The definition of primary method of measurement (PMM) of the ’highest metrological quality’: a challenge in understanding and communication

Problems with understanding, explaining and communication of the present definition of primary method of measurement are described and amendments put forward for discussion. The conclusion is drawn that in many cases more attention should be given to the measurement result and its uncertainty statement, rather than to a method. Some cases are discussed where methods might have a fundamental characteristic that other methods do not have, a condition for the epitheton ’primary’. Received: 23 December 2000 Accepted: 13 November 2000     

Capillary electrophoresis – a useful tool in speciation investigations

1. CE is shown as a tool for a more-dimensional identification of organic metal binding partners. Methods are given for a further improvement of the identification security of the organic ligands [1], when analyzing molecules of nearly equal mobility. CE is used here as a powerful tool for quality assurance and quality control in speciation investigations.2. Methods are presented for a direct separation and identification of different species. As an example, seleno organo compounds are separated from their sulphur analogues in model solutions and native samples. Standard addition methods [1, 2] as well as UV spectra of both species help to identify these molecules as seleno- or sulphur-organo compounds. Further methodological developments and separations are shown for Pt-compounds.     

Achieving traceability in chemical measurement—a metrological approach to proficiency testing

ISO/IEC 17025 requires that testing laboratories establish the traceability of their measurements, preferably to the SI units of measurement. The responsibility for establishing traceability lies with each individual laboratory and must be achieved by following a metrological approach.The results of measurements made in such a way are traceable to the standards used in method validation and to the calibration standards used during the measurement process. If these standards are traceable to SI then the measurements will also be traceable to SI.Participation in appropriate proficiency studies (an ISO/IEC 17025 requirement) enables laboratories to demonstrate the comparability of their measurements. If the materials used for the studies have traceable assigned values, then proficiency testing also provides information about measurement accuracy and confirms, or otherwise, that appropriate traceability has been established. This paper will report on a new approach for the establishment of traceable assigned values for chemical testing proficiency studies. The work is conducted at a "fit for purpose" level of measurement uncertainty, with costs contained at a level similar to previous "consensus" based proficiency studies. By establishing traceable assigned values in a cost effective way, NARL aims to demonstrate the added value of the metrological approach to participant laboratories.     

Nanocomposites: Industrial opportunity or challenge?

Polymer nanocomposites based on organically modified layered silicates are an area of substantial scientific interest and of emerging industrial practice. Despite the proven benefits of nanocomposites such as mechanical properties, barrier properties and contribution to fire retardancy, polymer nanocomposites are used today only in niche applications. The reasons for the limited growth of nanocomposites are explained through the availability of alternative solutions, processing and dispersion challenges and inferior oxidative and photooxidative stability. Recent developments show the improved dispersion of unmodified nanoclays in polyolefins with the help of selected copolymer structures. The (photo)oxidative instability of nanocomposites is compensated with adjusted stabilizer systems.     

Polymerization with Fischer-Tropsch olefins – a new challenge in polymer science

Co- and ter-polymerization of ethylene with Fischer-Tropsch derived olefins having odd carbon number and branched olefins are investigated. A method of preparation of a robust, high productivity Ziegler-Natta catalyst suitable for ethylene co-polymerization with Fischer Tropsch olefin is reviewed. In supporting titanium tetrachloride, an attempt was made to control the titanium oxidation state. The resulting experimental data were fitted to a sub-sites model that associates titanium oxidation state with catalyst activity.     

Isotope-dilution ICP–MS for trace element determination and speciation: from a reference method to a routine method?

This critical review discusses the conditions under which inductively coupled plasma–isotope dilution mass spectrometry (ICP–IDMS) is suitable as a routine method for trace element and element-speciation analysis. It can, in general, be concluded that ICP–IDMS has high potential for routine analysis of trace elements if the accuracy of results is of predominant analytical importance. Hyphenated techniques with ICP–IDMS suffer both from lack of commercially available isotope-labeled spike compounds for species-specific isotope dilution and from the more complicated system set-up required for species-unspecific ICP–IDMS analysis. Coupling of gas or liquid chromatography with species-specific ICP–IDMS, however, enables validation of analytical methods involving species transformations which cannot easily be performed by other methods. The potential and limitations of ICP–IDMS are demonstrated by recently published results and by some unpublished investigations by our group. It has been shown that possible loss of silicon as volatile SiF₄ during decomposition of a sample by use of hydrofluoric acid has no effect on trace silicon determination if the isotope-dilution step occurs during digestion in a closed system. For powder samples, laser ablation ICP–IDMS can be applied with an accuracy comparable with that only available from matrix-matched standardization, whereas the accuracy of electrothermal vaporization ICP–IDMS was strongly dependent on the element determined. The significance of easy synthesis of isotope-labeled spike compounds for species-specific ICP–IDMS is demonstrated for monomethylmercury and Cr(VI). Isotope-exchange reactions between different element species can prevent the successful application of ICP–IDMS, as is shown for iodinated hydrocarbons. It is also shown for monomethylmercury that species transformations during sample-pretreatment steps can be followed by species-specific ICP–IDMS without loss of accuracy. A relatively simple and time-efficient procedure for determination of monomethylmercury in environmental and biological samples is discussed. The method, which entails a rapid microwave-assisted isotope dilution step and in-situ extraction of the derivatized species, has good potential for routine application in the future.     

Analytical methodologies for aluminium speciation in environmental and biological samples – a review

It is recognized that aluminium (Al) is a potential environmental hazard. Acidic deposition has been linked to increased Al concentrations in natural waters. Elevated levels of Al might have serious consequences for biological communities. Of particular interest is the speciation of Al in aquatic environments, because Al toxicity depends on its forms and concentrations. In this paper, advances in analytical methodologies for Al speciation in environmental and biological samples during the past five years are reviewed. Concerns about the specific problems of Al speciation and highlights of some important methods are elucidated in sections devoted to hybrid techniques (HPLC or FPLC coupled with ET–AAS, ICP– AES, or ICP–MS), flow-injection analysis (FIA), nuclear magnetic resonance (²⁷Al NMR), electrochemical analysis, and computer simulation. More than 130 references are cited.     

Chemometrics in analytical chemistry—part II: modeling,validation, and applications

Analytical and Bioanalytical Chemistry - The contribution of chemometrics to important stages throughout the entire analytical process such as experimental design, sampling, and explorative data...     

Nanoparticle-based pseudostationary phases in CEC: a breakthrough in protein analysis?

This review focuses on major trends in nanoparticle-based pseudostationary phase (PSP) CEC since the publication of our previous reviews within nanoparticle-based CEC [Nilsson, C., et al., Electrophoresis 2006, 27, 76-83; Nilsson, C., et al., J. Chromatogr. A 2007, 1168, 212-224.]. Special attention is given to the development toward protein analysis, which is driven by the strong emergence of protein drug development in the pharmaceutical industry. Furthermore, we discuss the development in coupling different detection techniques with nanoparticle-based PSP CEC, which were originally predicted to be particularly cumbersome. However, at present, direct UV, LIF and ESI-MS have been used without any severe complications. Different types of nanoparticles used as PSP during the period include gold nanoparticles, carbon nanostructures and lipid-based nanoparticles. New materials (for example, different types of carbon nanostructures and self assembled lipid-based nanostructures) are a strong driving force for development in separation science. Finally, future trends in nanoparticles-based CEC are envisioned.     

Bulk photochromism in a tungstate-phosphate glass: a new optical memory material?

In this work, we present a new photochromic tungstate based glass which have both absorption coefficient and refractive index modified under laser exposure. The photosensitive effect is superficial under ultraviolet (UV) irradiation but occurs in the entire volume of the glass under visible irradiation. The effect can be obtained in any specific point inside the volume using an infrared femtosecond laser. In addition, the photosensitive phenomenon can be erased by specific heat treatment. This glass can be useful to substitute actual data storage supports and is a promising material for 3-dimensional (3D) and holographic optical storage.     

Meeting future needs for metrological traceability—a physicist’s view

Abstract Metrological traceability of measurement results provides the comparability needed for reliable measurement in almost every aspect of our daily life, ranging from fundamental science, through health and safety to global trade. From the authors (a physicist) perspective and understanding of recent literature, measurements in chemistry compare the amount of analyte, are often made indirectly, are sometimes not fully traceable to the SI, and metrological traceability is perhaps not always the major concern of the practising analytical chemist. The present article examines which of these views are typically chemical, and which are common to both the physicist and the chemist. Much can be gained by formulating a common understanding of basic concepts of traceability of measurement results in meeting ever-increasing demands for comparability of measurement results in both traditional as well as new areas of technology and societal concern.Based on a lecture given by the author at a mini-symposium Emerging issues in metrology in chemistry organised by the IUPAC Analytical Chemistry Division and IUPAC Working Party for Harmonisation of Quality Assurance at IAEA Headquarters, Vienna, 17th February 2004.     

The complex story of a simple Brønsted acid: unusual speciation of HBr in an ionic liquid medium

Crystalline solids, co-existing in equilibrium with the 3-methyl-1H-imidazolium bromohydrogenates(I) ionic liquid, have been characterised by X-ray diffraction analysis. The Br?nsted acidic, homo-conjugate [H(2)Br(3)](-) anions presented are discussed in terms of their structure and reactivity, in efforts to advance the understanding of Br?nsted acidity in ionic liquid media.     

Solubility challenge: can you predict solubilities of 32 molecules using a database of 100 reliable measurements?

Solubility is a key physicochemical property of molecules. Serious deficiencies exist in the consistency and reliability of solubility data in the literature. The accurate prediction of solubility would be very useful. However, systematic errors and lack of metadata associated with measurements greatly reduce the confidence in current models. To address this, we are accurately measuring intrinsic solubility values, and here we report results for a diverse set of 100 druglike molecules at 25 degrees C and an ionic strength of 0.15 M using the CheqSol approach. This is a highly reproducible potentiometric technique that ensures the thermodynamic equilibrium is reached rapidly. Results with a coefficient of variation higher than 4% were rejected. In addition, the Potentiometric Cycling for Polymorph Creation method, [PC] (2), was used to obtain multiple polymorph forms from aqueous solution. We now challenge researchers to predict the intrinsic solubility of 32 other druglike molecules that have been measured but are yet to be published.     

Dynamic reaction cell ICP-MS for determination of total As, Cr, Se and V in complex matrices: still a challenge? A review

Mass interferences, caused by atomic or polyatomic species and having the same mass/charge ratio of the analyte, can be a severe limit for a reliable assay of trace and ultratrace elements by ICP-MS. The DRC? technology uses a reaction gas to overcome these interferences. Reactions of charge exchange, atom transfer, adduct formation, condensation and analyte association/condensation are the main mechanisms. Interfering ions tend to react with the gas exothermally, while, the analyte reacts endothermally. Selecting the most appropriate reaction gas in DRC-ICP-MS is the very critical point for the determination of strongly interfered elements. A careful evaluation of the reaction mechanisms and the chemistry involved are required. The DRC allows the use of different gases, among them, ammonia (NH(3)), methane (CH(4)), hydrogen (H(2)) and oxygen (O(2)) are the most known, but there are other potentially useful gases like nitrous oxide (N(2)O), nitrogen oxide (NO), carbon dioxide (CO(2)), fluoromethane (CH(3)F), sulphur hexafluoride (SF(6)) and carbon disulfide (CS(2)). This paper provides a review on the analytical challenges for a reliable assay of As, Cr, Se and V by DRC-ICP-MS and illustrates different approaches and mechanisms involved in the analysis of polymers, biological fluids (serum, urine and whole blood), rock, soil and particulate matter.     

Palladium: a future key player in the nanomedical field?

Metal nanostructures offer invaluable possibilities for targeted drug delivery, detection/diagnosis and imaging. Whereas iron, gold, silver and platinum nanoarchitectures have largely dominated this field to date, several hurdles impede the widespread application of those nanopharmaceuticals in a clinical context. Therefore, technologies based on alternative metals are now being evaluated for their potential in medical applications. Palladium nanostructures are characterized by remarkable catalytic and optical properties. However, until recently, very few studies have taken advantage of these unique characteristics for applications in the biomedical field. Very recently, palladium nanostructures have been reported as prodrug activator, as photothermal agents and for anti-cancer/anti-microbial therapy. With only a handful of reports available, the pharmaceutical applications of palladium nanostructures reviewed here are in their infancy. Yet their interesting performance and toxicity profiles may qualify them as future key players in the nanomedical field.