Electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of trace amount of lanthanides and yttrium in soil with polytetrafluroethylene emulsion as a chemical modifier

A method of electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the determination of trace lanthanides and yttrium in soil samples with a polytetrafluorethylene (PTFE) emulsion as chemical modifier to promote the vaporization of the analytes from the graphite furnace was developed in this paper. The analytical characteristics, spectral interference and matrix effect of the analytical method were evaluated and critically compared with those of pneumatic nebulization inductively coupled plasma mass spectrometry (PN-ICP-MS). Under the optimized operation conditions, the relative detection limits of lanthanides (La-Lu) and yttrium for ETV-ICP-MS and PN-ICP-MS were 0.4-20 ng l⁻¹ and 1.0-21 ng l⁻¹, respectively, the absolute detection limits for ETV-ICP-MS were 4-200 fg, which were improved by 1-2 orders of magnitude compared with PN-ICP-MS. While the analytical precision of ETV-ICP-MS is worse than that of PN-ICP-MS, with the R.S.D.s (%) of 4.1-10% for the former and 2.9-7.8% for the latter. Regarding to the matrix effect, both conventional method and stepwise dilution method were employed to observe the effect of matrix and the very similar results were obtained. It was found that the highest tolerance concentration of the matrix is 1000 mg l⁻¹ and 800 mg l⁻¹ for ETV-ICP-MS and PN-ICP-MS, respectively. To assess the accuracy, the proposed method was applied to the determination of trace lanthanides and yttrium in three different soil standard reference materials and one soil sample, and the determined values are in good agreement with the certified values or reference values.     

Molecular absorption spectrometry in flames and furnaces: A review

Molecular absorption spectrometry (MAS), originally developed in the 1970s, is a technique to determine non-metals in flames and graphite furnaces by monitoring the absorbance of diatomic molecules. Early studies employed low resolution instruments designed for line source atomic absorption, which provided a limited choice of analytical wavelengths, insufficient spectral resolution, and spectral interferences. However, the development of high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) instrumentation has allowed the analysis of challenging samples for non-metals as well as some difficult elements to determine by AAS, such as aluminum and phosphorus. In this review, theory and analytical considerations for MAS are discussed. The principles and limitations of low resolution MAS are described, along with its applications. HR-CS AAS instrumentation is reviewed, emphasizing performance characteristics most relevant for MAS. Applications of flame and HR-CS GFMAS are reviewed, highlighting the most significant work to date. The paper concludes with an evaluation of the enhanced analytical capabilities provided by HR-CS MAS.     

Electrothermal vaporisation ICP-mass spectrometry (ETV-ICP-MS) for the determination and speciation of trace elements in solid samples - A review of real-life applications from the author's lab

The use of electrothermal vaporisation (ETV) from a graphite furnace as a means of sample introduction in inductively coupled plasma mass spectrometry (ICP-MS) permits the direct analysis of solid samples. A multi-step furnace temperature programme is used to separate the vaporisation of the target element(s) and of the matrix components from one another. Sometimes, a chemical modifier is used to enable a higher thermal pre-treatment temperature, by avoiding premature analyte losses (stabilisation) or promoting the selective volatilisation of matrix components. In almost all instances, accurate results can be obtained via external calibration or single standard addition using an aqueous standard solution. Absolute limits of detection are typically ~1 pg, which corresponds to 1 ng/g for a typical sample mass of 1 mg. Real-life applications carried out in the author's lab are used to illustrate the utility of this approach. These applications aim at trace element determination in industrial and environmental materials. The industrial materials analysed include different types of plastics - Carilon, polyethylene, poly(ethyleneterephtalate) and polyamide - and photo- and thermographic materials. As samples from environmental origin, plant material, animal tissue and sediments were investigated. Some applications aimed at a multi-element determination, while in other, the content of a single, but often challenging, element (e.g., Si or S) had to be measured. ETV-ICP-MS was also used in elemental speciation studies. Separation of Se-containing proteins was accomplished using polyacrylamide gel electrophoresis (PAGE). Subsequent quantification of the Se content in the protein spots was carried out using ETV-ICP-MS. As the volatilisation of methylmercury and inorganic mercury could be separated from one another with respect to time, no chromatographic or electrophoretic separation procedure was required, but ETV-ICP-MS as such sufficed for Hg speciation in fish tissue.     

Determination of refractory elements in atmospheric particulates using slurry sampling electrothermal vaporization inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry with polyvinylidene fluoride as chemical modifier

Electrothermal vaporization (ETV) inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) with polyvinylidene fluoride (PVDF) as chemical modifier are critically compared for the determination of refractory elements in coal fly ash and airborne particulates. The atmospheric particulates that collected on a PVDF filter were introduced into the graphite furnace in the form of a slurry by dissolving the filter in dimethylformamide, and the dissolved filter PVDF, along with additional added PVDF powder, was used as a chemical modifier for subsequent ETV-ICP-OES and ETV-ICP-MS determination. The vaporization behaviors of analytes (Ti, Zr, V, Mo, Cr, La) in ETV-ICP-OES/MS were studied in detail, and the optimal ETV operating parameters were obtained. Under the optimized operating conditions, the detection limits of target elements were 0.08-2.7 ng m(-3) for ETV-ICP-OES and 0.5-50 pg m(-3) for ETV-ICP-MS, respectively, with analytical precisions of 3.5-7.3% for ETV-ICP-OES and 3.9-9.6% for ETV-ICP-MS, respectively. The tolerable amounts of matrix elements for ETV-ICP-OES are higher than for ETV-ICP-MS. Both ETV-ICP-OES and ETV-ICP-MS were used to directly determine the trace refractory elements in coal fly ash and airborne particulates and the analytical results are comparable.     

Application of quality by design to the development of analytical separation methods

Recent pharmaceutical regulatory documents have stressed the critical importance of applying quality by design (QbD) principles for in-depth process understanding to ensure that product quality is built in by design. This article outlines the application of QbD concepts to the development of analytical separation methods, for example chromatography and capillary electrophoresis. QbD tools, for example risk assessment and design of experiments, enable enhanced quality to be integrated into the analytical method, enabling earlier understanding and identification of variables affecting method performance. A QbD guide is described, from identification of quality target product profile to definition of control strategy, emphasizing the main differences from the traditional quality by testing (QbT) approach. The different ways several authors have treated single QbD steps of method development are reviewed and compared. In a final section on outlook, attention is focused on general issues which have arisen from the surveyed literature, and on the need to change the researcher’s mindset from the QbT to QbD approach as an important analytical trend for the near future.

CE–MS for anionic metabolic profiling: An overview of methodological developments

The efficient profiling of highly polar and charged metabolites in biological samples remains a huge analytical challenge in metabolomics. Over the last decade, new analytical techniques have been developed for the selective and sensitive analysis of polar ionogenic compounds in various matrices. Still, the analysis of such compounds, notably for acidic ionogenic metabolites, remains a challenging endeavor, even more when the available sample size becomes an issue for the total analytical workflow. In this paper, we give an overview of the possibilities of capillary electrophoresis‐mass spectrometry (CE–MS) for anionic metabolic profiling by focusing on main methodological developments. Attention is paid to the development of improved separation conditions and new interfacing designs in CE–MS for anionic metabolic profiling. A complete overview of all CE–MS‐based methods developed for this purpose is provided in table format (Table 1) which includes information on sample type, separation conditions, mass analyzer and limits of detection (LODs). Selected applications are discussed to show the utility of CE–MS for anionic metabolic profiling, especially for small‐volume biological samples. On the basis of the examination of the reported literature in this specific field, we conclude that there is still room for the design of a highly sensitive and reliable CE–MS method for anionic metabolic profiling. A rigorous validation and the availability of standard operating procedures would be highly favorable in order to make CE–MS an alternative, viable analytical technique for metabolomics.     

Inductively coupled plasma-mass spectrometry for the determination of elements and elemental species in food: a review

Inductively coupled plasma-mass spectrometry (ICP-MS) has definitely emerged as a powerful technique for total element determination and as a sensitive and selective detector in hyphenated methods for speciation analyses of elements in foods. In this review, the analytical challenges of elemental analysis of food and agricultural matrixes are discussed and several applications are examined. Selected examples illustrate the analytical approaches being used so far to address specific issues in various areas of food and nutrition research. The applications discussed include studies on dietary intake, element metabolism in man, transfer of elements through the food chain, effects of food processing and domestic preparation, and authenticity and origin assessment. The use of ICP-MS in the field of analytical quality assurance, food control, evaluation of food contact materials, and radionuclide contamination is also examined. Finally, the hyphenated techniques with ICP-MS detection used for elemental speciation in food are reviewed, and an overview of the main applications currently in the literature is presented. Throughout, recent trends and analytical developments likely to have a major impact on food-related areas are highlighted.     

Application of surface plasmon resonance for the detection of carbohydrates,glycoconjugates, and measurement of the carbohydrate-specific interactions: A comparison with conventional analytical techniques. A critical review

Carbohydrates (glycans) and their conjugates with proteins and lipids contribute significantly to many biological processes. That makes these compounds important targets to be detected, monitored and identified. The identification of the carbohydrate content in their conjugates with proteins and lipids (glycoforms) is often a challenging task. Most of the conventional instrumental analytical techniques are time-consuming and require tedious sample pretreatment and utilising various labeling agents. Surface plasmon resonance (SPR) has been intensively developed during last two decades and has received the increasing attention for different applications, from the real-time monitoring of affinity bindings to biosensors. SPR does not require any labels and is capable of direct measurement of biospecific interaction occurring on the sensing surface. This review provides a critical comparison of modern analytical instrumental techniques with SPR in terms of their analytical capabilities to detect carbohydrates, their conjugates with proteins and lipids and to study the carbohydrate-specific bindings. A few selected examples of the SPR approaches developed during 2004–2011 for the biosensing of glycoforms and for glycan–protein affinity studies are comprehensively discussed.     

Recent update on use of ionic liquids for enzyme immobilization,activation, and catalysis: A partnership for sustainability

Recent literature survey suggested that, ionic liquid not only possesses potential as a green solvent, but also plays a significant role in enzyme immobilization, activation, stabilization, and catalysis. Furthermore, biocatalysis in ionic liquids (IL) may be a key sustainable solution for the next generation chemical processes, which requisite extensive research efforts to expand the knowledge horizons in this field. In view of this, the present review highlights the recent update of potential applications of IL in biocatalysis for (i) biomass pretreatment/hydrolysis, (ii) enzyme immobilization-activation, (iii) organic transformation, (iv) bioremediation, and (v) biosensing. Moreover, this review also addresses the challenging issues and future outlook of this research area for the industrial development in near future.     

Recent advances in upper rim functionalization of resorcin[4]arene derivatives: Synthesis and applications

Abstract

During the last decades, resorcin[4]arenes have drawn much attention in the field of supramolecular chemistry because of their practical applicability in different areas. Therefore, many scientists have investigated this class of derivatives in recent years. In this article, we comprehensively reviewed a brief literature survey on the chemistry of upper rim functionalization of calix[4]resorcinarene derivatives and their applications concerning optical chemosensors, liquid crystal materials, host-guest systems, catalysis, drug delivery, biological activities, and analytical applications. This short review describes the survey of literature synthesis and upper rim functionalization of resorcin[4]arenes and their different application published in the last six years (2015–2020).     

Solid-phase microextraction in pesticide residue analysis

The applications of solid-phase microextraction (SPME) for sample preparation in pesticide residue analysis are reviewed in this paper taking into account the different approaches of this technique coupled mainly to gas chromatography but also to high-performance liquid chromatography. A complete revision of the existing literature has been made considering the different applications divided according to the pesticide families (organochlorine, organophosphorus, triazines, thiocarbamates, substituted uracils, urea derivatives and dinitroanilines among others) and the sample matrices analysed which included environmental samples (water and soil), food samples and biological fluids. Details on the analytical characteristics of the procedures described in the reviewed papers are given, and new trends in the applications of SPME in this field are discussed.     

Electrochemical sensors and biosensors based on redox polymer/carbon nanotube modified electrodes: A review

The aim of this review is to present the contributions to the development of electrochemical sensors and biosensors based on polyphenazine or polytriphenylmethane redox polymers together with carbon nanotubes (CNT) during recent years. Phenazine polymers have been widely used in analytical applications due to their inherent charge transport properties and electrocatalytic effects. At the same time, since the first report on a CNT-based sensor, their application in the electroanalytical chemistry field has demonstrated that the unique structure and properties of CNT are ideal for the design of electrochemical (bio)sensors. We describe here that the specific combination of phenazine/triphenylmethane polymers with CNT leads to an improved performance of the resulting sensing devices, because of their complementary electrical, electrochemical and mechanical properties, and also due to synergistic effects. The preparation of polymer/CNT modified electrodes will be presented together with their electrochemical and surface characterization, with emphasis on the contribution of each component on the overall properties of the modified electrodes. Their importance in analytical chemistry is demonstrated by the numerous applications based on polymer/CNT-driven electrocatalytic effects, and their analytical performance as (bio) sensors is discussed.     

Dissimilar or orthogonal reversed-phase chromatographic systems: A comparison of selection techniques

Developing an analytical separation procedure for an unknown mixture is a challenging issue. An important example is the separation and quantification of a new drug and its impurities. One approach to start method development is the screening of the mixture on dissimilar chromatographic systems, i.e. systems with large selectivity differences. After screening, the most suited system is retained for further method development. In a step prior to such strategy dissimilar chromatographic systems need to be selected. In this paper the performance of different chemometric selection approaches, described in the literature, was visually evaluated and compared. Additionally, orthogonal projection approach (OPA) was tested as another potential selection method. All techniques, including the OPA method, were able to select (a set of) dissimilar chromatographic systems and many similarities between the selections were observed. However, the Kennard and Stone algorithm performed best in selecting the most dissimilar systems in the earliest steps of the selection procedure. The generalized pairwise correlation method (GPCM) and the auto-associative multivariate regression trees (AAMRT) were also performing well. OPA and weighted pair group method using arithmetic averages (WPGMA) are less preferable.     

Elemental labelling combined with liquid chromatography inductively coupled plasma mass spectrometry for quantification of biomolecules: A review

This article reviews novel quantification concepts where elemental labelling is combined with flow injection inductively coupled plasma mass spectrometry (FI-ICP-MS) or liquid chromatography inductively coupled plasma mass spectrometry (LC–ICP-MS), and employed for quantification of biomolecules such as proteins, peptides and related molecules in challenging sample matrices. In the first sections an overview on general aspects of biomolecule quantification, as well as of labelling will be presented emphasizing the potential, which lies in such methodological approaches. In this context, ICP-MS as detector provides high sensitivity, selectivity and robustness in biological samples and offers the capability for multiplexing and isotope dilution mass spectrometry (IDMS). Fundamental methodology of elemental labelling will be highlighted and analytical, as well as biomedical applications will be presented. A special focus will lie on established applications underlining benefits and bottlenecks of such approaches for the implementation in real life analysis. Key research made in this field will be summarized and a perspective for future developments including sophisticated and innovative applications will given.     

High Performance Liquid Chromatography (HPLC) with Fluorescence Detection for Quantification of Steroids in Clinical,Pharmaceutical, and Environmental Samples: A Review

Steroids are compounds widely available in nature and synthesized for therapeutic and medical purposes. Although several analytical techniques are available for the quantification of steroids, their analysis is challenging due to their low levels and complex matrices of the samples. The efficiency and quick separation of the HPLC combined with the sensitivity, selectivity, simplicity, and cost-efficiency of fluorescence, make HPLC coupled to fluorescence detection (HPLC-FLD) an ideal tool for routine measurement and detection of steroids. In this review, we covered HPLC-FLD methods reported in the literature for the steroids quantification in clinical, pharmaceutical, and environmental applications, focusing on the various approaches of fluorescent derivatization. The aspects related to analytical methodology including sample preparation, derivatization reagents, and chromatographic conditions will be discussed.     

Applications of polydimethylsiloxane in analytical chemistry: A review

Silicones have innumerable applications in many areas of life. Polydimethylsiloxane (PDMS), which belongs to the class of silicones, has been extensively used in the field of analytical chemistry owing to its favourable physicochemical properties. The use of PDMS in analytical chemistry gained importance with its application as a stationary phase in gas chromatographic separations. Since then it has been used in many sample preparation techniques such as solid phase microextraction (SPME), stir bar sorptive extraction (SBSE), thin-film extraction, permeation passive sampling, etc. Further, it is gaining importance in the manufacturing of lab-on-a-chip devices, which have revolutionized bio-analysis. Applications of devices containing PDMS and used in the field of analytical chemistry are reviewed in this paper.     

高效液相色谱-电感耦合等离子体质谱联用技术用于环境中元素形态分析的最新进展

综述了高效液相色谱-电感耦合等离子体质谱(HPLC-ICP-MS)联用技术在环境科学中的应用情况.参考过去十年内的国内外文献,从方法学的角度论述了HPLC联用ICP-MS技术的发展,重点探讨了该技术在环境领域,尤其是在元素形态分析(包括生物学,生物无机化学和生物医学)中的应用.     

Shaping and exploring the micro- and nanoworld using bipolar electrochemistry

Bipolar electrochemistry is a technique with a rather young history in the field of analytical chemistry. Being based on the polarization of a conducting object which is exposed to an external electric field, it allowed recently the development of new methods for controlled surface modification at the micro- and nanoscale and very original analytical applications. Using bipolar electrodes, analyte separation and detection becomes possible based on miniaturized systems. Moreover, the modified objects that can be created with bipolar electrochemistry could find applications as key components for detection systems. In this contribution, the principles of bipolar electrochemistry will be reviewed, as well as recent developments that focus on the modification of objects at the nano- and microscale and their potential application in miniaturized analytical systems.     

Enantiomeric separations by means of nano‐LC

Enantiomers represent a class of compounds extensively investigated since they can show totally different behaviors when they interact with a chiral environment. Because of their identical chemical structure (they differ only in the spatial arrangement of the atoms in the molecule), the separation of optical isomers is a challenging task of analytical chemistry. So far employed methods for the separation of enantiomers are mainly based on chromatography. CE as well was considered as an analytical technique suitable for chiral separations, characterized by high efficiency and low consumption of reagent. Recently, miniaturization was introduced in LC to answer the needs to perform analyses in the minimum time, to use the smallest amount of samples and to reduce environmental pollution. Nano‐LC represents nowadays a valid alternative to the abovementioned conventional analytical techniques, and can be advantageously exploited for enantiomeric separation especially because it needs minute amounts of the chiral material necessary to carry out enantiomeric separations. This review describes the development and applications of nano‐LC in the field of chiral separations. The data reported in literature show its relevance for the study enantiomers‐chiral selectors interaction, as well as for application in pharmaceutical and clinical research.