Applications In Analytical Chemistry Research Articles

A particle-based microfluidic molecular separation integrating surface-enhanced Raman scattering sensing for purine derivatives analysis

Based on its highly specific and non-invasive features, surface-enhanced Raman scattering (SERS) has been applied for analytical chemistry or biological applications, such as identification of chemical compositions, cells or bacteria. However, if the targeted sample consists of multiple compounds, the corresponded SERS spectra would be quite difficult to analyze. To address above problems, we developed a particle-based microfluidic molecular separation (PMMS) integrating SERS substrate to separate complicate molecule mixture followed by in situ SERS detection. The platform consists of an automatic microfluidic control system to precisely control the sample and reagent flow in the PMMS–SERS device, composed of a 5-µm particle-packed separation column followed by a two-dimensional Ag nanostructural substrate. To proof-of-concept, we first tested the molecule separation functionality using the mixture of fluorescent FITC and R6G dyes. Later, we introduced the hypoxanthine and adenine mixture—main purine metabolites of E. coli—into the system for on-chip separation, identification, and quantification based on acquired SERS signatures. Overall, the miniaturized PMMS–SERS system enables an easy-to-use and sensitive analyte detection, which could be beneficial in applications requiring bacteria identification and quantification, such as environmental monitoring, AST, and drug development.

Recent Advances in 2D Inorganic Nanomaterials for SERS Sensing.

Surface-enhanced Raman spectroscopy is a powerful and sensitive analytical tool that has found application in chemical and biomolecule analysis and environmental monitoring. Since its discovery in the early 1970s, a variety of materials ranging from noble metals to nanostructured materials have been employed as surface enhanced Raman scattering (SERS) substrates. In recent years, 2D inorganic materials have found wide use in the development of SERS-based chemical sensors owing to their unique thickness dependent physico-chemical properties with enhanced chemical-based charge-transfer processes. Here, recent advances in the application of various 2D inorganic nanomaterials, including graphene, boron nitride, semiconducting metal oxides, and transition metal chalcogenides, in chemical detection via SERS are presented. The background of the SERS concept, including its basic theory and sensing mechanism, along with the salient features of different nanomaterials used as substrates in SERS, extending from monometallic nanoparticles to nanometal oxides, is comprehensively discussed. The importance of 2D inorganic nanomaterials in SERS enhancement, along with their application toward chemical detection, is explained in detail with suitable examples and illustrations. In conclusion, some guidelines are presented for the development of this promising field in the future.

A facile and robust SERS platform for highly sensitive and reproducible detection of uracil-DNA glycosylase using target-activated plasmonic coupling

The self-assembly plasmonic nanoparticles with effective coupling have drawn considerable interest in quantitative surface-enhanced Raman scattering (SERS) detection, which facilitate their practical applications in chemical and biomolecular analysis. Herein, we report the development of a robust, sensitive and reproducible SERS platform for Uracil-DNA glycosylase (UDG) quantification using target-activated plasmonic coupling. This system consists of DNA substrates and Raman dyes-decorated gold nanoparticles (AuNPs) that functions as a target-recognition and SERS signal-output tool, and two kinds of enzymes, exonuclease I (Exo I) and endonuclease IV (Endo IV) that are utilized to degrade DNA substrates on AuNPs for controllable self-assembly of plasmonic nanoparticles. On account of this skilled design of SERS system, self-assembled hot spots with uniform interparticle gap and narrow enhancement factors (EFs) can be readily and repeatedly constructed by target-activated dual enzymatic cleavage reaction, which allows highly sensitive and reproducible SERS sensing of target UDG. Under optimized experimental conditions, the proposed biosensor exhibits excellent analytical performance toward the detection of UDG with a detection limit of 4.29 × 10−4 U mL−1 within a linear range of 1.0 × 10−3 U mL−1 to 10 U mL−1 for UDG, along with a favorable specificity and reproducibility. In addition, the practical applicability of this biosensor is demonstrated by the detection of UDG in cell extracts with satisfactory results. Hence, the target-activated plasmonic coupling-based strategy indeed creates a robust and convenient platform for UDG identification and related biomedicine research and clinical diagnosis.

Application of electro analytical chemistry for the corrosion process on the stainless steel electrodes in the acidic thiourea

A cyclic voltammetry study is one of electro analytical chemistry methods which able to study the corrosion of material. In this research, the cyclic voltammetry has been carried out in order to determine the voltage range that contributes to the initiation of the corrosion on the surface of stainless steel in the acidic thiourea solution. In this study, the knowledge of corrosion on stainless steel is useful in the optimisation process for gold recovery from electronic waste based on electrodeposition technique. Since stainless steel material has been used as both anode and cathode in the experimental setup, under certain applied voltage, corrosion might occur and hinder the gold recovery process by damaging the electrodes. With the aid of cyclic voltammetry study, the suitable applied voltage for electrodeposition process has been investigated and found to be approximately 1.4 V for two-electrode setup for a system with sulfuric acid concentration of 0.1 M in the presence of 0.1 M thiourea. The data obtained can be used as a basis to determine a suitable pre-set applied voltage in the electrodeposition process such that corrosion on the electrodes can be avoided.

The Application of NIR Process Analytical Chemistry in Studying Competitive Adsorption Process

With an experimental setup of near-infrared process analytical chemistry, a competitive adsorption process of orthoxylene and aniline vapor onto silica gel has been revealed in the paper. The mixture vapor of orthoxylene and aniline has been introduced into a quartz adsorption bed, which was filled with adsorbent of silica gel and monitored continuously by a near-infrared spectrometer. Based on near-infrared spectra recorded during the adsorption process and chemometrics methodologies, the competitive adsorption process has been studied completely as well as clearly: 1) at about 62 minutes the adsorption achieved its equilibrium or stable state with aniline concentration of 0.22 g/g, and without any orthoxylene; 2) othoxylene was adsorbed first, but then rapidly replaced by aniline; 3) the adsorption of aniline resulted from the hydrogen bonds between aniline’s amino groups and silica gel’s silanol groups while that of orthoxylene was due to physical adsorption; 4) aniline was adsorbed vertically on the silica gel but orthoxylene laid evenly; 5) some surface of silica gel was more active for adsorption than others.

Use of Natural Deep Eutectic Solvents for Polymerization and Polymer Reactions

Green chemistry is a key opportunity in chemistry and chemical engineering today because it can potentially preserve the environment and human health. It entails the choice of natural biodegradable raw materials and solvents, environmentally acceptable processes, and minimal use of non-hazardous chemicals. Previously, deep eutectic solvents (DES) have found many applications in organic, analytical, and polymer chemistry. The recent discovery of natural deep eutectic solvents (NADES), where many plant-abundant primary metabolites have been found to change their state from solid to liquid at certain temperatures when mixed in a proper ratio, should accelerate their use as replacements for common organic solvents that exhibit inherent toxicity and high volatility. In this work, we have reviewed the application of NADES as green, sustainable solvents in processes that involve polymerizations and polymer reactions. It is clear that many applications have already been explored. Undoubtedly more progress will be made in the future, and NADES will become more commonly used in polymer-related processes.

Recent advances in hyphenation of nanoflow liquid phase separation with inductively coupled plasma mass spectrometry

High-performance nanoflow liquid-phase separation techniques such as nanoflow liquid chromatography (nanoLC), capillary electrophoresis (CE), and microchip chromatography and electrophoresis (chip-ICP-MS) have been hyphenated with inductively coupled plasma mass spectrometry (ICP-MS) extensively. This hyphenation combines the excellent characteristics of the front-end separation technology, such as high selectivity, sensitivity, and speed, and low sample consumption, and the advantages of back-end ICP-MS, such as high resolution, wide dynamic range, and absolute quantification capability. Thus, such hyphenation is becoming an increasingly important analytical tool. Herein we systematically introduce the recent development of hyphenated nanoLC, CE, and chip-ICP-MS, review its application in chemical and biochemical analysis, and discuss potential future developments of hyphenating these technologies.

Microfabricated needle for hydrogen peroxide detection.

A microfabricated needle-like probe has been designed and applied for hydrogen peroxide (H2O2) sampling and detection using a commercial, single-step fluorescent H2O2 assay. In this work, droplets of the assay reagent are generated and sent to the needle tip using a mineral-oil carrier fluid. At the needle tip, the sample is drawn into the device through 100 μm long hydrophilic capillaries by negative pressure. The sampled fluid is immediately merged with the assay droplet and carried away to mix and react, producing a sequence of droplets representing the H2O2 concentration as a function of time. We have characterized the assay fluorescence for small variations in the sample volume. With the calibration, we can calculate the concentration of H2O2 in the sampled liquid from the size and intensity of each merged droplet. This is a microfluidic data-logger system for on-site continuous sampling, controlled reaction, signal storage and on-line quantitative detection. It is a useful tool for monitoring dynamic chemical reactions in analytical chemistry and biological applications.

Digestion of Dynamic Substrate by Exonuclease Reveals High Single-Mismatch Selectivity.

The distinctive nuclease activity toward nucleic acid substrates enables various applications in analytical chemistry and dynamic DNA nanotechnology. λ Exonuclease is a widely used tool for the processing of PCR products, and DNA sequencing. This enzyme also shows promise for reducing the leakage (i.e., activation in absence of a correct input) in DNA-based analytical methods and nanotechnology due to its sensitivity to mismatches. However, the selectivity of λ exonuclease for single-mismatch in most applications is not high. Inspired by the increased specificity of dynamic probes in DNA nanotechnology, we enhanced the single-mismatch selectivity of λ exonuclease by using very short double-stranded DNA (dsDNA) as the substrate. From the bulk fluorescence measurements, short perfectly matched (PM) substrate which is as a correct input can be effectively digested, but the existence of single-mismatch drastically reduces the digestion rate. Real-time single-molecule kinetics analysis reveals that PM substrate can be selectively stabilized by the binding of λ exonuclease, which combines with the differential stability of transient hybridization of short substrates to yield high single-mismatch selectivity. An excellent selective assay for a single-nucleotide mutation in KRAS was demonstrated, which permits detecting this mutation from cell line at as low as 0.02%, holding potential for detecting rare mutations in circulating tumor DNA of early stage cancers.

Application Research on Information Teaching in the Process of Analytical Chemistry Education

With the continuous development of society, human beings are in the midst of profound changes. The new information thinking has penetrated into society, study, work and life. The application of information technology has become an important direction for the teaching reform of chemistry. By analyzing the application status of information education and teaching, this paper concludes that the construction of information teaching resources needs to be improved, and the application of information teaching technology still needs to be strengthened, and proposes the idea of integrating it with innovation and development, using information technology. Improve the teaching concepts of chemistry subjects, improve teaching resources and improve the application of information technology. Due to the introduction of information technology, it can highlight the characteristics of rapid, sensitive and accurate analysis of chemistry. The combination of various teaching methods makes the application of analytical chemistry more extensive and strongly promotes the development of analytical chemistry. Change traditional teaching methods and traditional education models, and innovate teaching concepts and practical concepts. It is believed that the continuous integration of information technology in development and rapid social economy will definitely create an information environment for the whole society

Porous Organic Frameworks: Advanced Materials in Analytical Chemistry.

Porous organic frameworks (POFs), a general term for covalent‐organic frameworks (COFs), covalent triazine frameworks (CTFs), porous aromatic frameworks (PAFs), etc., are constructed from organic building monomers with strong covalent bonds and have generated great interest among researchers. The remarkable features, such as large surface areas, permanent porosity, high thermal and chemical stability, and convenient functionalization, promote the great potential of POFs in diverse applications. A critical overview of the important development in the design and synthesis of COFs, CTFs, and PAFs is provided and their state‐of‐the‐art applications in analytical chemistry are discussed. POFs and their functional composites have been explored as advanced materials in “turn‐off” or “turn‐on” fluorescence detection and novel stationary phases for chromatographic separation, as well as a promising adsorbent for sample preparation methods. In addition, the prospects for the synthesis and utilization of POFs in analytical chemistry are also presented. These prospects can offer an outlook and reference for further study of the applications of POFs.

Design and Simulation of Microfluidic Device for Metabolite Screening and Quantitative Monitoring of Drug Uptake in Cancer Cells.

Although liquid-liquid extraction methods are currently being applied in many areas such as analytical chemistry, biochemical engineering, biochemistry, and biological applications, accessibility and usability of microfluidics in practical daily life fields are still bounded. Suspended microfluidic devices have the potential to lessen the obstacles, but the absence of robust design rules have hampered their usage. The primary objective of this work is to design and fabricate a microfluidic device to quantitatively monitor the drug uptake of cancer cells. Liquid-liquid extraction is used to quantify the drug uptake. In this research work, designs and simulations of two different microfluidic devices for carrying out multiplex solution experiments are proposed to test their efficiency. These simplified miniaturized chips would serve as suspended microfluidic metabolites extraction platform as it allows extracting the metabolites produced from the cancer cells as a result of applying a specific drug type for a certain period of time. These devices would be fabricated by making polydimethylsiloxane (PDMS) molds from the negative master mold using soft lithography. Furthermore, it can leverage to provide versatile functionalities like high throughput screening, cancer cell invasions, protein purification, and small molecules extractions. As per previous studies, PDMS has been depicting better stability with various solvents and has proved to be a reliable and cost effective material to be used for fabrication, though the sensitivity of the chip would be analyzed by cross contamination and of solvents within the channels of device.

Three-dimensional printed microfluidic modules for design changeable coaxial microfluidic devices

Coaxial microfluidic devices have been widely used for the preparation of monodisperse droplets and multi-layered hydrogel fibers. However, in the formation of the coaxial microfluidic devices, as the configurations of the coaxial channels become larger and more complicated, the production time is prolonged, the yield is reduced, and there are difficulties associated with rinsing the channels. In this paper, we propose three-dimensional (3D) printed microfluidic modules as connectable platforms for the preparation of coaxial microfluidic devices. Since the microfluidic modules have simple channel configurations, we can easily fabricate them with a 3D printer and rinse their channels after use. The combination of the microfluidic modules allows the formation of various types of coaxial microfluidic devices, such as axisymmetric flow-focusing devices and co-flow devices with specified dimensions for their channels. Therefore, devices comprising these microfluidic modules have succeeded in production of monodisperse droplets and hydrogel fibers with various dimensions and different numbers of layers. Furthermore, as a demonstration of biofabrication applications, we show that the device comprising the microfluidic modules enables us to fabricate a multi-layered cell-laden fiber by gelation of cell-laden collagen solutions in a multi-layered laminar flow state. We believe that the microfluidic modules will be useful for preparing coaxial microfluidic devices for various applications in analytical chemistry, biology, and tissue engineering.

Key aspects of surface plasmon resonance spectroscopy for analytical chemistry applications

Key aspects of surface plasmon resonance spectroscopy for analytical chemistry applications

Wiodzimierz Kutner and Piyush Sindhu Sharma (Eds): Molecularly Imprinted Polymers for Analytical Chemistry Applications

Wiodzimierz Kutner and Piyush Sindhu Sharma (Eds): Molecularly Imprinted Polymers for Analytical Chemistry Applications

NMR Measurements Reveal the Structural Basis of Transthyretin Destabilization by Pathogenic Mutations.

Inherited mutations of transthyretin (TTR) destabilize its structure, leading to aggregation and familial amyloid disease. Although numerous crystal structures of wild-type (WT) and mutant TTRs have been determined, they have failed to yield a comprehensive structural explanation for destabilization by pathogenic mutations. To identify structural and dynamic variations that are not readily observed in the crystal structures, we used NMR to study WT TTR and three kinetically and/or thermodynamically destabilized pathogenic variants (V30M, L55P, and V122I). Sequence-corrected chemical shifts reveal important structural differences between WT and mutant TTR. The L55P mutation linked to aggressive early onset cardiomyopathy and polyneuropathy induces substantial structural perturbations in both the DAGH and CBEF β-sheets, whereas the V30M polyneuropathy-linked substitution perturbs primarily the CBEF sheet. In both variants, the structural perturbations propagate across the entire width of the β-sheets from the site of mutation. Structural changes caused by the V122I cardiomyopathy-associated mutation are restricted to the immediate vicinity of the mutation site, directly perturbing the subunit interfaces. NMR relaxation dispersion measurements show that WT TTR and the three pathogenic variants undergo millisecond time scale conformational fluctuations to populate a common excited state with an altered structure in the subunit interfaces. The excited state is most highly populated in L55P. The combined application of chemical shift analysis and relaxation dispersion to these pathogenic variants reveals differences in ground state structure and in the population of a transient excited state that potentially facilitates tetramer dissociation, providing new insights into the molecular mechanism by which mutations promote TTR amyloidosis.

Nanoporous Ag-Au Bimetallic Triangular Nanoprisms Synthesized by Galvanic Replacement for Plasmonic Applications

Galvanic replacement is a versatile method of converting simple noble metallic nanoparticles into structurally more complex porous multimetallic nanostructures. In this work, roughened nanoporous Ag-Au bimetallic triangular nanoprisms (TNPs) are synthesized by galvanic replacement between smooth Ag triangular plates and AuCl4− ions. Transmission electron microscope and the elementary mapping measurements show that numerous protrusions and pores are formed on the {111} facets, and Ag and Au atoms are homogeneously distributed on the triangular plates. Due to the additional “hot spots” generated by the surface plasmon coupling of the newly formed protrusions and pores, the roughened nanoporous Ag-Au TNP aggregates demonstrate a higher surface-enhanced Raman scattering enhancement factor (seven times larger) and better reproducibility than that of smooth Ag triangular particle aggregates. These synthesized roughened nanoporous Ag-Au bimetallic TNPs are a promising candidate for the applications in analytical chemistry, biological diagnostics, and photothermal therapy due to their excellent plasmonic performances and good biocompatibility.

Research Methods for Structural Analysis of Lactic Acid Bacteria Induced Exopolysaccharides

Abstract Exopolysaccharides (EPSs), produced by lactic acid bacteria (LAB), have been used primarily to improve the quality and taste of food, also possess a variety of unique biological functions, such as immunoregulation and anti-tumor activities. The diversity of molecular structural characteristics of LAB-generated EPSs represents one of the main factors responsible for this plethora of functions. Accordingly, the structural analysis of the EPSs produced by LAB is the prerequisite and basis for examining its functional and structure-activity relationships. In this report, we summarized the current progress of key methodologies involved in the structural analysis of LAB-generated EPSs, including their isolation, purification, primary structure and advances in structural research. A comprehensive discussion regarding the application of chemical analysis, instrument analysis and computer aided technology in the structure analysis of LAB-generated EPSs was provided. Further, the future development of the research on the structure of LAB-generated EPSs was also presented.

Infrared spectroscopy of cold trapped molecular ions using He‐tagging

This review summarizes experimental activities to study the structure of molecular ions via He tagging. The method is based on the attachment of a weakly bound helium atom to a cold ion followed by laser‐induced predissociation (LIP). Since my early involvements (it started in 1977 with a letter from Y.T. Lee), radio frequency (rf) ion traps and ion guides have been important elements in instruments dedicated to ion spectroscopy. Accumulating ions in a ring electrode trap (RET) and confining them together with the laser‐induced photofragments in a long octopole has been demonstrated in 1978 in Berkeley via photodissociation of metastable O2+ ions. In the early stage of this instrument, as well as in various further developments, supersonic expansions have been used to create weakly bound complexes. An important step forward for ion spectroscopy was to push the conditions of cryogenic ion traps so far that, finally, He atoms could be attached to almost any mass‐selected ion of interest, including multiply charged ions and C60+. Currently, modern ion storage instruments reach temperatures below 3 K and can be operated at helium densities above 1016 cm−3, opening up many avenues of application in spectroscopy, reaction dynamics, and analytical chemistry. In addition to a personal historical review, I discuss recent progress made with new cryogenic ion traps, especially in the field of He tagging. He‐M+ ions have been formed via ternary association for all kind of M+ ions ranging from atoms such as He+, N+, or Fe+ via molecules N2+, VO+, and H3+ to various polyatomic ions. The in situ synthesis of tagged ions made unique discoveries possible, such as determining the structure of doubly charged benzene, the first identification of a carrier of diffuse interstellar bands, or the characterization of the fundamental 4 electron 4 center system He–H3+. In the conclusions, hints to additional applications will be given, emphasizing on the versatility of temperature‐variable ion traps.

Operation of pneumatically-actuated membrane-based microdevices for in situ analysis of extraterrestrial organic molecules after prolonged storage and in multiple orientations with respect to Earth’s gravitational field

Pneumatically-actuated monolithic membrane microvalves are powerful microfluidic tools that can be integrated into programmable microfluidic architectures (PMAs) for multiple portable chemical analysis applications, including point-of-care (POC) diagnostics, environmental science, space exploration, etc…. However, these systems have not seen wide-scale deployment in industry or spaceflight due in part to (1) a concern that these systems may have a limited shelf-life and (2) a concern that performance depends on specific device orientation in a gravitational field. To address these concerns, we functionally tested a Mars Organic Analyzer microdevice fabricated in 2005 after 10 years of storage under ambient conditions. Using a square wave with a 500 millisecond (ms) actuation pulse width and a 1000 ms period and operating under vacuum at −980 millibar (mbar) from ambient pressure, all pneumatically-actuated valves opened in less than 1 h. The vacuum required to actuate an open valve ranged from −218 to −175 mbar from ambient pressure. The microvalves were then programmed to transfer fluid through the microdevice for flow rate characterization. Fluidic transfer occurred at a flow rate of 122 ± 8 microliters/minute (μL/min) right-side up in Earth’s gravitational field and 114 ± 14 μL/min upside down in Earth’s gravitational field, indicating likely successful implementation in an orbital microgravity environment. This demonstration that microdevices retain full functionality after over 10 years of storage combined with successful operation in multiple orientations in Earth’s gravitational field further validates the value of microdevices based on these microvalves for fluidic manipulation and sample handling in outer planetary missions.