The ring-air technique: An alternative to the ring-oven technique in circular thin-layer chromatography

A technique is described in which a ring of air is used to produce sample concentration by solvent evaporation on high-performance thin-layer chromatography plates. The technique is compared to the ring-oven technique and both are evaluated by using a dye mixture. Both techniques are employed to reduce the size of relatively large spots on the plates in an attempt to match the resolution obtained from small spots in circular chromatography.     

Estimation of pore size distribution in MCM-41-type silica using a simple desorption technique

A recently developed dynamic desorption technique is used for obtaining vapor isotherms on porous materials. This gravimetric technique does not require any preliminary calibration and is based on analyzing the kinetics of liquid evaporation from a porous sample under quasi-steady state conditions. The crucial feature of the technique is concerned with the fact that no vapor pressure measurements are necessary. The technique is illustrated by desorption of benzene vapors from mesoporous silica MCM-41. To calculate the pore size distribution, the Derjaguin–Broekhoff–de Boer theory in its combination with the Wheeler model for capillary condensation is used. In the calculations, the reference data on benzene adsorption on a nonporous silica gel from two different sources (published by different authors) are applied. The mean mesopore sizes estimated from desorption isotherms are shown to be in a fair agreement with the calculations through the geometrical method based on the X-ray diffraction data. The dynamic desorption technique can serve as an additional tool for the characterization of a porous media.     

The use of the ratios of intensities of spectral lines for X-ray fluorescence analysis of metal alloys and oxide materials

An X-ray fluorescence analysis technique is proposed, which is based on using ratios of intensities of spectral lines. The technique includes performing calculations for evaluation of calibration equations, which allows using few reference samples or carrying out standardless analysis, if necessary. That parameters of the calibration equations depend linearly on concentrations of disturbing elements allows one to simplify taking their influence into account. To apply the developed technique to analysis of samples containing a significant amount of undetectable light elements, a use of a dependence of intensity ratio of the characteristic radiation of the X-ray tube’s anode, coherently and incoherently scattered by a sample, on a total content of undetectable elements is proposed. The technique’s adequacy is demonstrated by analysis of standard steel samples, metal cuttings and iron-ore materials.     

Oral malodor,assessed by closed-loop,gas chromatography,and ion-trap technology

A method is described for the analysis of volatile organic compounds in saliva and tongue coating samples. The techniue is based on an off-line preconcentration step by means of a closed-loop trapping system followed by gas chromatography-ion trap detection. With the closed-loop technique, the volatile organic compounds(VOCs) are released from the matrix and trapped on an adsorbent without interference of water. The VOCs are released from the adsorbent into the gas chromatograph by thermdesorption. After separation, identification of the compounds is performed by ion trap technology. By this technique 82 compounds could be demonstrated in saliva and tongue coating samples. The technique is also used to demonstrate the formation of volatile bacterial fermentation compounds when a protein substrate is added to tongue coating samples. It is considered a very promising tool in further research on oral malodor.     

Melting Point and Composition Distribution of Polyolefins by Fractionation

The fractionation technique described in this paper was used to characterize the melting-point, monomer, and blocking distributions for polymers and copolymers. It is different from the molecular-weight fractionation technique in that the fractions are obtained by using a single solvent to extract the solid polymer below its melting point at stepwise-increasing temperatures. The reproducibility of this technique is excellent, and the technique is sufficient to distinguish pellet-to-pellet variation in a commercially available polypropylene. It was used to show the influence of preparation variables on the melting-point distributions of polyethylene and polypropylene and on the monomer and blocking distribution of copolymers, and to distinguish copolymers from blends.     

Atomic absorption spectrometric determination of Cd,Pb, Zn,Cu, Co and Fe in oyster tissue by direct atomization from the solid state using the graphite furnace platform technique

This paper describes a simple and rapid method for direct determination of traces of Cu, Zn, Pb, Co, Fe and Cd in the NBS oyster tissue, SRM No. 1566, by graphite furnace atomic absorption spectrometry. The solid sampling technique has been used and this results in much higher relative sensitivity by avoiding large dilution factors involved in the sample dissolution technique. The solid sampling technique also greatly reduces or eliminates serious risk of introducing contamination and/or loss of analytes involved in sample dissolution. The organic matrix of the oyster tissue is burnt off and removed by using a well-defined selective volatilization technique. Loss of Cd during charring (pyrolysis) stage is prevented by forming a relatively thermally stable compound of cadmium by adding (NH₄₂SO₄ solution to the oyster tissue sample. Also, quantitative data are presented on the effectiveness of the platform technique in removing matrix interferences. The platform technique uses an anisotropic pyrolytic graphite platform which is inserted into a commercial graphite tube.     

Noncontact measurement of thermal and optical parameters of biological tissues and materials using IR laser radiometry

A technique for simultaneous measurements of the thermal diffusivity, specific heat, and effective absorbtion coefficient was developed. The technique is based on local heating of a sample by laser radiation and thermal imager measurement of the temperature field dynamics in the surface layer in both the heating and cooling stages. The technique includes a program for calculating the laser-induced temperature field in the sample volume and the determination of three parameters by the Levenberg-Marquardt algorithm to provide the best fit of calculations to experimental results. The statistical error of thermal diffusivity, specific heat, and effective absorbtion coefficient measurements was 5–6%. The technique efficiency was demonstrated by the example of the development of a thermal and optical equivalent of cartilage tissue, based on polyacrylamide hydrogel.     

电渗析法再生离子交换树脂的进展

文章介绍了电渗析法再生离子交换树脂原理和适用的工艺流程。长期以来此法因电流效率低下而阻碍了其工业应用。最近此法在流程上作了变化，并在处理含铜废液的实验设备上取得了成功，电流效率提高到30～40％。这是进一步推广应用此法的可喜进展。     

分子印迹技术在生物大分子分离识别中的应用

分子印迹技术是近些年发展起来的模拟抗体-抗原相互作用原理的新技术。该文介绍了分子印迹技术的产生和发展,重点介绍了生物大分子印迹聚合物的制备条件、聚合方法及其识别机理,并对该技术的应用前景及目前存在的问题进行了探讨。     

Digital autoradiography (DA) in quantification of trace level beta emitters on concrete

In the framework of dismantling of nuclear facilities, there is a strong need to obtain analytical results on residual radioactivity especially on concrete but also on metal surfaces. Since investigation of hundreds of m² areas by the standard Wipe test method is difficult, a semi quantitative digital autoradiography (DA) technique was developed. The DA technique is sensitive to all types of radiation and therefore it is advantageous in dismantling investigations. Recent developments on the DA technique were investigated on concrete floor of an old laboratory in which research had been carried out using ³H and ¹⁴C beta emitters. The results showed that the DA technique was a powerful tool in localization and quantification of residual radioactivity on concrete floor.     

Two-dimensional nanoparticle arrays derived from ferritin monolayers

A scalable technique for making silica coatings with embedded two-dimensional arrays of iron oxide nanoparticles is presented. The iron oxide nanoparticle arrays were formed by depositing quasi-crystalline ferritin layers, an iron storage protein with an iron oxide mineral core, on solid substrates by a spread-coating technique based on evaporation-induced convective assembly. The layer of protein molecular arrays was then encapsulated in a silica matrix film deposited from a sol precursor. The organic protein shell of the ferritin molecules was then removed by controlled pyrolysis, leaving ordered iron oxide cores bound in the silica matrix. This article is the first report on combining convective self-assembly of proteins with sol-gel techniques of oxide film formation. The technique is technologically feasible and scalable to make coatings of encapsulated ordered magnetic clusters tens of cm(2) or larger in size.     

The rotating particles probe: A new technique to measure interactions between particles and a substrate

We demonstrate a new probing technique to measure physicochemical interactions between particles and a substrate in a fluid. The technique is based on the measurement of field-induced rotation of individual magnetic particles in contact with the substrate. The parallel measurement of many particles with single-particle resolution gives reliable statistics in a short time. Using this technique, the interaction between streptavidin-coated magnetic particles and a glass substrate is measured for various buffer conditions. Increased binding is quantified for increasing ionic strength and decreasing pH. The results are found to be in agreement with calculations of electrostatic interactions. We also apply the technique to study how binding is reduced by blocking the substrate with albumin.     

Motion of redox molecules in solution monitored by the highly-sensitive EQCM technique

The behavior of redox molecules in solution that was not detected by electrochemical techniques was measured by a highly-sensitive electrochemical quartz crystal microbalance (EQCM) technique that has been improved in this study to obtain a high sensitivity of EQCM measurement in solution. The improved EQCM technique allowed to monitor the motion of a redox molecule, that is an access of the molecule to an electrode surface and repulsion from the surface during redox. An EQCM technique currently in use has measured adsorption of redox molecules on an electrode surface or polymerization on the surface caused by a chemical reaction following redox, which exhibits an enough large mass change response to detect with an EQCM measurement. However, access and repulsion of redox molecule, which is a slight motion of the molecule near on electrode surface, has not been detected and investigated by an EQCM technique, because the mass change response seems to be very small. In this study, the redox behavior of methyl viologen on a bare gold surface, pyridinethiol surface and methylpyridinethiol surface was investigated. Although the three electrodes give the same cyclic voltammogram of methyl viologen, the three are different in QCM response recorded at the same time as the voltammetry. Access/repulsion of methyl viologen within an electrical double layer was monitored by the highly-sensitive EQCM technique.     

Motion of redox molecules in solution monitored by the highly-sensitive EQCM technique

The behavior of redox molecules in solution that was not detected by electrochemical techniques was measured by a highly-sensitive electrochemical quartz crystal microbalance (EQCM) technique that has been improved in this study to obtain a high sensitivity of EQCM measurement in solution. The improved EQCM technique allowed to monitor the motion of a redox molecule, that is an access of the molecule to an electrode surface and repulsion from the surface during redox. An EQCM technique currently in use has measured adsorption of redox molecules on an electrode surface or polymerization on the surface caused by a chemical reaction following redox, which exhibits an enough large mass change response to detect with an EQCM measurement. However, access and repulsion of redox molecule, which is a slight motion of the molecule near on electrode surface, has not been detected and investigated by an EQCM technique, because the mass change response seems to be very small. In this study, the redox behavior of methyl viologen on a bare gold surface, pyridinethiol surface and methylpyridinethiol surface was investigated. Although the three electrodes give the same cyclic voltammogram of methyl viologen, the three are different in QCM response recorded at the same time as the voltammetry. Access/repulsion of methyl viologen within an electrical double layer was monitored by the highly-sensitive EQCM technique.     

Determination of one-dimensional crystal structures using the double Patterson function

The properties and previous use of the double Patterson function in x-ray crystallography are briefly reviewed followed by an account of a new iterative technique, based on the double Patterson, which is being developed by the author. The technique starts with an approximation to the double Patterson which does not require phases, then improves the approximation by making it conform to the known projections and known magnitudes of the Fourier coefficients. The latter are 3-phase structure invariants and estimating their phases is an important step in the direct determination of structure factor phases. Tests carried out on one-dimensional centro-symmetric structures show that the technique is successful. At best, it determines correct phases for all 3-phase invariants. At worst, it fails to improve on the estimate of all phases being zero. It consistently does very much better than the B_{3, 0} formula which is also based on the double Patterson. Further development is necessary to apply the technique to non-centrosymmetric structures and to real structures in three dimensions.     

Thermal desorption characterisation of molecularly imprinted polymers. Part I: a novel study using direct-probe GC-MS analysis

A novel thermal desorption technique using a direct-probe device (Chromatoprobe) attached to a gas chromatograph–mass spectrometer is presented for the thermal pretreatment, characterisation and analysis of molecularly imprinted polymers. The technique is demonstrated as effective for the removal of volatile materials, including template and unreacted monomers, from methacrylic acid–ethylene glycol dimethacrylate copolymers imprinted with 2-aminopyridine. Mass spectrometry is a powerful technique for polymer bleed characterisation. Thermal desorption studies on reloaded template and related compounds are reported as a means of assessing polymer morphology, specific binding by imprinted polymers compared with reference non-imprinted polymers and selective binding by an imprinted polymer for its template. Calibration studies on the thermal desorption technique using an internal standard are presented with R ² > 0.999. The technique provides a novel method for assessment of polymer thermal stability, composition and morphology.     

Size selective assembly of colloidal particles on a template by directed self-assembly technique

We report a simple and effective approach to organize micron- and submicron-sized particles in a size selective manner. This approach utilizes the template assisted directed self-assembly technique. A topographically patterned photoresist surface is fabricated and used to create an ordered array of colloidal particles from their aqueous suspensions. Assembly of particles on this template is then achieved by using a conventional spin coating technique. Feasibility of this technique to form a large area of patterned particle assemblies has been investigated. To arrange the particles on the template, the physical confinement offered by the surface topography must overcome a joint effect of centrifugal force and the hydrophobic nature of the photoresist surface. This concept has been extended to the size selective sorting of colloidal particles. The capability of this technique for sorting and organizing colloidal particles of a particular diameter from a mixture of microspheres is demonstrated.     

EMULSIONS CHARACTERIZED BY MEANS OF TIME DOMAIN DIELECTRIC MEASUREMENTS (TDS). TECHNICAL APPLICATIONS

The authors have in previous contributions determined dielectric properties of W/O-emulsions by applying the Time Domain Dielectric Spectroscopy technique. The main findings are summarized here. The influence of droplet shape and flocculation on the dielectric parameters characteristic of the emulsions is discussed. A technique developed for a dielectric investigation of electrically induced coalescence is demonstrated, together with experimental results from surveys on emulsions stabilized both by commercial and natural surfactants.     

Sub-nm resolution depth profiling of the chemical state and magnetic structure of thin films by a depth-resolved X-ray absorption spectroscopy technique

Development and recent progress of a depth-resolved X-ray absorption spectroscopy (XAS) technique are presented, together with future prospects. The technique has been developed by controlling the probing depth of the electron-yield XAS data, which depends on the electron emission angle. This novel technique enables us to achieve depth profiling of the magnetic structure of thin films with a sub-nm depth resolution by using X-ray magnetic circular dichroism (XMCD) in X-ray absorption, which provides quantitative information on the element-specific spin and orbital magnetic moments. The chemical state and electronic structure at the surface and interface are also investigated by depth-resolved XAS analysis. As for future prospects, a three-dimensional micro XAS technique is being developed by combining an X-ray microbeam with depth-resolved XAS. Moreover, it is expected to manipulate magnetic anisotropy by using element-specific and depth-resolved magnetic anisotropy energies obtained from the depth-resolved XMCD to design thin films and multilayers with proper elements and proper thicknesses. The observation of the spin dynamics at the interface will be also possible in future by adopting the pump-probe method.     

Crosslinked polyacrylamide-hydrazide (paah) as matrix for the gel entrapment of cells and enzymes - an overview

The development and use of a gel entrapment technique designed for the immobilization of viable, sensitive cells is described. The method is based on the controlled chemical cross-linking of prepolymerized, linear polyacrylamide partially substituted with acylhydrazide groups, by glyoxal. The methodology, applications and advantages of this technique for the immobilization of cells and enzymes by gel entrapment are reviewed.