A critical review of methods of isolating and separating the noble metals--II. Ion-exchange and solvent extraction

This review deals with ion-exchange and solvent extraction methods of separating the seven noble metals, published subsequent to the previous reviews and prior to January 1966. The noble metal species present in solution are discussed in so far as they relate to separation and determination.     

A critical review of methods of isolating and separating the noble metals-III Chromatography, precipitation and fire assay

This review deals with the chromatographic, precipitation and fire-assay methods of separating the seven noble metals, published subsequent to the previous reviews and prior to January 1966. The noble metal species present in solution are discussed in so far as they relate to separation and determination.     

Analytical separation and detection methods for flavonoids

Flavonoids receive considerable attention in the literature, specifically because of their biological and physiological importance. This review focuses on separation and detection methods for flavonoids and their application to plants, food, drinks and biological fluids. The topics that will be discussed are sample treatment, column liquid chromatography (LC), but also methods such as gas chromatography (GC), capillary electrophoresis (CE) and thin-layer chromatography (TLC), various detection methods and structural characterization. Because of the increasing interest in structure elucidation of flavonoids, special attention will be devoted to the use of tandem-mass spectrometric (MS/MS) techniques for the characterization of several important sub-classes, and to the potential of combined diode-array UV (DAD UV), tandem-MS and nuclear magnetic resonance (NMR) detection for unambiguous identification. Emphasis will be on recent developments and trends.     

Analytical methods for nano-bio interface interactions

Knowledge on the interactions between engineered nanomaterials (ENMs) and biological systems is critical both for the assessment of biological effects of ENMs and for the rational design of ENM-based products. However, probing the events that occur at the nano-bio interface remains extremely challenging due to their complex and dynamic nature. So far, the understanding of mechanisms underlying nano-bio interactions has been mainly limited by the lack of proper analytical techniques with sufficient sensitivity, selectivity and resolution for characterization of nano-bio interface events. Moreover, many classic bioanalytical methods are not suitable for direct measurement of nano-bio interface interactions. These have made establishing analytical methodologies for systematic and comprehensive study of nano-bio interface one of the most focused areas in nanobiology. In this review we have discussed some representative developments regarding analytical techniques for nano-bio interface characterization, including the improvements of traditional methods and the emergence of powerful new technologies. These developments have allowed ultrasensitive, real-time analysis of interactions between ENMs and biomolecules, transformations of ENMs in biological environment, and impacts of ENMs on living systems on molecular or cellular level.     

Analytical methods for tracing plant hormones

Plant hormones play important roles in regulating numerous aspects of plant growth, development, and response to stress. In the past decade, more analytical methods for the accurate identification and quantitative determination of trace plant hormones have been developed to better our understanding of the molecular mechanisms of plant hormones. As sample preparation is often the bottleneck in analysis of plant hormones in biological samples, this review firstly discusses sample preparation techniques after a brief introduction to the classes, roles, and methods used in the analysis of plant hormones. The analytical methods, especially chromatographic techniques and immuno-based methods, are reviewed in detail, and their corresponding advantages, limitations, applications, and prospects are also discussed. This review mainly covers reports published from 2000 to the present on methods for the analysis of plant hormones.     

Analytical methods for water supply systems

Summary An analytical system for monitoring and controlling water treatment plants is presented. The single measuring devices (flow, temperature, turbidity, pH, pCl, conductivity, COD, pressure difference, alkalinity, hardness, free chlorine) are described.

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Analytische Methoden für Wasserversorgungseinrichtungen

Zusammenfassung Ein analytisches System zur Überwachung und Steuerung von Wasseraufbereitungsanlagen wird vorgestellt. Die einzelnen Meßstellen (Fließgeschwindigkeit, Temperatur, Trübung, pH, pCl, Leitfähigkeit, CSB, Druckdifferenz, Alkalität, Härte, freies Cl₂) werden beschrieben.

Presented at the 6th Annual Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria.     

Analytical potential of hybrid nanoparticles

The growing use of nanoparticles in the analytical process in recent years has set a new trend towards the simplification of analytical methods and improvement of their performance. Miniaturization and nanotechnology have allowed new analytical challenges to be met. Hybrid nanoparticles in particular possess exceptional properties enabling further improvement of analytical methods. Despite the continuous developments in their synthesis and characterization, hybrid nanomaterials have scarcely been used in analytical chemistry, however. This paper discusses the analytical potential of hybrid nanoparticles in terms of their special characteristics and properties, and describes their analytical applications.     

Analytical methods for the determination of tungsten

Methods developed and employed in the recent literature (1969-1975) for the detection and determination of tungsten in a wide variety of matrices are reviewed. This paper is a supplement to the books, monographs and review papers which deal with the earlier literature.     

Electrophoretic methods for separation of nanoparticles

This article reviews progress in the application of electrophoretic techniques for the separation of nanoparticles. Numerous types of nanoparticles have recently been synthesised and integrated into different products and procedures. Consequently, analytical methods for the efficient characterisation of nanoparticles are now required. Several studies have revealed that gel electrophoresis can readily be used for separating nanoparticles according to their size or shape. However, many other studies focused on separation of nanoparticles by CE. In some cases nanoparticles could be separated by CZE, simply using pure buffer as the BGE. In other studies, buffer additives (most often SDS) were used, enabling fast separations of metallic nanoparticles by size. Other CE methods also allowed for separation of nanoparticle conjugates with biomolecules. Dielectrophoresis is yet another electrophoretic technique useful in separation and characterisation of nanoparticles; particularly nanotubes. Detection methods often used after electrophoretic separation include UV/Vis absorption and fluorescence spectroscopy. Examples of recent and relevant older reports are presented here. The authors conclude that electrophoretic methods for nanoanalysis can provide inexpensive and efficient tools for quality assurance and safety control; and as a consequence, they can augment transfer of nanotechnologies from research to industry.     

Analytical methods for pesticide residues in rice

Rice consumption has increased worldwide over recent decades, as it has become one of the most common foods. Although the analysis of environmental samples coming from rice areas has been well documented, there is less information regarding the analysis of pesticide residues in rice-grain samples.Rice (paddy, brown and white) can be considered a complex matrix, leading to difficulties in the application of the different multiresidue methods described in the literature. This review addresses and compares the principal extraction and clean-up methodologies [e.g., liquid-liquid extraction, solid-phase extraction, pressurized-liquid extraction, QuEChERS (quick, easy, cheap, effective, rugged and safe), gel-permeation chromatography and supercritical-fluid extraction - with QuEChERS-based methods being the most frequently employed].Traditionally, the determination of pesticide residues in rice has been based on gas chromatography with mass spectrometry (MS). But the application of new classes of pesticides has driven laboratories to increase the use of liquid chromatography with tandem MS. The limits of detection and quantification are in the ranges 0.09-90 μg/kg and 1-297 μg/kg, respectively, for the methodologies reported. These values agree with the current internationally-accepted maximum residue limits (MRLs).Based on the European Union (EU) database, more than 3000 analyses of pesticide residues in rice have been performed by official EU laboratories over the past decade. Of these, 6% reported pesticide residues above the MRLs.Physico-chemical properties can explain the occurrence of pesticides in rice commodities: lipophilic pesticides are frequently found in brown rice, whereas fungicides are mainly found in milled rice. Carbendazim, malathion, iprodione, tebuconazole, quinclorac and tricyclazole are the pesticides most frequently found in white rice, while buprofezin, hexaconazole, chlorpyrifos and edifenphos are most commonly found in paddy rice.Pesticide-residue concentrations can be affected during rice processing - with concentrations generally lower in the final products. However, few studies focusing on primary processing have addressed the setting of precise values applicable for the processing factors.     

Analytical strategies for characterizing the surface chemistry of nanoparticles

Chemical modifications of nanoparticle (NP) surfaces are likely to regulate their activities, remove their toxic effects, and enable them to perform desired functions. It is urgent to develop analytical strategies for acquiring structural and quantitative information about small molecules linked to the surface of NP. Recent progress in characterizing the surface chemistry of NPs using nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, liquid chromatography–mass spectroscopy (LC–MS), X-ray photoelectron spectroscopy (XPS), and combustion elemental analysis are reviewed.     

Analytical and preparative methods for β-exotoxin fromBacillus Thuringensis

Summary Theβ-exotoxin fromBacillus thuringensis is a well known insecticide. The bioassay usually employed for its analysis is time-consuming and subject to many disturbances. The previously reported HPLC analysis has been shown to give erroneous results in some cases. A new analysis system has how been designed. The system is based on separation ofβ-exotoxin from the culture broth, and from various preparations containingβ-exotoxin by ion-pairing. For sample preparation in more complex matrices an method employing solid phase extraction was developed. In order to obtain a standard for quantitative analysis a preparative method for the isolation ofβ-exotoxin from concentrated culture broth after successive precipitations was also developed.     

PEO coated magnetic nanoparticles for biomedical application

This paper reports on the preparation, characterization and stealthiness of superparamagnetic nanoparticles (magnetite Fe₃O₄) with a 5 nm diameter and stabilized in water (pH ? 6.5) by a shell of water-soluble poly(ethylene oxide) (PEO) chains. Two types of diblock copolymers, i.e., poly(acrylic acid)-b-poly(ethylene oxide), PAA-PEO, and poly(acrylic acid)-b-poly(acrylate methoxy poly(ethyleneoxide)), PAA-PAMPEO, were prepared as stabilizers with different compositions and molecular weights. At pH ? 6.5, the negatively ionized PAA block interacts strongly with the positively-charged nanoparticles, thus playing the role of an anchoring block. Aggregates of coated nanoparticles were actually observed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The hydrodynamic diameter was in the 50-100 nm range and the aggregation number (number of nanoparticles per aggregate) was lying between several tens and hundred. Moreover, the stealthiness of these aggregates was assessed “in vitro” by the hemolytic CH50 test. No response of the complement system was observed, such that biomedical applications can be envisioned for these magnetic nanoparticles. Preliminary experiments of magnetic heating (10 kA/m; 108 kHz) were performed and specific absorption rate varied from 2 to 13 W/g_(Fe).     

Microchip integrating magnetic nanoparticles for allergy diagnosis

We report on the development of a simple and easy to use microchip dedicated to allergy diagnosis. This microchip combines both the advantages of homogeneous immunoassays i.e. species diffusion and heterogeneous immunoassays i.e. easy separation and preconcentration steps. In vitro allergy diagnosis is based on specific Immunoglobulin E (IgE) quantitation, in that way we have developed and integrated magnetic core-shell nanoparticles (MCSNPs) as an IgE capture nanoplatform in a microdevice taking benefit from both their magnetic and colloidal properties. Integrating such immunosupport allows to perform the target analyte (IgE) capture in the colloidal phase thus increasing the analyte capture kinetics since both immunological partners are diffusing during the immune reaction. This colloidal approach improves 1000 times the analyte capture kinetics compared to conventional methods. Moreover, based on the MCSNPs' magnetic properties and on the magnetic chamber we have previously developed the MCSNPs and therefore the target can be confined and preconcentrated within the microdevice prior to the detection step. The MCSNPs preconcentration factor achieved was about 35,000 and allows to reach high sensitivity thus avoiding catalytic amplification during the detection step. The developed microchip offers many advantages: the analytical procedure was fully integrated on-chip, analyses were performed in short assay time (20 min), the sample and reagents consumption was reduced to few microlitres (5 μL) while a low limit of detection can be achieved (about 1 ng mL(-1)).     

Synthesis of magnetic nanoparticles for analytical applications

A simple method based on magnetically assisted chemical separation has been developed for analytical purposes. In this method, morin-modified magnetic nanoparticles were used for the selective extraction and preconcentration of copper ions from aqueous solutions. The influence of different parameters, such as the presence of the morin extractant, the amount of morin extractant loaded on the nanoparticles, the pH, adsorption time and the type and minimum amount of eluent required for elution of the copper from the magnetic nanoparticles, were evaluated. The detection limit of the proposed method followed by ICP–OES was found to be 1.3 µg L^?1 and a dynamic linear range of 10–200 µg L^?1 was obtained. The relative standard deviation was less than 5%. The method was applied to the recovery and determination of copper in real samples.     

Silica matrices for embedding of magnetic nanoparticles

This paper presents a study regarding the formation of hybrid gels starting from tetraethyl orthosilicate (TEOS), polyvinyl alcohol (PVA) and 1,3-propanediol (PD) and their thermal evolution to mesoporous silica matrices. The possibility of obtaining homogenously dispersed cobalt ferrite inside the silica matrix starting from (TEOS–PVA–PD–Metal Nitrates) gels was also studied. The formation of the hybrid gels TEOS/PVA/PD with different compositions was studied by FT-IR spectrometry and thermal analysis, in order to evidence the interaction between the diol with the organic and the inorganic polymers. Both thermal analysis and FT-IR spectrometry have evidenced the formation of physical and chemical interaction between polyols and the siloxane network. Elemental mapping performed by SEM-EDX technique evidenced the formation of homogenous hybrids both in the presence of the absence of 1,3-propanediol. SEM images of the powders obtained by annealing the hybrid xerogels at 600 °C have evidenced the formation of mesoporous silica. By thermal treatment of the (TEOS–PVA–PD–Metal Nitrates) gels, 30%CoFe₂O₄/70%SiO₂ (mass percent) nanocomposites uniformly dispersed in silica matrix with characteristic magnetic properties, have been successfully synthesized.     

Analytical equilibrium gradient methods

Analytical equilibrium gradient methods are non-linear separation methods in which the separation mechanism involves a force gradient along the separation channel. These methods can be classified into two categories: those in which the gradient is a field gradient applied along the separation channel (i.e., field gradient), and those in which the channel is subjected to a constant field with a gradient formed in some other property (i.e., constant field). Standard deviation of peak width, resolution and peak capacity are important parameters in characterizing equilibrium gradient methods, and general expressions can be obtained from considering both the point of force acting on the analyte and the basic flux equation. Several successful examples, such as density gradient sedimentation, isoelectric focusing and electromobility focusing are discussed. Based on equilibrium gradient methods in the field gradient category, a method to dynamically improve peak capacity is described. An example of such an approach is given using electromobility focusing.     

Biofunctional magnetic nanoparticles for protein separation and pathogen detection

Recent successful syntheses of monodispersed magnetic nanoparticles have offered a unique opportunity to control and probe biological interactions using magnetic force. This paper highlights a general strategy to generate biofunctional magnetic nanoparticles, illustrates applications for these nanoparticles in protein separation and pathogen detection, and analyzes the high sensitivity and high selectivity achieved by this system.