Models to estimate overall analytical measurements uncertainty: assumptions, comparisons and applications

Evaluation of analytical results reliability is of core importance as crucial decisions are taken with them. From the various methodologies to evaluate the fitness of purpose of analytical methods, overall measurement uncertainty estimation is more and more applied. Overall measurement uncertainty allows to combine simultaneously the remaining systematic influences to the random sources of uncertainty and allows assessing the reliability of results generated by analytical methods. However there are various interpretations on how to estimate overall measurement uncertainty, and thus various models for estimating it. Each model together with its assumptions has great impacts on the risks to abusively declare that analytical methods are suitable for their intended purpose. This review paper aims at (i) summarizing the various models used to estimate overall measurement uncertainty, (ii) provide their pros and cons, (iii) review the main areas of application and (iv) as a conclusion provide some recommendations when evaluating overall measurement uncertainty.     

Synthesis and photoluminescence properties of 8-hydroxyquinoline derivatives and their metallic complexes

Three new 8-hydroxyquinoline derivatives, i.e. 5-[(4-styryl-benzylidene)-amino]-quinolin-8-ol (1), 5-[(4-bromo-2-fluoro-benzylidene)-amino]-quinoline-8-ol (2) and 2-[2-(9-ethyl-9H-carbazol-2yl)-vinyl]-quinolin-8-ol (3), and their metallic complexes were synthesized and identified by ultraviolet-visible (UV-Vis), ¹H nuclear magnetic resonance (¹H NMR), Fourier transform infrared spectrometer (FTIR), mass spectrometry (MS) spectra and elemental analyses. Their fluorescence properties were studied by photoluminescence, which indicated that the luminescence wavelength of 5-and 2-substitued-8-hydroxyquinoline derivatives shifted to red in comparison with that of 8-hydroxyquinoline. Meanwhile, the fluorescence lifetime of 2-[2-(9-ethyl-9H-carbazol-2yl)-vinyl]-quinolin-8-ol and its zinc complex showed long lifetime in benzene solution. __________ Translated from Chinese Journal of Organic Chemistry, 2007, 27(3): 402–408 [译自: 有机化学]     

Longitudinal and volume viscosities of fluids confined in nanochannel

Longitudinal and volume viscosities of Lennard-Jones fluid, argon–krypton binary mixture and isotopic fluid mixture confined to nanochannels of different widths are calculated by employing theoretical technique based on Green–Kubo formula. A significant enhancement is observed in longitudinal and volume viscosities when width of the nanochannel is less than 10 nm. Effect of mass ratio of two species on longitudinal and volume viscosities is also studied for equimolar isotopic fluid mixture. It is found that enhancement in viscosity is more for larger mass ratios. It is also noted that enhancement in longitudinal and shear viscosities is more than volume viscosity.     

Density of stratified ionic melts: Experiment and theory

Densities of phases co-existing in molten ionic systems with partial miscibility out of halides of alkali metals (KBr, KI, RbBr, RbI, CsCl, CsBr, CsI) with lithium fluoride are determined in a broad temperature interval by a method of hydrostatic weighing. A linear decrease in the difference between phase densities with increasing temperature is found for all systems. By studying a molten KBr-LiF mixture, this regularity is traced up to a critical miscibility point. The critical index of the order parameter, calculated from these data happens to equal 1/2 and coincide with results predicted by mid-field theory.     

Thermodynamic analysis of LiF-BeF2 and KF-BeF2 melts by a structural model

An earlier structural model for binary silicate melts and glasses is extended to MF-BeF₂ (M = Li, K) systems. The evaluation of the thermodynamic properties as well as the phase diagrams for the binary LiF-BeF₂ system and the integral enthalpy of mixing of the KF-BeF₂ system are carried out with this model. This thermodynamic model is based on the assumption that each alkali fluoride produces the depolymerization of BeF₂ network with a characteristic free energy change. A least squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analysed and represented with a small number of parameters. The model predicts the chain-length distribution of polymeric ions, even though these are not explicitly treated as structural units of the model. The calculated fluoride polyanion chain-length distribution for the LiF-BeF₂ system is in quantitative agreement with the predictions reported in the literature.     

meso-四(对烷氧苯基)卟啉及其金属配合物的合成、表征及液 晶性

合成了meso-四(对烷氧苯基)卟啉及其Cu,Co,Zn,Pb金属配合物38个,其中14个为未见文献报道的新化合物。用元素分析,IR,UV,^1HNMR,MS对其进行了表征,确证了其结构。研究了这五个系列化合物的液晶性能,发现16个化合物具有液晶性,探讨了烷氧基链长及配位金属离子对液晶性能的影响。     

高分子动力学的单链模型

高分子单链模型是高分子稀溶液理论研究的基本模型.对其进行深入地分析,不仅有助于解决高分子稀溶液体系中溶液黏度和分子链扩散等基本问题,而且能够增进人们对高分子链结构与溶液性质间关联性的理解.虽然基于经典连续性介质力学的流体动力学理论可以定性,甚至半定量地获得稀溶液的一些重要性质,但是,随着科学技术的发展,人们从分子水平上建立了许多描述高分子稀溶液性质的模型和理论,期望能够定量地描述高分子稀溶液的性质.本文以高分子稀溶液中3个典型的单链模型为例(包括:不含流体力学相互作用的Rouse模型、含二体流体力学相互作用的Zimm模型和含多体流体力学相互作用的部分穿透球模型),综述高分子稀溶液的重要性质,并详细地给出其动力学方程的推导过程及其重要的研究进展.特别是,对于Rouse模型,本文还将其预言结果拓展到了短链高分子流体体系;此外,还介绍了这一领域的关键科学问题、发展前景和研究方向.     

Prediction of shear viscosities using periodic perturbation method and OPLS force field

The periodic perturbation method is applied to predict shear viscosities of liquid 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol and 1,2,4-butanetriol under two thermodynamical conditions: T = 373 K, P = 0.1 MPa and T = 373 K, P = 250 MPa. A linear dependence of the calculated shear viscosities with respect to the applied perturbation forces is identified. Based on this finding, extrapolation of the calculated viscosities to zero perturbation force is applied to estimate the shear viscosities for the “undisturbed” fluids. The uncertainties of the estimates are calculated using the block average method. The predicted values compare favorably with the experimental data. Although the force field is optimized using equilibrium properties (liquid densities and vaporization enthalpies), calculated results demonstrate that the force field can be used to predict the kinetic properties accurately. The force field parameters are well transferable among different state points. However, transferring parameters among different molecules should be executed with caution.     

A new method to estimate the atomic volume of ternary intermetallic compounds

The atomic volume of an A_xB_yC_z ternary intermetallic compound can be calculated starting from volumes of some proper A-B, A-C and B-C binary phases. The three methods by Colinet, Muggianu and Kohler, originally used to estimate thermodynamic quantities, and a new method here proposed, were tested to derive volume data in eight systems containing 91 ternary phases with the known structure. The comparison between experimental and calculated volume values shows the best agreement both for the Kohler method and for the new proposed procedure.     

Spontaneous electrochemical transport reactions in ionic and ionic-electronic salt melts: The production of diffusion coatings

Extensive material concerning the interaction of metals in ionic and ionic-electronic salt melts is presented. The mechanism and character of the phenomenon of the directed spontaneous transport of metals by their ions in salt melts are established. Examples of application of this phenomenon for depositing diffusion coatings on metals and alloys (by aluminum, beryllium, boron, zinc, titanium, chromium, silicon, and so on, as well as by two-component coatings) are presented.     

Electrophoretic behaviour and viscosities of metal oxides in mixed surfactant systems

 The electrokinetic behavior and viscosity of anatase and alumina in mixed-surfactant solutions were investigated. Sodium dodecylsulfate and nonionic polyoxyethylene ethers were investigated as model surfactants. Pure nonionic surfactants adsorbed on anatase and coated the particles, so that the zeta potential was nearly zero near the critical micelle concentration of surfactant. At higher surfactant concentrations, an increase in the zeta potentials was observed, suggesting a change in the microstructure of the adsorbed layer. Addition of nonionic surfactant to positively charged anatase and alumina with some preadsorbed sodium dodecylsulfate reversed the surface charge of the oxide to negative, indicating enhanced coadsorption of the anionic surfactant. At higher concentrations of the nonionic surfactant, the charge reversed back to positive. Nonionic surfactants did not reverse the surface charge of these oxides in the absence of the anionic surfactant. Coenhanced adsorption of nonionic and anionic surfactants was used to stabilize alumina at the isoelectric point, where neither surfactant adsorbed appreciably on its own. These results suggest a dramatic change in conformation of the surfactant chains in mixed systems. Further explanation and justification of the proposed changes in adsorbed surfactant conformation require spectroscopic evidence. Received: 12 March 1997 Accepted: 22 July 1997     

Speed of sound,isentropic compressibilities and viscosities of ternary non-electrolyte solutions at 303.15 K

Measurements of ultrasonic speeds, isentropic compressibilities and viscosities were carried out for six ternary mixtures namely dimethylsulphoxide (1) + 1,2-dichlorobenzene (2) + 1-alkanols (3) at 303.15 K. The 1-alkanols include 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol. The ultrasonic speeds of these ternary mixtures were also evaluated on the basis of Jacobson's free length theory and Schaaff's collision factor theory. From the viscosity data, deviations in viscosity and interaction parameters for various models were also calculated. An attempt has also been made to explain the nature of intermolecular interactions in the light of deviation in isentropic compressibilities and interaction parameter.     

Analysis of entrance pressure drop techniques for extensional viscosity determination

In this work, a novel (patent pending) orifice die design for precise extensional viscosity data determination from entrance pressure drop measurements has been developed and tested both theoretically (through Finite Element Analysis) and experimentally. It has been demonstrated that the proposed novel orifice die allows much more precise extensional viscosity measurements for polymer melts in comparison with conventional orifice dies. Moreover, it has been found that, for extensional strain hardening and extensional strain thinning polymer melts, the corrected Cogswell model and Binding/Gibson model should be preferred, respectively. Otherwise, the extensional viscosity determination can be rather erroneous.     

Viscoelasticity and self-diffusion in melts of entangled asymmetric star polymers

The crossover from linear to branched polymer dynamics in highly entangled melts was investigated with a series of asymmetric three-arm stars of poly(ethylene-alt-propylene). Two arms of equal length formed a linear backbone, kept constant through the series, while branches of various length were appended as the third arm. The materials were made by carbanionic polymerization of isoprene and the judicious application of chlorosilane linking chemistry. Subsequent saturation of the polymeric double bonds with deuterium and hydrogen, followed by fractionation, led to a set of structurally matched, nearly monodisperse pairs of deuterium-labeled and fully hydrogenous samples. Dynamic moduli were measured over wide ranges of frequency and temperature. With increasing branch length, the resulting master curves evolve smoothly, but with surprising rapidity, from the relatively narrow terminal spectrum of linear polymers to the much broader spectrum of symmetric stars. The viscosity η_o increases rapidly with branch length, and the diffusion coefficient D, obtained by forward recoil spectrometry, decreases even more rapidly. The product η_oD, however, distinguishes the transition from linear to branched polymer dynamics most clearly: for a backbone with about 38 entanglements, the crossover is already approaching completion for a single mid-backbone branch with only about three entanglements. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1943–1954, 1997     

Determination of intrinsic viscosities of macromolecules and nanoparticles. Comparison of single-point and dilution procedures

The determination of the intrinsic viscosity by single-point determinations, like that based on the Solomon–Ciuta equation, have been proposed as efficient alternatives to dilution procedures. With a basis on theoretical analysis and computer simulation, we evaluate the systematic and global bias of the Solomon–Ciuta result and show how it depends on the strength of the concentration dependence of the solution viscosity (represented by the intrinsic viscosity and the Huggins constant) and the concentration of the single measured solution. We propose that an estimated Huggins constant can be employed in a corrected Solomon–Ciuta procedure, which may yield results for the intrinsic viscosity that are even more accurate than those from the Huggins extrapolation. This gives support and utility to the use of the single-point procedure when the intrinsic viscosity has to be determined for a unique concentration. We also pinpoint specific circumstances where the dilution–extrapolation procedures should be preferred.     

低聚壳聚糖负载金属卟啉配合物的制备及生物活性研究

将低聚壳聚糖(COS)分别与不同卟啉金属(MTPPS4,M=Cu,Co,Zn)配合物结合,制备了水溶性低聚壳聚糖负载金属卟啉配合物(COS-MTPPS4),并采用红外光谱和紫外-可见光谱对其结构进行了表征。采用SRB细胞染色法,研究了壳聚糖负载金属卟啉(COS-MTPPS4)对人体肝癌细胞Bel-7402的抗肿瘤细胞活性。结果表明,金属离子配位到卟啉环中,使系列化合物对Bel-7402有较强的抑制生长活性,IC50值均小于100μg/mL,在10～20μg/mL范围内。水溶性低聚壳聚糖金属卟啉配合物作为抗肿瘤药物有很好应用前景。     

Densities,viscosities and refractive indices of 1-alkyl-3-propanenitrile imidazolium chloride ionic liquids

In this study, a series of nitrile-functionalised imidazolium ionic liquids ([C₂CN Rim]Cl, where R?=?butyl, hexyl and octyl) were synthesised by reacting imidazole with acrylonitrile and then with butyl, hexyl and octyl chlorides, respectively. The structure of these compounds were established using ¹H NMR, FT-IR and elemental analyses. The densities and viscosities were measured at T?=?(293.15–353.15?K), whereas the refractive index was measured at T?=?(293.15–333.15?K) and empirical correlations were proposed to represent this study. The decomposition temperatures were determined using a thermogravimetric analyser. The thermal expansion coefficients were also calculated and reported.     

Intradiffusion coefficients of all species in aqueous gallium perchlorate solutions and solution viscosities at 25°C

Intradiffusion coefficients of all species (cation, anion and solvent) and viscosities have been measured for aqueous solutions of gallium perchlorate in the concentration range 0–2.3 mol-kg^–1 at 25°C. The perchlorate ion intradiffusion measurements were made using³⁶ClO ₄ ^– as the tracer species in diaphragm cell experiments. The development of a method to synthesize³⁶ClO ₄ ^– from³⁶Cl^– by electrolysis is described. The perchlorate intradiffusion coefficients results show a concentration dependence that is very similar to that for D(Cl^–) in corresponding trivalent metal chloride solutions. A simple hydration analysis based on all the transport results estimates a total (effective) cation hydration for gallium within a 0–2 mol-kg^–1 range of 10 (±1.5).     

Thermomechanical analysis (TMA) correlated to differential scanning calorimetry (DSC) for ageing study of some metallic glasses

To characterize the ageing of some metallic glasses, a correlated study of the differential scanning calorimetry method (DSC) and of the thermomechanical analysis (TMA) emphasizes the specificity of the latter. We analyzed metallic glasses which have been produced either by chemical methods or by melt spinning techniques. Using TMA and DSC, we have established that the relaxation of metallic glasses is strongly dependent on treatment applied: either thermal or mechanical history. Conversely, we do not observe large differences between DSC and TMA analysis for the crystallisation. From experimental data, we try to modelize the behaviour of this type of materials under operating conditions.The authors wish to thank Dr. H. Warlimont, Dr. Hilzinger and Dr. G. Herzer of Vaccumschmelze GmbH (Hanau F.R.G), Dr. E. Illekova and Dr. P. Duhaj of Institute of Physics (Bratislava, Tchecoslovaquie) for the scientific collaboration during which the melt spinned metallic glasses were supplied.