Recent advances in analytical chemistry--a material approach

Advancements of materials research have profound direct impacts on developments in analytical chemistry and may hold the key to improvement of existing or new techniques at present times and near future. Applications of materials in analytical chemistry are reviewed, with focus on sensors, separations and extraction techniques. This review aims to survey examples of interesting works carried out in the last five years over a broad spectrum of materials classified as hybrids, nanomaterials and biomolecular materials.     

Layer double hydroxides (LDHs)- based electrochemical and optical sensing assessments for quantification and identification of heavy metals in water and environment samples: A review of status and prospects

One of the most severe environmental problems is heavy metal contamination, putting the world's sustainability at risk. Much effort has been put into developing sensors that can be taken anywhere to detect the environmental effects of heavy metals. Sensitivity, selectivity, multiplexed detection ability, and mobility enhance significantly when nanoparticles and nanostructures are incorporated into sensors. LDHs (layered double hydroxides) have gotten much attention in analytical chemistry in recent years because of their benefits, including their large specific surface area, ease of synthesis, low cost, and high catalytic efficiency and biocompatibility. LDHs are often manufactured as nanomaterial composites or created with specialized three-dimensional structures depending on the application. However, in these settings, LDHs (as color indicators, extracting sorbents, and electrochemical sensing) are usually restricted. Upcoming signs of progress and development possibilities of LDHs in analytical chemistry are reviewed in this paper to assist overcome these problems. Furthermore, the approaches used in the design of LDHs, including structural aspects, are defined and assessed in preparation for future analytical applications. The latest advances in optical and electrochemical sensors to detect heavy metals are described in this review. The sorts and characteristics of LDHs will be explored first. We will then go into microelectrode (or nanoelectrode) arrays, nanoparticle-modified electrodes, and microfluidic optical and electrochemical sensing assays in detail. This paper also discusses design strategies for LDH-based nanostructured sensors and the advantages of using nanomaterials and nanostructures.     

Recent development in nanomaterials fabricated paper-based colorimetric and fluorescent sensors: A review

The paper-based sensing devices have drawn a broad interest in analytical chemistry for colorimetric and fluorescent-based analysis of biological, environmental, clinical, and food samples. It is due to the simple, rapid, biodegradable, user-friendly, less expensive, and low waste generation into the environment. Here, the recent development of paper-based sensors fabricated with different noble metal nanoparticles (NPs) and semiconductor and carbon quantum dots (QDs) is demonstrated to analyze several chemical substances from various samples. User-friendly and portable recording devices such as digital cameras, smartphones, scanners, etc. along with color detecting softwares are employed to measure the color intensity of nanomaterials fabricated paper devices after the deposition of a sample solution containing various chemical substances. The advantages and disadvantages of incorporating nanomaterials in the paper substrate (direct deposition, inkjet printing, screen printing and wax printing) are illustrated. The mechanism for colorimetric, fluorescence, phosphorescence, and chemiluminescence sensing using noble metal NPs (Ag, Cu, and Au), semiconductors, and carbon QDs for the determination of metal ions, anions, pesticides, biomolecules, and other toxic chemical substances are discussed. Thus, this review article would be highly useful for scientists and researchers to design colorimetric sensors to monitor chemical toxicants in clinical, environment, foods, and many other related samples.     

Electrochemical Sensors,a Bright Future in the Fabrication of Portable Kits in Analytical Systems

Analysis of food, pharmaceutical, and environmental compounds is an inevitable issue to evaluate quality of the compounds used in human life. Quality of drinking water, food products, and pharmaceutical compounds is directly associated with human health. Presence of forbidden additives in food products, toxic compounds in water samples and drugs with low quality lead to important problems for human health. Therefore, attention to analytical strategy for investigation of quality of food, pharmaceutical, and environmental compounds and monitoring presence of forbidden compounds in materials used by humans has increased in recent years. Analytical methods help to identify and quantify both permissible and unauthorized compounds present in the materials used in human daily life. Among analytical methods, electrochemical methods have been shown to have more advantages compared to other analytical methods due to their portability and low cost. Most of big companies have applied this type of analytical methods because of their fast and selective analysis. Due to simple operation and high diversity of electroanalytical sensors, these types of sensors are expected to be the future generation of analytical systems. Therefore, many scientists and researchers have focused on designing and fabrication of electroanalytical sensors with good selectivity and high sensitivity for different types of compounds such as drugs, food, and environmental pollutants. In this paper, we described the mechanism and different examples of DNA, enzymatic and electro‐catalytic methods for electroanalytical determination of drug, food and environmental compounds.     

Enzymatic photometric determination of lactate by reversible reduction of methylene blue

Summary After a brief discussion of the state of development of the theory of analytical chemistry and the need for a new evaluation of its status among other fields the paper addresses one of the central subjects in classical epistemology: realism. Summarizing the development of epistemology in the last 50 years it is argued that the quest for certainty, which was one of its driving forces, cannot be fulfilled. Science and philosophy are equally entitled to contribute to the construction of a world picture. Both can only deliver hypothetical knowledge. Analytical chemistry supports an evolutionary epistemology: the multitude of sensors developed in the last fifty years can be seen as analogous to new sense organs. Seen from an evolutionary perspective analytical chemistry has tremendously enlarged the variety of sensors for actively seeking information on selected features of reality. In spite of all the difficulties in working out a realistic interpretation of quantum mechanics, the consistency of the picture of the external world delivered by the sense organs of different animals and the culturally developed sensors of analytical chemistry is a strong argument for a modest scientific realism.     

Silicon nanowires as field-effect transducers for biosensor development: A review

The unique electronic properties and miniaturized dimensions of silicon nanowires (SiNWs) are attractive for label-free, real-time and sensitive detection of biomolecules. Sensors based on SiNWs operate as field effect transistors (FETs) and can be fabricated either by top–down or bottom–up approaches. Advances in fabrication methods have allowed for the control of physicochemical and electronic properties of SiNWs, providing opportunity for interfacing of SiNW-FET probes with intracellular environments. The Debye screening length is an important consideration that determines the performance and detection limits of SiNW-FET sensors, especially at physiologically relevant conditions of ionic strength (>100 mM). In this review, we discuss the construction and application of SiNW-FET sensors for detection of ions, nucleic acids and protein markers. Advantages and disadvantages of the top–down and bottom–up approaches for synthesis of SiNWs are discussed. An overview of various methods for surface functionalization of SiNWs for immobilization of selective chemistry is provided in the context of impact on the analytical performance of SiNW-FET sensors. In addition to in vitro examples, an overview of the progress of use of SiNW-FET sensors for ex vivo studies is also presented. This review concludes with a discussion of the future prospects of SiNW-FET sensors.     

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。     

Electrochemistry in Carbon‐based Quantum Dots

Electrochemistry belongs to an important branch of chemistry that deals with the chemical changes produced by electricity and the production of electricity by chemical changes. Therefore, it can not only act a powerful tool for materials synthesis, but also offer an effective platform for sensing and catalysis. As extraordinary zero‐dimensional materials, carbon‐based quantum dots (CQDs) have been attracting tremendous attention due to their excellent properties such as good chemical stability, environmental friendliness, nontoxicity and abundant resources. Compared with the traditional methods for the preparation of CQDs, electrochemical (EC) methods offer advantages of simple instrumentation, mild reaction conditions, low cost and mass production. In return, CQDs could provide cost‐effective, environmentally friendly, biocompatible, stable and easily‐functionalizable probes, modifiers and catalysts for EC sensing. However, no specific review has been presented to systematically summarize both aspects until now. In this review, the EC preparation methods of CQDs are critically discussed focusing on CQDs. We further emphasize the applications of CQDs in EC sensors, electrocatalysis, biofuel cells and EC flexible devices. This review will further the experimental and theoretical understanding of the challenges and future prospective in this field, open new directions on exploring new advanced CQDs in EC to meet the high demands in diverse applications.     

A review of opportunities for electrospun nanofibers in analytical chemistry

Challenges associated with analyte and matrix complexities and the ever increasing pressure from all sectors of industry for alternative analytical devices, have necessitated the development and application of new materials in analytical chemistry. To date, nanomaterials have emerged as having excellent properties for analytical chemistry applications mainly due to their large surface area to volume ratio and the availability of a wide variety of chemical and morphological modification methods. Of the available nanofibrous material fabrication methods, electrospinning has emerged as the most versatile. It is the aim of this contribution to highlight some of the recent developments that harness the great potential shown by electrospun nanofibers for application in analytical chemistry. The review discusses the use of electrospun nanofibers as a platform for low resolution separation or as a chromatographic sorbent bed for high resolution separation. It concludes by discussing the applications of electrospun nanofibers in detection systems with a specific focus on the development of simple electrospun nanofiber based colorimetric probes.     

辣根过氧化物酶在分析化学中的应用

辣根过氧化物酶是一种重要的分析化学试剂,对过氧化氢底物特异性强。广泛用于临床化学、环境化学和食品工业等领域。本文评述了近十年来辣根过氧化物酶在分析化学中的应用进展。包括光度法、荧光法、化学发光法、电化学传感器和光导纤维传感器法测定过氛氢及相关物质,及辣根过氧化物酶在其他无机、有机及生物物质分析中的应用。引用参考文献６０篇。     

Electrochemistry in solids prepared by sol-gel processes

Sol-gel chemistry provides a route to preparing inorganic polymers with ionically conducting properties by room temperature synthetic routes. The products, which are rigid solids, are well-suited as media for conventional electrochemical techniques such as cyclic voltammetry. This property, when combined with their ability to host a wide variety of species, has allowed development of a variety of devices of interest in electrochemistry and analytical chemistry. Examples include cathodes for fuels cells, electrochromic devices, biosensors, and amperometric sensors for analytes in the gas phase. In this review, the emphasis will be on reported applications to analytical chemistry; however, studies on the general properties of these materials and on their use in electrochemical science also will be summarized because they may provide the basis for further development of sensors.     

Amide- and urea-functionalized pyrroles and benzopyrroles as synthetic, neutral anion receptors

This critical review is dedicated to the anion complexation chemistry of amide- and urea-functionalized (benzo)pyrroles, such as pyrroles, indoles, carbazoles, isoindoles, naphthalenodipyrroles and benzodipyrroles. It provides a comprehensive overview of these simple and neutral anion sensors from the first examples up to very recent studies. There is a discussion of a gradual progress made over time, often based on careful analysis of the properties of former generations that have subsequently led to obtaining excellent effectivities and selectivities. The influence of these species on other fields of chemistry and their applications there are also discussed (57 references).     

Template-directed porous electrodes in electroanalysis

Nano- and/or macrostructuring of electrode surfaces has recently emerged as a powerful method of improving the performances of electrochemical devices by enhancing both molecular accessibility and rapid mass transport via diffusion, by increasing the electroactive surface area in comparison to the geometric one, and/or by providing confinement platforms for hosting suitable reagents. This brief overview highlights how template technology offers advantages in terms of designing new types of porous electrodes—mostly based on thin films, and functionalized or not—and discusses their use in analytical chemistry via some recent examples from the literature on electrochemical sensors and biosensors.      

Immunoassays in environmental analytical chemistry

A review is presented which summarizes the recent developments of immunoassays in environmental analytical chemistry. The basic principle of the method and the following steps in the development of an immunoassay procedure are discussed in detail: Synthesis of the immunogen, immunization procedure, synthesis of the labelled antigen (tracer), advantages and drawbacks of radioimmunoassay, fluoroimmunoassay and enzyme immunoassay. A special emphasis is put on approved methods which can be applied in almost any analytical laboratory. Numerous examples of immunoassays for different pesticides and pollutants (dioxins, polychlorinated biphenyls, mycotoxins) are presented. Besides the respective test features, their applicability for residue determinations in biological samples is kept in the foreground. The advantages and drawbacks of the immunoassays are discussed in comparison with conventional analytical methods. An outlook to future application fields for immunoassays and new trends (e.g. the utilization of monoclonal antibodies) is presented.     

Optimization by statistical linear discriminant analysis in analytical chemistry

The application of statistical linear discriminant analysis in analytical chemistry is discussed. In addition to a general discussion of the theory of the method, which is illustrated by some examples, its suitability for problem solving in analytical chemistry is demonstrated by a review of published applications. A more mathematical point of view is added as an appendix.     

Present and future applications of carbon nanotubes to analytical science

This article reviews the impact of carbon nanotubes on analytical science, and the main current and future applications of carbon nanotubes in this field. Given that it is necessary to solubilize carbon nanotubes for many applications, we consider the procedures developed to achieve this. The use of carbon nanotubes in analytical chemistry as a target analyte and as an analytical tool is also discussed. Chromatographic and electrophoretic methods used to separate and characterize carbon nanotubes are presented. The use of carbon nanotubes as an analytical tool in filters and membranes, as sorbent material for solid phase extraction, in electrochemical (bio)sensors, and in separation methods is discussed. It is clear that while nanotubes are being tested for use in many different fields, their truly enormous potential has yet to be realized in analytical chemistry.Dedicated to the memory of Wilhelm Fresenius     

QM/MM: what have we learned,where are we,and where do we go from here?

This paper briefly reviews the current status of the most popular methods for combined quantum mechanical/molecular mechanical (QM/MM) calculations, including their advantages and disadvantages. There is a special emphasis on very general link-atom methods and various ways to treat the charge near the boundary. Mechanical and electric embedding are contrasted. We consider methods applicable to gas-phase organic chemistry, liquid-phase organic and organometallic chemistry, biochemistry, and solid-state chemistry. Then we review some recent tests of QM/MM methods and summarize what we learn about QM/MM from these studies. We also discuss some available software. Finally, we present a few comments about future directions of research in this exciting area, where we focus on more intimate blends of QM with MM. Contribution to the Proceedings of the 10th Electronic Computational Chemistry Conference     

Searching for signals in the noise: metabolomics in chemical ecology

Chemically mediated interactions between organisms influence ecosystem structure, making it crucial for ecologists to understand these interactions. Advances in chemical ecology have often been closely linked to advances in analytical chemistry techniques. One recent development is the use of metabolomics to address questions in chemical ecology. Although metabolomics has much to offer this field, it is not without drawbacks. Here we consider how metabolomics techniques can supplement the traditional bioassay-guided fractionation approach to chemical ecology. We focus on specific examples that illustrate the advantages that metabolomic methods can provide over other methods in order to understand chemically mediated interactions between organisms.     

The Kalman filter in analytical chemistry

During the past ten years, the means by which more information can be extracted from experimental data have become an important area of research in analytical chemistry. Digital filters have been demonstrated to have a number of applications to analytical problems. These techniques typically involve a least-squares fit of experimental data to some model of the process being filtered. One method for filtering experimental data is based on the Kalman filter, a recursive, linear digital filter first developed for use in navigation, but now used in many fields. This paper discusses the implementation of Kalman filters in analytical chemistry. The principles of state-space digital filtering are reviewed, and the development of state/space models is discussed. Discussion is focused on the discrete Kalman algorithms. Two examples are provided to demonstrate the operation of the discrete Kalman filtering algorithm. Similarities between Kalman filtering and weighted least-squares methods are considered, and the specific advantages and disadvantages of linear and nonlinear Kalman filtering approaches are evaluated. To illustrate the range of problems which benefit from use of the filter, a comprehensive literature survey of the application of Kalman filtering to chemical problems is provided.     

A general approach for rational design of fluorescent DNA aptazyme sensors based on target-induced unfolding of DNA hairpins

DNA aptazymes are allosteric DNAzymes activated by the targets of DNA aptamers. They take the advantages of both aptamers and DNAzymes, which can recognize specific targets with high selectivity and catalyze multiple-turnover reactions for signal amplification, respectively, and have shown their great promise in many analytical applications. So far, however, the available examples of DNA aptazyme sensors are still limited in utilizing only several DNAzymes and DNA aptamers, most likely due to the lack of a general and simple approach for rational design. Herein, we have developed such a general approach for designing fluorescent DNA aptazyme sensors. In this approach, aptamers and DNAzymes are connected at the ends to avoid any change in their original sequences, therefore enabling the general use of different aptamers and DNAzymes in the design. Upon activation of the aptazymes by the targets of interest, the rate of fluorescence enhancement via the cleavage of a dually labeled substrate by the active aptazymes is then monitored for target quantification. Two DNAzymes and two aptamers are used as examples for the design of three fluorescent aptazyme sensors, and they all show high selectivity and sensitivity for the detection of their targets. More DNA aptazyme sensors for a broader range of targets could be developed by this general approach as long as suitable DNAzymes and aptamers are used.