Doubling the Carbonate-Binding Capacity of Nanojars by the Formation of Expanded Nanojars

Anion binding and extraction from solutions is currently a dynamic research topic in the field of supramolecular chemistry. A particularly challenging task is the extraction of anions with large hydration energies, such as the carbonate ion. Carbonate-binding complexes are also receiving increased interest due to their relevance to atmospheric CO₂ fixation. Nanojars are a class of self-assembled, supramolecular coordination complexes that have been shown to bind highly hydrophilic anions and to extract even the most hydrophilic ones, including carbonate, from water into aliphatic solvents. Here we present an expanded nanojar that is able to bind two carbonate ions, thus doubling the previously reported carbonate-binding capacity of nanojars. The new nanojar is characterized by detailed single-crystal X-ray crystallographic studies in the solid state and electrospray ionization mass spectrometric (including tandem MS/MS) studies in solution.     

Fluidized-bed extraction of polycyclic aromatic hydrocarbons from contaminated soil samples

Summary Due to the carcinogenity and ubiquity of polycyclic aromatic hydrocarbons in the environment they are of ongoing interest to analytical chemistry. In this study, a comparison of the classic Soxhlet extraction and, fluidized-bed extraction, has been conducted. The extraction of polycyclic aromatic hydrocarbons by this technique has been optimized considering as experimental variables the variation of the number of extraction cycles and the holding time after reaching the heating temperature by means of a surface response design. The significance of the operational parameters of the fluidized-bed extraction on the performance characteristics has been investigated. For the determination of the analytes a selective clean-up of the extracts followed by a fast gas chromatography method with mass spectrometric detection was used, resulting in low limits of detection (0.2 pg μL⁻¹). The accuracy of the complete analytical method was established by extraction and analysis of reference materials.     

Extraction of perfluorinated compounds from food matrices using fluorous solvent partitioning

Perfluorinated compounds (PFCs) such as perfluorooctane sulfonic acid (PFOS) have emerged as a new class of global environmental pollutant; they bioaccumulate and are persistent in the environment and in wildlife. Fluorine-fluorine interactions have been investigated as a means to isolate PFCs for mass spectrometric quantification. A novel sample extraction and cleanup procedure has been developed for fat-containing samples based on fluorous liquid-liquid extraction (F-LLE) in a triphasic solvent system consisting of hybrid:fluorous:organic solvent (trifluoroethanol:perfluorohexane/dichloromethane-saturated with water). This system partially separates fluorous from non-fluorous compounds, allowing removal of co-extractants, which had previously resulted in liquid chromatography mass spectrometry (LC-MS/MS) peak suppression preventing low-level detection of PFCs. The developed F-LLE was coupled with an existing extraction protocol allowing the limits of detection of PFCs to be lowered an order of magnitude for high fat samples. The developed workflow was used to show the absence of a range of eleven PFCs in nine UK and one Irish cheese samples. This representative application demonstrates a new application of fluorous-organic extraction in sample cleanup for measurement of fluorinated analytes in food, environment and broader analytical chemistry.     

Thin layer chromatography/mass spectrometry

Thin layer chromatography (TLC)--a simple, cost-effective, and easy-to-operate planar chromatographic technique--has been used in general chemistry laboratories for several decades to routinely separate chemical and biochemical compounds. Traditionally, chemical and optical methods are employed to visualize the analyte spots on the TLC plate. Because direct identification and structural characterization of the analytes on the TLC plate through these methods are not possible, there has been long-held interest in the development of interfaces that allow TLC to be combined with mass spectrometry (MS)--one of the most efficient analytical tools for structural elucidation. So far, many different TLC-MS techniques have been reported in the literature; some are commercially available. According to differences in their operational processes, the existing TLC-MS systems can be classified into two categories: (i) indirect mass spectrometric analyses, performed by scraping, extracting, purifying, and concentrating the analyte from the TLC plate and then directing it into the mass spectrometer's ion source for further analysis; (ii) direct mass spectrometric analyses, where the analyte on the TLC plate is characterized directly through mass spectrometry without the need for scraping, extraction, or concentration processes. Conventionally, direct TLC-MS analysis is performed under vacuum, but the development of ambient mass spectrometry has allowed analytes on TLC plates to be characterized under atmospheric pressure. Thus, TLC-MS techniques can also be classified into two other categories according to the working environment of the ion source: vacuum-based TLC-MS or ambient TLC-MS. This review article describes the state of the art of TLC-MS techniques used for indirect and direct characterization of analytes on the surfaces of TLC plates.     

基于喹啉和三唑环的开链冠醚对金属离子的选择传感

本文通过Click化学反应合成了一种含喹啉基和三唑基的开链冠醚, 考察和比较了主体化合物对镉等金属离子的荧光传感和选择性键合行为, 并通过荧光和核磁等手段研究了溶剂对其荧光传感的影响.     

Mass spectrometry applied to the analysis of estrogens in the environment

Environmental analytical chemistry has recently changed focus from analysis of non-polar, persistent contaminants (e.g. polychlorinated biphenyls and dioxins) to more polar and labile compounds that interfere with biological processes. For example, natural and synthetic estrogens and their metabolites have been detected in sewage treatment plant effluents at nanogram/liter concentrations that are similar to those at which both total sex reversal and intersex (containing both testes and ova) is induced in fish exposed to these compounds in laboratory experiments. The development of techniques for the analysis of natural and synthetic estrogens in biological fluids (i.e. serum and urine) has been a priority in the biomedical field. However, the recent recognition that estrogen hormones are contaminants in the environment that may contribute to endocrine disruption has focused attention on the need for highly sensitive and specific techniques that are applicable for trace analysis in complex environmental matrices. Three optimized mass spectrometric protocols have been developed for the determination and quantitation of steroid hormones in environmental matrices using gas chromatography/tandem mass spectrometry (GC/MS/MS), liquid chromatography/mass spectrometry selected ion monitoring, (LC/MS - SIM) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The advantages and disadvantages of each method are presented.     

Ultra-high performance liquid chromatography tandem mass spectrometry for comprehensive analysis of urinary acylcarnitines

We report an enabling mass spectrometric method for the analysis of lipid metabolites in order to define better the lipid metabolome in terms of chemical diversity and generate fragment ion spectra of these metabolites as a potential resource for unknown metabolite identification. This work focuses on the analysis of one important class of lipid metabolites, the acylcarnitines. Current analytical methods have only detected and identified a limited number of these metabolites. The method described herein provides the most comprehensive acylcarnitine profile in urine of healthy individuals up to date. It involves an optimized solid phase extraction technique for selective analyte extraction using cartridges containing both lipophilic and cation-exchange properties. The captured analytes are then subjected to ultra-high performance liquid chromatography (UPLC) separation, followed by tandem mass spectrometry (MS/MS) analysis using information-dependent acquisitions and selected reaction monitoring (SRM). The urine of six healthy individuals was analyzed using this method. A total of 355 acylcarnitines were detected; only 43 of them have been previously reported in the urine of healthy individuals. Detection of this large number of acylcarnitines illustrates the great diversity of the lipid metabolome as well as the usefulness of the method for profiling acylcarnitines. Furthermore, the MS/MS spectra of the 355 acylcarnitines will be uploaded to a public human metabolome database as a mass spectrometric resource for unknown metabolite identification.     

Mass spectrometry and combinatorial chemistry: a short outline.

The rapid evolution of combinatorial chemistry in recent years has led to a dramatic improvement in synthetic capabilities. The goal is to accelerate the discovery of molecules showing affinity against a target, such as an enzyme or a receptor, through the simultaneous synthesis of a great number of structurally diverse compounds. This is done by generating combinatorial libraries containing as many as hundreds or thousands of compounds. The need to test all these compounds led to the development of high-throughput screening (HTS) techniques, and also high-throughput analytical techniques capable of assessing the occurrence, structure and purity of the products. In order to be applied effectively to the characterization of combinatorial libraries, an analytical technique must be adequately sensitive (to analyse samples which are typically produced in nanomole amounts or less), fast, affordable and easy to automate (to minimize analysis time and operator intervention). Although no method alone can meet all the analytical challenges underlying this task, the recent progress in mass spectrometric (MS) instrumentation renders this technique an essential tool for scientists working in this area. We describe here relevant aspects of the use of MS in combinatorial technologies, such as current methods of characterization, purification and screening of libraries. Some examples from our laboratory deal with the analysis of pooled oligomeric libraries containing n x 324(n = 1, 2) compounds, using both on-line high-performance liquid chromatography/MS with an ion trap mass spectrometer, and direct infusion into a triple quadrupole instrument. In the first approach, MS and product ion MS/MS with automatic selection of the precursor were performed in one run, allowing library confirmation and structural elucidation of unexpected by-products. The second approach used MS scans to characterize the entire library and also precursor ion and neutral loss scans to detect selectively components with given structural characteristics.     

Advances in Anion Supramolecular Chemistry: From Recognition to Chemical Applications

Since the start of this millennium, remarkable progress in the binding and sensing of anions has been taking place, driven in part by discoveries in the use of hydrogen bonding, as well as the previously under‐exploited anion–π interactions and halogen bonding. However, anion supramolecular chemistry has developed substantially beyond anion recognition, and now encompasses a diverse range of disciplines. Dramatic advance has been made in the anion‐templated synthesis of macrocycles and interlocked molecular architectures, while the study of transmembrane anion transporters has flourished from almost nothing into a rapidly maturing field of research. The supramolecular chemistry of anions has also found real practical use in a variety of applications such as catalysis, ion extraction, and the use of anions as stimuli for responsive chemical systems.     

Methodological aspects of an off‐line combination of preparative isotachophoresis and high‐performance liquid chromatography with mass spectrometry in the analysis of biological matrices

This work reports on some methodological aspects of an off‐line combination of preparative ITP and HPLC with mass spectrometric detection (pITP‐HPLC‐MS) and its potential applications to the analysis of high molecular mass compounds present in complex biological matrices from the analytical chemistry perspective. Lysozyme served as the model analyte and human saliva as the complex biological matrix in this study. A mixture of five low‐molecular mass compounds was found and successfully used in the pITP experiments as discrete spacers to isolate the analyte from the interferents present in the complex biological matrix and to minimize their disturbance effect on the final MS analysis. The experiments at the pITP stage were performed in the cationic mode. On‐column conductivity detectors were used for the detection of ITP zones. Lysozyme was found in the human saliva samples using just deconvolution of the MS data after background correction. The MS data obtained from HPLC‐MS analysis of pITP fractions exhibited the great analytical potential of the combination of pITP‐HPLC‐MS resulting from the ITP clean‐up effect as well as the ITP preconcentration of the analyte present at low concentration levels in complex biological matrices.     

Solid-phase microextraction: a powerful sample preparation tool prior to mass spectrometric analysis

Sample preparation is an essential step in analysis, greatly influencing the reliability and accuracy of resulted the time and cost of analysis. Solid-Phase Microextraction (SPME) is a very simple and efficient, solventless sample preparation method, invented by Pawliszyn in 1989. SPME has been widely used in different fields of analytical chemistry since its first applications to environmental and food analysis and is ideally suited for coupling with mass spectrometry (MS). All steps of the conventional liquid-liquid extraction (LLE) such as extraction, concentration, (derivatization) and transfer to the chromatograph are integrated into one step and one device, considerably simplifying the sample preparation procedure. It uses a fused-silica fibre that is coated on the outside with an appropriate stationary phase. The analytes in the sample are directly extracted to the fibre coating. The SPME technique can be routinely used in combination with gas chromatography, high-performance liquid chromatography and capillary electrophoresis and places no restriction on MS. SPME reduces the time necessary for sample preparation, decreases purchase and disposal costs of solvents and can improve detection limits. The SPME technique is ideally suited for MS applications, combining a simple and efficient sample preparation with versatile and sensitive detection. This review summarizes analytical characteristics and variants of the SPME technique and its applications in combination with MS.     

Novel analytical procedures for screening of drug residues in water, waste water, sediment and sludge

Traces of pharmaceuticals are continuously introduced into the aquatic environment mainly by sewage treatment plant effluents. Final data about their impact on the ecosystem are still partly missing. Progress in instrumental analytical chemistry has resulted in the availability of methods that allow a monitoring of these pollutants at ng L⁻¹ levels. In this review the state-of-the-art of residue analysis of pharmaceuticals by chromatographic and electrophoretic techniques is summarized. Improvements in detection limits over the past years have mainly been due to sophisticated mass spectrometric detection techniques. Furthermore, robust sample preparation and preconcentration protocols based on solid-phase extraction and related procedures have contributed significantly to the achievements observed so far. This review also covers several immunochemical approaches which may serve as an inexpensive alternative for quick screening of samples.     

Supramolecular complexes based on cyclodextrins

A summary of the application of cyclodextrins (CDs) in the field of supramolecular chemistry has been given. Unique structural features of CDs, namely the separation of hydrophilic and hydrophobic groups, cause unusual physical and chemical properties of these molecules. The most important property of natural or chemically modified CDs is the ability to reversibly and selectively bind organic, inorganic, and biological molecules, forming inclusion complexes (ICs) of the “guest-host” type or nanostructured supramolecular assemblies. The most interesting examples of the application of ICs with CDs in pharmaceutical, food, and chemical industry, spectrometric analysis, separation technologies, of the use of CDs as models for molecular recognition in biology, as well as the cyclical component in the construction of supramolecular architectures (rotaxanes, pseudorotaxanes) are given in the review. The mechanism and methods of the formation of ICs, their properties and the methods of analysis have been described. Particular attention has been paid to molecular necklaces. One of the new promising directions of the application of CDs, namely, the preparation of nanosized materials, has been considered.     

The fluorous effect in biomolecular applications

From being a niche area only a few decades ago, fluorous chemistry has gained momentum and is, nowadays, a fervent area of research. It has brought forth, in fact, numerous applicative innovations that stretch among different fields: from catalysis to separation science, from supramolecular to materials and analytical chemistry. Recently, the unique features of perfluorinated compounds have reached the attention of the biochemists' audience. This tutorial review introduces the basic concepts of fluorous chemistry and illustrates its main biomolecular applications. Special attention has been given to fluorous microarrays and their combination with Mass-Spectroscopy (MS) techniques, to protein properties modification by the introduction of local fluorous domains, and to the most recent applications of (19)F-Magnetic Resonance Imaging ((19)F-MRI).     

Analysis of acetamiprid in vegetables using gas chromatography-tandem mass spectrometry.

A new analytical method has been validated for determining the insecticide acetamiprid in vegetables using gas chromatography (OC) and different mass spectrometric detection techniques, such as full-scan mass spectrometry (MS), and tandem mass spectrometry (MS/MS). For this purpose, a previous extraction of the vegetable sample was carried out with ethyl acetate. In GC-MS/MS, the lowest detectable concentration was 0.001 mg kg(-1), the average recovery rates at various fortification levels (0.015 and 0.030 mg kg(-1)) ranged between 82.4 and 85.7% and the relative standard deviations were lower than 12.2% in all cases.     

Importance of weak interactions in the formulation of organic phases for efficient liquid/liquid extraction of metals

Recent experimental studies demonstrate the need to take into account weak interactions in the understanding of solvent extraction processes. This well-established industrial technology now beneficiates of a supramolecular approach, complementary to the traditional analysis based on coordination chemistry. In this article, we focus on the integration of a colloidal approach in the analysis of solvent extraction systems: organic phases used are complex fluids, in which extracting molecules self-assemble into reverse aggregates. We detail the available analytical tools used towards characterization of these organic phases and emphasize the recent results in aggregation-driven extraction. All experimental data are discussed in light of theoretical approaches which propose adequate thermodynamic models and shed light on the importance of entropy on the phenomena. Diluent effects and synergism have been successfully rationalized, efficient new formulations based on a physicochemical analysis have been proposed and the door is now open for further development at industrial scale.     

Determination of tetracycline antibiotics in cow's milk by liquid chromatography/tandem mass spectrometry

A liquid chromatographic/tandem mass spectrometric (LC/MS/MS) multiresidue method for the simultaneous quantitative determination of oxytetracycline, 4-epi-oxytetracycline, tetracycline, 4-epi-tetracycline, chlortetracycline, 4-epi-chlortetracycline and doxycycline in milk has been developed. An extraction procedure consisting of a liquid extraction of the milk samples with trichloroacetic acid was performed. The extract was centrifuged and the supernatant was filtered. Solid-phase extraction (SPE) with an OASIS HLB SPE column was used to clean up the sample extracts. The samples were analysed by LC/MS/MS. The LC separation was performed on a reversed-phase C18 column using gradient elution with a mobile phase consisting of water and a mixture of methanol/acetonitrile. The tetracycline analytes were detected with a quadrupole mass spectrometer using positive ion electrospray ionisation. The confirmatory method has acceptable detection limits and the different tetracyclines can be detected at a residue concentration between 5 and 20 microg/L. The method is validated according to the European requirements for veterinary drug residues and all determined parameters were found to conform to the criteria. The recovery values ranged from 90.4 to 101.2% with relative standard deviations (RSDs) no larger than 9.7%. The overall or between-day precision of the analytical assay determined as repeatability at several residue concentrations and expressed as RSD ranged from 3.3 to 10%. This analytical assay is a useful tool within the Belgian monitoring programme for confirmation of samples which have been positively screened for residues of tetracyclines in raw farm cow's milk.     

Supramolecular analytical chemistry

A large fraction of the field of supramolecular chemistry has focused in previous decades upon the study and use of synthetic receptors as a means of mimicking natural receptors. Recently, the demand for synthetic receptors is rapidly increasing within the analytical sciences. These classes of receptors are finding uses in simple indicator chemistry, cellular imaging, and enantiomeric excess analysis, while also being involved in various truly practical assays of bodily fluids. Moreover, one of the most promising areas for the use of synthetic receptors is in the arena of differential sensing. Although many synthetic receptors have been shown to yield exquisite selectivities, in general, this class of receptor suffers from cross-reactivities. Yet, cross-reactivity is an attribute that is crucial to the success of differential sensing schemes. Therefore, both selective and nonselective synthetic receptors are finding uses in analytical applications. Hence, a field of chemistry that herein is entitled "Supramolecular Analytical Chemistry" is emerging, and is predicted to undergo increasingly rapid growth in the near future.     

石油组分高分辨质谱分析进展与展望

石油是一种复杂体系,研究石油分子组成是分析化学领域的经典难题.近年来,傅里叶变换离子回旋共振质谱技术(Fourier transform ion cyclotron resonance mass spectrometry,FT-ICR MS)的发展,为从分子水平认识石油组成提供了机会,引起了石油化学界的高度关注,并被期待能在石油、石化领域的相关研究中实现重大突破.本文从质谱分辨率和电离技术方面介绍了石油样品的分析需求,总结了近几年基于FT-ICR MS技术对石油分子组成的研究进展,分析了其在应用中存在的关键技术问题及下一步研究方向,并对FT-ICR MS的发展前景给予展望.     

石墨烯在分析科学中的应用新进展

石墨烯因其独特的物理、化学性质在理论和应用研究上引起广泛关注,在电化学、分析化学及生命分析化学等领域具有很好的应用前景。本文简要介绍了石墨烯的制备和功能化修饰,并概述了近年来石墨烯和氧化石墨烯等材料在样品前处理、传感器、荧光分析及质谱分析等方面的应用进展。