Electrochemical methods of analysis of inorganic substances. Publications for 1990–1999

The data of the scientometric study of publications in inorganic electrochemical analysis for 1990– 1999 were presented. Most of the published papers (from 60 to 80%) deal with voltammetry and potentiometry. Since 1997, the number of papers on voltammetry has been higher or equal to the number of papers on potentiometry, which is due to the successive development of modified electrodes, the use of ultramicroelectrodes, and the development of stripping voltammetry, including adsorption voltammetry. The role of electrochemical analysis in the development and production of sensors was discussed. The most advantageous methods are potentiometry and conductometry; the role of amperometry is also significant. It was underlined that, although the number of papers on coulometry is low, this method is the most precise absolute method of analytical chemistry. The contribution of conferences on analytical chemistry to the publications on electrochemical methods and the elements leading in the number of publications are considered. Presented at the V All-Russian Conference with the Participation of CIS Countries on Electrochemical Methods of Analysis (EMA-99), Moscow, December 6–8,1999.     

Opportunities for innovation in neutron activation analysis

Neutron activation laboratories worldwide are at a turning point at which new staff has to be found for the retiring pioneers from the 1960s–1970s. A scientific career in a well-understood technique, often characterized as ‘mature’ may only be attractive to young scientists if still challenges for further improvement and inspiring new applications can be offered. The strengths and weaknesses of neutron activation analysis (NAA) are revisited to identify opportunities for innovation. Position-sensitive detection of elements in large samples, Monte Carlo calculations replacing the use of standards, use of scintillator detectors and new deconvolution techniques for increasing the sensitivity are examples of challenging new roads in NAA. Material science provides challenges for the application of NAA in both bulk samples, ultrathin layers and ultrapure materials.     

Plutonium and americium concentrations and vertical profiles in some Italian mosses used as bioindicators

We have examined the uptake of actinide elements Am and, Pu by different species of lichen and moss collected in two locations (Urbino, Central Italy; Alps region, North-east Italy). Plutonium and americium were separated and determined by extraction chromatography, electrodeposition and alpha-spectrometry. This paper summarizes our results with a special emphasis on the vertical profiles of these actinides in two different species of mosses. Several 1–2 cm depth sections were obtained and dated by²¹⁰Pb method. A typical peak for^239,240Pu and²⁴¹Am was found in the very old moss species (“Sphagnum Compactum”) at a depth corresponding to the period 1960–1970 which was the period characterized by the maximum nuclear weapon tests. In a younger moss species (“Neckeria Crispa”) no peak was observed and the regression curves showed that Am is more mobile than^239,240Pu and²³⁸Pu.     

Immuno-affinity columns versus conventional clean-up: a method-comparison study for the determination of zearalenone in corn

The efficiency of a modern analytical method employing immuno-affinity columns (IACs) is compared to a well established traditional technique with respect to the determination of zearalenone (ZON) in corn in the μg/kg range. Despite of a constant error of about 4 μg/kg in the examined working range of 10–200 μg/kg, analytical data obtained from the analysis of spiked and naturally contaminated samples showed good correspondence for the compared methods. The performance characteristics of immuno-affinity-chromatography as a new clean-up technique for the determination of ZON in corn is reported for the first time and compared to a conventional clean-up procedure Received: 25 March 1997 / Revised: 5 May 1997 / Accepted: 12 May 1997     

Electrocatalytic oxidation of methanol and other short chain aliphatic alcohols at Ni(II)–quercetin complex modified multi-wall carbon nanotube paste electrode

A modified electrode Ni(II)–Qu–MWCNT-PE has been fabricated by electrodepositing nickel(II)–quercetin [Ni(II)–Qu] complex on the surface of multi-wall carbon nanotube paste electrode (MWCNT-PE) in alkaline solution. Ni(II)–Qu–MWCNT-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple compared with Ni(II)–MWCNT-PE and Ni(II)–Qu-carbon paste electrode. It also shows electrocatalytic activity toward the oxidation of methanol and other short chain aliphatic alcohols, such as ethanol, 1-propanol, and 1-butanol. The catalytic peak current and peak potential decrease in exponential form with the increase of carbon number of the chains. Kinetic parameters such as the electron transfer coefficient, α, rate constant, k _s, of the electrode reaction, and the catalytic rate constant, k _cat, for oxidation of methanol are determined. The stability and reproducibility of the Ni(II)–Qu–MWCNT-PE are good for practical applications.     

Electroactive films of interpolymer complexes of polyaniline with polyamidosulfonic acids: advantageous features in some possible applications

With the purpose of determining prospects of possible applications of interpolymer complexes of polyaniline (PANI) with poly(amidosulfonic acid)s, we have performed a comparative study of polyaniline films prepared by electrochemical polymerization of aniline in the presence of the polyacids distinguished by different rigidities of the polymer backbone: (1) poly(2-acrylamido-2-methyl-1-propanosulfonic acid) (flexible backbone); (2) poly-p,p′-(2,2′-disulfoacid)-diphenylen-iso-phthalamid (semi-rigid backbone); (3) poly-p,p′-(2,2′-disulfoacid)-diphelylen-tere-phthalamid (rigid backbone); and (4) a copolymer of the latter two acids with monomer feed ratio 1:1 (co-PASA). Spectroelectrochemical studies in the UV–vis–NIR range showed that PANI complexes with rigid-chain polyacids far more effectively modulate absorbance in the Vis–NIR range and can be considered as promising candidates for “smart windows” development. Due to the presence of bulky unmovable polyacid anion, PANI interpolymer complexes (particularly those with the semi-rigid-chain polyacids) possess much wider pH range of electroactivity than common PANI, which is of great importance for biosensor applications. The interpolymer complexes with flexible-chain and semi-rigid-chain polyacids exhibit good optical response to ammonia vapors at conditions of high humidity, which make them promising materials for the development of ammonia optical sensors.     

Research in an emerging “big science” discipline: the case of neutron scattering in Spain

Neutron scattering (NS) is a “big science” discipline whose research spans over a wide spectrum of fields, from fundamental or basic science to technological applications. The objective of this paper is to track the evolution of Spanish research in NS from a bibliometric perspective and to place it in the international context. Scientific publications of Spanish authors included in the Web of Science (WoS 1970–2006) are analysed with respect to five relevant dimensions: volume of research output, impact, disciplinary diversity, structural field features and internationalisation. NS emerges as a highly internationalised fast-growing field whose research is firmly rooted in Physics, Chemistry and Engineering, but with applications in a wide range of fields. International collaboration links -present in around 70% of the documents- and national links have largely contributed to mould the existing structure of research in the area, which evolves around major neutron scattering facilities abroad. The construction of a new European neutron source (ESS) would contribute to the consolidation of the field within the EU, since it will strengthen research and improve current activity.     

Trace analysis of high-purity graphite by LA–ICP–MS

Laser-ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) has been established as a very efficient and sensitive technique for the direct analysis of solids. In this work the capability of LA–ICP–MS was investigated for determination of trace elements in high-purity graphite. Synthetic laboratory standards with a graphite matrix were prepared for the purpose of quantifying the analytical results. Doped trace elements, concentration 0.5 μg g^–1, in a laboratory standard were determined with an accuracy of 1% to ± 7% and a relative standard deviation (RSD) of 2–13%. Solution-based calibration was also used for quantitative analysis of high-purity graphite. It was found that such calibration led to analytical results for trace-element determination in graphite with accuracy similar to that obtained by use of synthetic laboratory standards for quantification of analytical results. Results from quantitative determination of trace impurities in a real reactor-graphite sample, using both quantification approaches, were in good agreement. Detection limits for all elements of interest were determined in the low ng g^–1 concentration range. Improvement of detection limits by a factor of 10 was achieved for analyses of high-purity graphite with LA–ICP–MS under wet plasma conditions, because the lower background signal and increased element sensitivity. Received: 4 January 2001 / Revised: 27 March 2001 / Accepted: 28 March 2001     

Progress in direct solid sampling analysis using line source and high-resolution continuum source electrothermal atomic absorption spectrometry

The literature about direct solid sample analysis of the past 10–15 years using electrothermal atomic absorption spectrometry has been reviewed. It was found that in the vast majority of publications aqueous standards were reported as having been used for calibration after careful program optimization. This means the frequently expressed claim that certified reference materials with a matrix composition and analyte content close to that of the sample have to be used for calibration in solid sample analysis is not confirmed in the more recent literature. There are obviously limitations, and there are examples in the literature where even calibration with certified reference materials did not lead to accurate results. In these cases the problem is typically associated with spectral interferences that cannot be corrected properly by the systems available for conventional line source atomic absorption spectrometry, including Zeeman-effect background correction. Using high-resolution continuum source atomic absorption spectrometry, spectral interferences become visible owing to the display of the spectral environment at both sides of the analytical line at high resolution, which makes program optimization straightforward. Any spectrally continuous background absorption is eliminated automatically, and even rapidly changing background absorption does not cause any artifacts, as measurement and correction of background absorption are truly simultaneous. Any kind of fine-structured background can be eliminated by “subtracting” reference spectra using a least-squares algorithm. Aqueous standards are used for calibration in all published applications of high-resolution continuum source atomic absorption spectrometry to direct solid sample analysis. This contribution is based on a presentation given at the Colloquium for Analytical Atomic Spectroscopy (CANAS ‘07) held March 18–21, 2007 in Constance, Germany.     

New tools: Uncertainty-based data evaluation

 The principles of uncertainty-based data evaluation are explained. Based on a brief review of recent publications on the topic, examples for application to standard procedures in analytical chemistry – calibration, method validation, standard addition etc., – are given. The performance and the advantages of uncertainty-based data evaluation are discussed. Received: 4 July 1998 · Accepted: 6 July 1998     

Bibliometric analysis of scientific publications on fluoropolymers

Scientific publications on fluoropolymers are sought in the Chemical Abstracts Plus database accessed via the SciFinder system. For the period 1946–2010, nearly 116 000 publications containing the search term fluoropolymers as the main concept are found. For nearly 75 000 publications over the period 2000–2009, a detailed bibliometric analysis is performed on the basis of thematic sections and subject headings of the database, substances, publication types, languages and authors of publications, journal titles, and organization names. On the basis of the results, recommendations for improving Russian indicators in the field of fluoropolymers are suggested.     

Optimisation of a selective method for the determination of organophosphorous triesters in outdoor particulate samples by pressurised liquid extraction and large-volume injection gas chromatography–positive chemical ionisation–tandem mass spectrometry

A selective analytical method for the determination of nine organophosphate triesters and triphenylphosphine oxide (TPPO) in outdoor particulate matter is presented. It involves a fully automated pressurised liquid extraction (PLE) step, integrating an alumina clean-up process, and subsequent determination by large-volume injection gas chromatography–positive chemical ionisation–tandem mass spectrometry (LVI-GC–PCI–MS/MS). The extraction variables (solvent, amount of adsorbent, temperature, time and number of cycles) were optimised using a multicriteria strategy which implements a desirability function that maximises both extraction and clean-up efficiencies while searching for the best-compromise PLE conditions. The final method affords quantification limits of between 0.01 and 0.3 μg g⁻¹ and recoveries of >80%, with the exceptions of the most polar analytes, TCEP and TPPO (~65%) for both urban dust and PM10 samples. Moreover, the method permitted the levels of these compounds in dust deposited outdoors (between LOD and 0.5 μg g⁻¹ for TEHP) and PM10 samples (between LOD and 2.4 μg m⁻³ for TiBP) to be measured and reported for the first time. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Improving Liquid Chromatography-Mass Spectrometry Sensitivity Using a Subambient Pressure Ionization with Nanoelectrospray (SPIN) Interface

In this work, the subambient pressure ionization with nanoelectrospray (SPIN) ion source and interface, which operates at ~15–30 Torr, is demonstrated to be compatible with gradient reversed-phase liquid chromatography-MS applications, exemplified here with the analysis of complex samples (a protein tryptic digest and a whole cell lysate). A low liquid chromatographic flow rate (100–400 nL/min) allowed stable electrospray to be established while avoiding electrical breakdown. Efforts to increase the operating pressure of the SPIN source relative to previously reported designs prevented solvent freezing and enhanced charged cluster/droplet desolvation. A 5- to 12-fold improvement in sensitivity relative to a conventional atmospheric pressure nanoelectrospray ionization (ESI) source was obtained for detected peptides.     

Trace analysis of environmental matrices by large-volume injection and liquid chromatography–mass spectrometry

The time-honored convention of concentrating aqueous samples by solid-phase extraction (SPE) is being challenged by the increasingly widespread use of large-volume injection (LVI) liquid chromatography–mass spectrometry (LC–MS) for the determination of traces of polar organic contaminants in environmental samples. Although different LVI approaches have been proposed over the last 40 years, the simplest and most popular way of performing LVI is known as single-column LVI (SC-LVI), in which a large-volume of an aqueous sample is directly injected into an analytical column. For the purposes of this critical review, LVI is defined as an injected sample volume that is ≥10% of the void volume of the analytical column. Compared with other techniques, SC-LVI is easier to set up, because it requires only small hardware modifications to existing autosamplers and, thus, it will be the main focus of this review. Although not new, SC-LVI is gaining acceptance and the approach is emerging as a technique that will render SPE nearly obsolete for many environmental applications. In this review, we discuss: the history and development of various forms of LVI; the critical factors that must be considered when creating and optimizing SC-LVI methods; and typical applications that demonstrate the range of environmental matrices to which LVI is applicable, for example drinking water, groundwater, and surface water including seawater and wastewater. Furthermore, we indicate direction and areas that must be addressed to fully delineate the limits of SC-LVI.     

Recent trends in trace element determination and speciation using inductively coupled plasma mass spectrometry

During the past decade, inductively coupled plasma mass spectrometry (ICPMS) has evolved from a delicate research tool, intended for the well-trained scientist only, into a more robust and well-established analytical technique for trace and ultra-trace element determination, with a few thousand of instruments used worldwide. Despite this immense success, it should be realized that in its ’standard configuration’– i.e. equipped with a pneumatic nebulizer for sample introduction and with a quadrupole filter – ICPMS also shows a number of important limitations and disadvantages: (i) the occurrence of spectral interferences may hamper accurate trace element determination, (ii) solid samples have to be taken into solution prior to analysis and (iii) no information on the ‘chemical form’ in which an element appears can be obtained. Self-evidently, efforts have been and still are made to overcome the aforementioned limitations to the largest possible extent. The application of a double focusing sector field mass spectrometer in ICPMS instrumentation offers a higher mass resolution, such that spectral overlap can be avoided to an important extent. Additionally, in a sector field instrument, photons are efficiently eliminated from the ion beam, resulting in very low background intensities, making it also very well-suited for extreme trace analysis. Also the combination of the ICP as an ion source and a quadrupole filter operated in a so-called ‘alternate’ stability region, an ion trap or a Fourier transform ion cyclotron resonance mass spectrometer allows high(er) mass resolution to be obtained. With modern quadrupole-based instruments, important types of spectral interferences can be avoided by working under ‘cool plasma’ conditions or by applying a collision cell. The use of electrothermal vaporization (ETV) or especially laser ablation (LA) for sample introduction permits direct analysis of solid samples with sufficient accuracy for many purposes. The application range of LA-ICPMS has become very wide and the introduction of UV lasers has led to an improved spatial resolution. Solid sampling ETV-ICPMS on the other hand can be used for some specific applications only, but accurate calibration is more straightforward than with LA-ICPMS. Limited multi-element capabilities, resulting from the transient signals observed with ETV or single shot LA, can be avoided by the use of a time-of-flight (TOF) ICPMS instrument. Finally, when combined with a powerful chromatographic separation technique, an ICP-mass spectrometer can be used as a highly sensitive, element-specific multi-element detector in elemental speciation studies. Especially liquid (HPLC-ICPMS) and – to a lesser extent – gas (GC-ICPMS) chromatography have already been widely used in combination with ICPMS. In speciation work, sample preparation is often observed to be troublesome and this aspect is presently receiving considerable attention. For GC-ICPMS, new sample pretreatment approaches, such as headspace solid phase microextraction (headspace SPME) and the purge-and-trap technique have been introduced. Also supercritical fluid chromatography (SFC) and capillary electrophoresis (CE) show potential to be of use in combination with ICPMS, but so far the application ranges of SFC-ICPMS and CE-ICPMS are rather limited. It is the aim of the present paper to concisely discuss the aforementioned recent ’trends’ in ICPMS, using selected real-life applications reported in the literature. Received: 30 November 1998 / Revised: 22 March 1999 / Accepted: 24 March 1999     

Relevance and use of capillary coatings in capillary electrophoresis–mass spectrometry

Over the last two decades, coupled capillary electrophoresis (CE)–mass spectrometry (MS) has developed into a generally accepted technique with a wide applicability. A growing number of CE-MS applications make use of capillaries where the internal wall is modified with surface coating agents. In CE-MS, capillary coatings are used to prevent analyte adsorption and to provide appropriate conditions for CE-MS interfacing. This paper gives an overview of the various capillary coating strategies used in CE-MS. The main attention is devoted to the way coatings can contribute to a proper CE-MS operation. The foremost capillary coating methods are discussed with emphasis on their compatibility with MS detection. The role of capillary coatings in the control of the electroosmotic flow and the consequences for CE-MS coupling are treated. Subsequently, an overview of reported applications of CE-MS employing different coating principles is presented. Selected examples are given to illustrate the usefulness of the coatings and the overall applicability of the CE-MS systems. It is concluded that capillary coatings can enhance the performance and stability of CE-MS systems, yielding a highly valuable and reproducible analytical tool.     

From single to multiple microcoil flow probe NMR and related capillary techniques: a review

Nuclear magnetic resonance (NMR) spectroscopy is one of the most important and powerful instrumental analytical techniques for structural elucidation of unknown small and large (complex) isolated and synthesized compounds in organic and inorganic chemistry. X-ray crystallography, neutron scattering (neutron diffraction), and NMR spectroscopy are the only suitable methods for three-dimensional structure determination at atomic resolution. Moreover, these methods are complementary. However, by means of NMR spectroscopy, reaction dynamics and interaction processes can also be investigated. Unfortunately, this technique is very insensitive in comparison with other spectrometric (e.g., mass spectrometry) and spectroscopic (e.g., infrared spectroscopy) methods. Mainly through the development of stronger magnets and more sensitive solenoidal microcoil flow probes, this drawback has been successfully counteracted. Capillary NMR spectroscopy increases the mass-based sensitivity of the NMR spectroscopic analysis up to 100-fold compared with conventional 5-mm NMR probes, and thus can be coupled online and off-line with other microseparation and detection techniques. It offers not only higher sensitivity, but in many cases provides better quality spectra than traditional methods. Owing to the immense number of compounds (e.g., of natural product extracts and compound libraries) to be examined, single microcoil flow probe NMR spectroscopy will soon be far from being sufficiently effective as a screening method. For this reason, an inevitable trend towards coupled microseparation–multiple microcoil flow probe NMR techniques, which allow simultaneous online and off-line detection of several compounds, will occur. In this review we describe the current status and possible future developments of single and multiple microcoil capillary flow probe NMR spectroscopy and its application as a high-throughput tool for the analysis of a large number of mass-limited samples. The advantages and drawbacks of different coupled microseparation–capillary NMR spectroscopy techniques, such as capillary high-performance liquid chromatography–NMR spectroscopy, capillary electrophoresis–NMR spectroscopy, and capillary gas chromatography–NMR spectroscopy, are discussed and demonstrated by specific applications. Another subject of discussion is the progress in parallel NMR detection techniques. Furthermore, the applicability and mixing capability of tiny reactor systems, termed “microreactors” or “micromixers,” implemented in NMR probes is demonstrated by carbamate- and imine-forming reactions.     

Supercritical fluid extraction combined with solid phase extraction as sample preparation technique for the analysis of β-blockers in serum and urine

A method is developed for the determination of β-blockers in serum and urine at levels of 0.5 μg/mL. The technique uses a combination of solid phase extraction (SPE) with in situ derivatization and supercritical fluid extraction (SFE) with subsequent gas chromatography mass spectrometry. The optimization of the SFE step shows that a static extraction period can be eliminated. The method gives good linearity (r = 0.991–0.999) and repeatability in the concentration range of 0.5 to 5 μg/mL. Relative standard deviations for oxprenolol, propanolol and metoprolol were less than 5% in serum and 5–11% in urine. Received: 23 May 1997 / Revised: 28 July 1997 / Accepted: 5 August 1997     

Analytical science – a discipline between chemistry and metrology

After Karel Eckschlager (Prague) introduced information theory into analytical chemistry in the mid 60s, its usage and importance to the discipline has grown exponentially. One wonders whether it is the chicken or the egg in this case as well, but without informatics the immense amount of data produced in analytical measurements today could not be digested, filtered, and understood. Klaus Doerffel (Deceased, formerly of Leipzig) was an active and driving participant in the development of informatics and its use in analytical chemistry. He has summarized the field up to 1995 in a work entitled: “Analytical science – A discipline between chemistry and metrology.” The work is too large to permit full publication in this journal. Therefore, the important points are summarized here, and the full text can be obtained by written request to the Editorial Office. Received: 10 February 1998 / Accepted: 12 February 1998     

Isocratic liquid chromatographic determination of three paraben preservatives in hygiene wipes using a reversed phase core-shell narrow-bore column

The first HPLC method for the separation of three paraben preservatives (methyl-, ethyl- and propyl parabens) using a core-shell analytical column is reported in this study. The separation was completed in less than 8 min at a low flow rate of 0.4 mL min⁻¹ and an isocratic mobile phase containing 20% acetonitrile as organic modifier. The backpressure was < 200 bar in all cases, enabling the usage of conventional HPLC equipment. The proposed analytical procedure was validated for linearity (0.5–20 μg L⁻¹), limits of detection (15–43 μg L⁻¹) and quantification (50–142 μg L⁻¹), selectivity, within day (1.3–1.5%) and day-to-day (3.4–4.6%) precision and accuracy. The proposed method has been applied to the determination of the selected paraben preservatives in commercially available hygiene wipes. The mean percent recoveries were found to be in the range of 98.0–98.4%.