Mercury analysis: a special example of species analysis

Summary Mercury species analysis requires the determination of numerous different compounds with very different behaviour regarding environment and toxicity. For these differing species several new and more sensitive analytical methods have been developed and tested. Mercury species cannot be detected directly in most cases, and are normally derivatized by different agents and determined by different detector systems. In a new HPLC method with photometric detection more than 10 different organomercurials could be analysed as their thio-ethanol complexes. By alkylation of mercury compounds they can be separated by GC and analysed with an AAS or AFS as detector. Volatile organic species of Hg can be separated on Carbotrap^®, where Hg⁰ is not adsorbed, and analysed thereafter. With atomic fluorescence the detection limit for Hg⁰ measurement is improved significantly when compared with the widely used atomic absorption method. Results obtained with this new method are shown and discussed. Future developments for species analysis are outlined; not only to analyse the covalent metal — carbon/oxygen compounds — primary species-analysis — but also compounds with ionic or complex bonding: secondary species-analysis. With these developments, prediction of species behaviour in the environment, including toxicity assessment and decontamination proposals, should be made possible.     

Transient analysis of a vibrating reed: Error analysis

The error analysis for the transient vibrating reed test is developed based on a linearized approximation. Tables are given for the efficient utilization of the equations in evaluating the accuracy range of test data.     

Frontal analysis on a microchip

Conventional microchip applications involving capillary electrophoresis (CE) typically inject a sample along one channel and use an intersection of two channels to define the sample plug--the portion of sample to be analysed along a second channel. In contrast to this method of zone separation, frontal analysis proceeds by injecting sample continuously into a single channel or column. Frontal analysis is more common in macroscopic procedures but there are benefits in sensitivity and device density to its application to electrophoresis on microchips. This work compares conventional microchip zone analysis with frontal analysis in the separation of PCR products. Although we detect on the order of 5000 fluorophores with a compact instrument using the zone separation CE method, we found a several-fold increase in the effective signal-to-noise ratio by using a frontal analysis method. By removing the need for additional channels and reservoirs the frontal method would allow device densities to be significantly increased, potentially improving the cost-effectiveness of microchip analyses in applications such as medical diagnostics.     

Stepwise injection analysis as a new method of flow analysis

Various versions of flow analysis techniques (continuous-flow, flow-injection, and sequential-injection analysis) and their relative advantages and disadvantages are considered. Cyclic (stepwise) injection analysis is proposed, and the general principles of this technique are described.     

Transient analysis of a viscoelastic torsion pendulum: Error analysis

The error analysis for the transient torsion pendulum test is developed based on a linearized approximation. Tables are given for the efficient utilization of the equations in evaluating the accuracy range of the test data.     

Thermal analysis of a model bio-membrane

Thermal properties of some shedded snake skins in comparison with human skins are represented by thermogravimetry (TG), derivative thermogravimetry (DTG), and differential thermal analysis (DTA) to predict process condition as dermal pathway for administration of drugs or it be used as model membranes for permeation studies. Thermal behavior by TG/DTG and DTA curves for four kinds of shedded snake skins as Boelens Python (BP), Eastern Indigo Snake (EIS), Emerald Tree Boa (ETB), and Cascavel (CBR) were similar in relation to their decomposition temperatures at 100 °C and 230–400 °C of its constituents, however, their properties were different in the residue content (inorganic or carbonaceous substances). Similar thermal properties were also exhibited by human skins’ samples, however, they presented different residue and constituents’ content.     

Microdrop analysis of a bead-based immunoassay

The progress to electrochemical detection of a microbead-based immunoassay in small volumes has led to a reduced assay time and lower detection limits. Three electrochemical techniques are described for an immunoassay with detection in a microdrop. The techniques are amperometric detection with a rotating disk electrode (RDE), a microelectrode, and an interdigitated array (IDA) electrode. An enzyme-labeled sandwich immunoassay with mouse IgG as the model analyte is used to demonstrate the three techniques. The microbead assay is carried out in a test tube using a magnet to control bead collection. Once the immunocomplex is formed on the microbead, the beads are transferred to a microdrop where the enzyme, either alkaline phosphatase or β-galactosidase, generates 4-aminophenol (PAP). PAP is oxidized at the electrode with an applied potential of +290 mV vs. Ag/AgCl. For all three techniques, the upper limit of the dynamic range was 1000 ng/ml mouse IgG, and the detection limits were: 50 ng/ml for the RDE, 40 ng/ml for the microelectrode, and 26 ng/ml for the IDA electrode.     

Sedimentation analysis using a magnetic fluid

An improved sedimentation method for analyzing particle size distribution is described. The method is primarily distinguished by the application of a magnetic fluid as a medium in which particles move. This circumstance makes it possible to measure particle velocities and sizes with magnetic sensors. The theory of the method and experimental data are discussed.     

Fractal analysis of a discotic texture

The dendritic-type texture displayed by low molar mass discotic charge transfer systems possessing a columnar hexagonal ordered phase has been subjected to a fractal analysis. The diffusion limited aggregation approach was used to simulate the growth of the texture. The results are that the texture displays a fractal geometry and that the prominent features of the discotic texture are correctly reflected by the simulated clusters, including the fractal dimension. The conclusion is that the texture is conditioned by the lattice structure of the discotic phase and the kinetic processes, the sticking rules in the terms of diffusion limited aggregation model, responsible for the growth of the texture.     

Thermal analysis from a numerical aspect

This publication surveys the present state of thermal analysis from a numerical aspect. It deals with the applied methods and techniques, the substances studied, and the journals publishing papers on thermal analysis.

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Zusammenfassung In der Veröffentlichung wird ein Überblick über die gegenwärtige Situation der thermischen Analyse gegeben. Auf Grund von aus Thermal Analysis Abstracts entnommenen Daten werden die Anwendungsmethodik, die verschiedenen Techniken, die Untersuchungsmaterialien sowie die thermoanalytische Publikationen enthaltenden Zeitschriften zusammengefaßt.

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Scaling analysis of coating of a plate or a fiber

The problem of coating a plate or a fiber through their withdrawal from a large reservoir was treated in the literature in various limiting cases. In the present paper, interpolation expressions are derived by scaling for Newtonian, Bingham, and viscoelastic fluids. The scaling analysis was also employed to explain the sharp increase in film thickness produced by inertia and the occurrence of a maximum thickness for an optimum velocity. It is also shown that, for a viscoelastic fluid, the film thickness tends to a finite value at very large withdrawal rates. An explanation is also provided for the existence of a maximum film thickness for an optimum surfactant concentration.     

Exploring a solvated dimer of Gefitinib: a quantitative analysis

Gefitinib or Iressa is an orally administered anilinoquinazoline used in cancer chemotherapy for the treatment of lung and breast cancer. It is reported to exist in two polymorphic forms, a stable form I and a metastable form II. Both of the forms belong to the triclinic P space group. In this work, we report the crystallization of Gefitinib to form a methanol solvate [systematic name: N‐(3‐chloro‐4‐fluorophenyl)‐7‐methoxy‐6‐[3‐(morpholin‐4‐yl)propoxy]quinazolin‐4‐amine methanol hemisolvate, C₂₂H₂₄ClFN₄O₃·0.5CH₃OH] that was theoretically and experimentally investigated. The unit cell is composed of two independent Gefitinib molecules (A and B) that form a stable molecular complex with methanol in the crystal lattice. To understand the crystal lattice stabilization, a combination of techniques, namely X‐ray diffraction, IR spectroscopy, thermogravimetric/differential scanning calorimetry (TG‐DSC), Hirshfeld surface analysis and CLP‐PIXEL methods were used. The analysis of the crystal structure of this dimer revealed a three‐dimensional isostructurality with the already reported form II. The A and B molecules are connected via trifurcated C—H…O and N—H…O hydrogen bonding. In addition, the presence of the methanol molecule stabilizes the crystal structure via C—H…O, N—H…O and C—H…Cl interactions between the two monomers. The IR analysis of the dimer has shown characteristic fingerprint values when compared to the commercial form. The TG‐DSC analysis of the solvated dimer is in good agreement with the patent reporting cocrystals of Gefitinib. Finally, theoretical calculations by the CLP‐PIXEL method and Hirshfeld surface and two‐dimensional (2D) fingerprint plot analysis were carried out in order to quantify the different intermolecular interactions and their energies in the crystal packing.     

NMR analysis of a pair of isomers

In this work,the structures of a pair of isomers were identified.And we showed the ability of the selective 1D version,performed the most common NMR experiments including the ID-HMBC and GOESY experiments,to determine the isomeric composition that were found in the production process of roflumilast.The experimental results proved that this method would be even more time saving and could get more reliable results.     

Thermal analysis of a white calcium bentonite

A white calcium bentonite (CaB) taken from Çaml?dere (Ankara, Turkey) region was heated at various temperatures between 100 and 1100 °C for 2 h. The mineralogy of the CaB was determined as calcium smectite (CaS), metahalloysite (MH), opal-A (OA), opal-CT (OCT), quartz (Q), feldspar (F), and calcite (C) using the X-ray diffraction patterns of the natural CaB and its heated samples. Besides the XRD patterns, the thermogravimetry, differential thermal analysis, and low-temperature nitrogen adsorption (N₂-AD) data show that the CaS lose adsorbed and hydration water up to 300 °C, dehydroxylation takes place between 300 and 750 °C, and then the 2:1 layer structure completely collapses above 900 °C. The activation energies for the dehydration and dehydroxylation were calculated as 7636 and 48838 J mol^?1, respectively, from the TG data using Coats and Redfern method. The specific surface area (S) and specific micro–mesopore volume (V) obtained from N₂-AD data were 44 m² g^?1 and 0.100 cm³ g^?1 for the natural CaB. S and V reach their maxima of 105 m² g^?1 and 0.155 cm³ g^?1, respectively, at 300 °C, remain approximately constant as the temperature increases up to 700 °C and then decrease almost in parallel with each other, reaching their minima at 900 °C. This indicates that the S and V values increase gradually during dehydration and dehydroxylation of the CaS.     

Conformational analysis of a model synthetic prodiginine

A conformational analysis of a synthetic model prodiginine was carried out. In solution this compound showed a strong preference for the β conformation, in which all the heterocycles are mutually cis. This conformation provided an ideal alignment of the three N-H groups for interacting with anions when the molecule is protonated. A different conformation was also detected in d(6)-DMSO for the mesylate salt, assigned to the α conformation, in which the C ring is engaged in an intramolecular hydrogen bond with the OMe group. The formation of a homodimer was observed in concentrated CDCl(3) solutions of the neutral free base form of this prodiginine derivative. DFT calculations and the solid state structures of the hydrochloric and methanesulfonic acid salts were in good agreement with the results observed in solution. A complete study of the relative energies of different tautomers, isomers, and supramolecular complexes supported the preference for the β conformation both in water and in the gas phase.     

Miniaturized detectors for a chemical analysis system

Recently, several studies about miniaturized chemical analysis systems fabricated with micromachining methods were reported. These systems have some advantages, such as fast response, small amount of sample, and low consumption of reagents, as compared with the conventional system. With such a small system, design of the detector units is very important to monitor analytical performance. This paper introduces some examples of micromachined detectors for miniaturized chemical analysis systems.     

Single-cell metabolite analysis on a microfluidic chip

Metabolites can directly reflect and modulate cell responses and phenotypical changes by influencing energy balances, intercellular signals, and many other cellular functions throughout the lifespan of cells.Taking into account the heterogeneity of cells, single-cell metabolite analysis offers an insight into the functional process within one cell. Microfluidics as a powerful tool has attracted significant interest in the single-cell metabolite analysis field. The microfluidic platform is possib...