and quantify the radionuclides present in the sample. The method utilizes the intrinsic efficiency of the detector and the unattenuated gamma fluence rate at the detector surface per unit activity from the sample to calculate the nuclide activity and Minimum Detectable Activity (MDA). For a complex geometry, a computer code written for shielding applications (MICROSHIELD) is utilized to determine the unattenuated gamma fluence rate per unit activity at the detector surface. Lastly, the method is only applicable to nuclides which emit gamma-rays and cannot be used for pure beta or alpha emitters. In addition, if sample self absorption and shielding is significant, the attenuation will result in high MDA's for nuclides which solely emit low energy gamma-rays. The following presents the analysis technique and presents verification results using actual experimental data, rather than comparisons to other approximations such as Monte Carlo techniques, to demonstrate the accuracy of the method given a known geometry and source term.     

Electrokinetic sample transport in a microchannel with spatial electrical conductivity gradients

Studies of the sample transport in a microchannel with the electrical conductivity gradient are critical to develop techniques for on-chip sample transport control. A numerical model presented in this paper, consisting of the electrical potential equation, full Navier-Stokes equation and species conservation equation, is used to simulate sample transport in a microchannel with the consideration of the conductivity gradient. There are two situations studied here, sample pumping (where sample separation is minimized by employing a high-conductivity buffer in the sample region), and sample stacking (where sample separation is expedited by using a low-conductivity buffer as the sample carrier). The effects of applied electrical potential, sample diffusion coefficient and the ratio of conductivity of the driving buffer over the sample carrying buffer are investigated by using the developed model.     

The Role of Column Switching in Analysing Complex Samplest

Abstract

Our objective in using column switching is primarily to achieve the desired separation in the minimum analysis time. Complimentary to this aim is the need for sample and column cleanup followed by column re-equilibration. Finally, all operations should be capable of automation. Fundamental to column switching methodology is the concept of Zone cutting, where part of the chromatogram is transferred to another column. This forms the basis of sample cleanup and is a very versatile and powerful method. Multiple zone cutting is also possible to further increase the scope of cleanup or to minimise analysis time. Zone cutting is also complimentary to the techniques of trace enrichment and recycling. Examples will be given involving the use of these techniques in the analysis of complex matrices such as urine, plant extracts, wine and serum. The latter will be used to propose a novel approach to the quantitative analysis of anti-convulsants in serum using hexobarbital as internal standard.     

The role of column switching in analysing complex samples

Our objective in using column switching is primarily to achieve the desired separation in the minimum analysis time. Complimentary to this aim is the need for sample and column cleanup followed by column re-equilibration. Finally, all operations should be capable of automation. Fundamental to column switching methodology is the concept of Zone cutting, where part of the chromatogram is transferred to another column. This forms the basis of sample cleanup and is a very versatile and powerful methods. Multiple zone cutting is also possible to further increase to scope of cleanup or to minimise analysis time. Zone cutting is also complimentary to the techniques of trace enrichment and recycling. Examples will be given involving the use of these techniques in the analysis of complex matrices such as urine, plant extracts, wine and serum. The latter will be used to propose a novel approach to the quantitative analysis of anti-convulsants in serum using hexobarbital as internal standard.     

Enantiomer separation of drugs by micellar electrokinetic chromatography using chiral surfactants

A review surveying enantiomer separations by micellar electrokinetic chromatography (MEKC) using chiral surfactants is described. MEKC is one of the most popular techniques in capillary electrophoresis, where neutral compounds can be analyzed as well as charged ones, and the use of chiral micelles enable one to achieve the enantioseparation. The chiral MEKC systems are briefly reviewed according to the types of chiral surfactants along with typical applications. As chiral micelles or pseudostationary phases in MEKC, various natural and synthetic chiral surfactants are used, including several low-molecular-mass surfactants and polymerized surfactants or high-molecular-mass surfactants. Cyclodextrin modified MEKC using chiral micelles is also considered.     

Capillary isoelectric focusing hyphenated to single- and multistage matrix-assisted laser desorption/ionization-mass spectrometry using automated sheath-flow-assisted sample deposition

In this paper CIEF combined with MALDI-MS is described using a sheath-liquid-assisted automatic sample deposition from the separation capillary onto a MALDI target. Sample/matrix preparation techniques on the target resembling the dried droplet and the thin layer methods were evaluated in the context of the automatic spotting. Volatile buffers were used as IEF catholyte solutions. Test samples consisting of tryptic peptides, glycopeptides, and phosphopeptides of well-known proteins showed that CIEF-MALDI-MS can be used as effective preseparation method prior to MS, allowing to obtain the amino acid sequence coverage of proteins similar to that achieved with CZE-MALDI-MS and CZE-ESI-MS. Particularly, completeness and reliability of glycopeptide analysis is much enhanced by the preseparation. The effect is less pronounced but still significantly found with phosphopeptides present in the test protein. Finally, a test sample of five standard proteins demonstrates the suitability of this technique also for the treatment of intact proteins. This technique has potential to emerge as a faster method analogous and complementary to 2-DE and to IPG-IEF-MALDI-MS demonstrated before by the group of Loo [1].     

The determination of organochlorine compounds and petroleum hydrocarbons in a seaweed sample: results of a world-wide intercomparison exercise

A seaweed sample (Fucus sp.) was prepared, homogenised and distributed to laboratories worldwide as the IAEA-140 intercomparison material for the analysis of organochlorine compounds and petroleum hydrocarbons. A total of 80 laboratories from 51 countries reported results for this sample. The data sets reported by laboratories were evaluated statistically and the mean concentration values could be computed with 95% confidence limits for a large number of analytes. The accuracy of the analytical performance of each laboratory has been introduced by using Z-scores. The spread of results reported generally indicates that the accurate determination of many persistent organic pollutants, such as hexachlorobenzene, lindane, Aroclors or fluoranthene, is still difficult for many laboratories. The final results of this intercomparison exercise enable individual participants to assess their performance and, where necessary, to introduce appropriate modifications in their analytical procedures. Furthermore, as a series of statistical criteria was fulfilled for a number of compounds, the sample IAEA-140 can now be used as a reference material for quality control in the determination of chlorinated compounds and petroleum hydrocarbons in environmental samples.     

In situ liquid SIMS analysis of uranium oxide

Trace analysis of nuclear materials in solid particles collected in the environment or particles in liquid slurry generated in nuclear material manufacturing processes can pinpoint elemental, organic, and isotopic signatures of nuclear fuel cycle activities and processes. Such information can support nuclear safeguards programs by increasing our ability to detect undeclared nuclear materials, routine activities for safeguarding at declared facilities, and illicit activities. However, trace radioactive material analysis in liquids and slurries is challenging using bulk approaches. For example, one drawback of sensitive analysis such as inductively coupled plasma mass spectrometry (ICP-MS) is that sample is consumed or destroyed as a result of the technical approach. We developed a vacuum compatible microfluidic interface to enable surface analysis of liquids and solid–liquid interactions using time-of-flight secondary ion mass spectrometry (ToF-SIMS). In this work, we illustrate the initial results from the analysis of liquid uranium oxide standard solutions using in situ liquid SIMS. Because the liquid SIMS analysis is almost nondestructive, the same sample can then be analyzed by other analytical techniques or saved for future reference. Consequently, multimodal analysis is possible. Our results demonstrate that in situ liquid SIMS can be used as a new approach to analyze radioactive materials in liquid and slurry forms of relevance to diverse applications.