Applications In Analytical Chemistry Research Articles

Discovery and application of food catalysts to promote the coupling of PQQ (quinone) with amines.

Biocatalysts (enzymes) play a crucial role in catalyzing specific reactions across various industries, often offering environmentally friendly and sustainable alternatives to chemical catalysts. However, their catalytic activities are susceptible to denaturation. In this study, we present the discovery of novel protein-based biocatalysts derived from processed foods, including skimmed milk, soy milk, cheese, and dried tofu. These food catalysts exhibit high availability, low cost, safety, and thermo-stability. Focusing on the physiologically intriguing coenzyme pyrroloquinoline quinone (PQQ), we observed that the reaction with glycine to form imidazolopyrroquinoline (IPQ) did not proceed efficiently when PQQ was present at very low concentrations. Surprisingly, in the presence of protein-based foods, this reaction was significantly accelerated. Notably, skimmed milk enhanced the PQQ detection limit (600 times lower) during high-performance liquid chromatography (HPLC) following IPQ derivatization. Milk appears to facilitate the reaction between PQQ and various amino acids, primary amines, and secondary amines. Further investigations revealed that food catalysis operates through a non-enzymatic mechanism. Additionally, nuclear magnetic resonance spectroscopy demonstrated that milk components interacted with amino substrates due to the ability of amines to react with quinones on colloidal surfaces. These practical food catalysts not only contribute to environmental safety but also hold significance across diverse scientific domains. Non-enzymatic protein catalysts find applications in biocatalysis, organic synthesis, food technology, analytical chemistry, and fundamental nutritional and evolutionary studies.

Hybrid photo paper-based microfluidic device for colorimetric detection of iodine in salt

Microfluidic paper-based analytical devices (µPADs) have gained widespread use in various analytical applications because they are low-cost and suitable for onsite testing. The development of µPADs, including fabrication methods, new materials, and enhancement functionality is crucial to advance their practical application in analytical chemistry. In this study, we introduce a new hybrid paper-based analytical device, the hybrid photo paper-based microfluidic device (hPPMD), which combines a photo paper-based microfluidic device (PPMD) with a µPAD. We conducted a systematic study that detailed hPPMD’s characteristics, including surface properties and fluidic transportation. The hPPMD showed two fluidic transportation behaviors: continuous flow and discontinuous flow at the device junction, depending on the orientation of the device combination. Our hPPMD could increase fluidic flow approximately four times the speed when six layers of guided channels were added. The customized hPPMD was used for colorimetric detection of iodine in table salt, and then the result was quantitatively analyzed using a computer and smartphone with color analysis software. The detection zones of the hPPMD showed a flawless circular color signal. Under optimum conditions, the hPPMD was sensitive enough to detect iodine in salt solutions at various concentrations ranging from 1 to 100 ppm. The developed hPPMD should be a simple and low-cost analytical device for onsite qualitative analysis of the iodine and other chemical contaminants in food and the environment.

Synthesis and dual sensing of vanadium and copper ions using protein capped selenium nanoparticles

Highly homogenous and spherical shaped Selenium nanoparticles with an average size of 20 nm were synthesized from an eco-friendly and environmentally safe approach using bovine milk protein casein as stabilizing agent (named as CasSeNPs). Protein functionalization provided excellent stability at variable temperatures (25–60 °C), pH (8–10), ionic strength (0.05–2 M), and storage period for more than five months. Synthesized CasSeNPs were extensively characterized using various spectroscopic (UV–visible, Fourier transform infrared (FTIR), circular dichroism (CD), intrinsic fluorescence spectroscopy), particle sizing (dynamic light scattering (DLS) and zeta potential), microscopic (scanning electron microscopy, energy dispersive X-ray spectroscopy (SEM/EDS), atomic force microscopy (AFM)), and X-ray diffraction (XRD) measurements. Moreover, CasSeNPs was established as highly sensitive and selective sensor for the simultaneous detection of vanadium (V+2) and copper (Cu+2) ions with significant linearity (0.5–10 and 0.1–1.0 µM, respectively), detection limits (LOD = 0.03 and 0.067 µM, respectively), and percent recoveries (94–105 %) in real environmental (tap water) and biological (human plasma and urine) samples with adequate test performance. Cumulatively, obtained results revealed that the established very simple, biocompatible and economical nanosensor has great potential for applications in analytical chemistry as well as for biological investigations.

Effect of fluid properties on intensification of heat transfer process in oil-water droplet flow in a T-shaped microchannel

Droplet-based microfluidics refers to the production and utilization of micrometer-sized droplets. This technology has found widespread applications in drug delivery, biotechnology, disease prevention, chemical analysis, cell research, and functional material synthesis. Cooling of high heat flux electronic systems and hot spots is another application of the droplet flow which is focused by the current work. In this paper, formation and hydrothermal performance of oil droplets in water flow in a T-junction microchannel is studied by a 3D numerical simulation. Effects of different parameters such as surface tension, wettability and heat flux on the droplet size, heat transfer rate and pressure drop are investigated. It is observed that the shear between the discrete and continuous phases results in recirculating zones in both phases which contribute to improved mixing and heat transfer rates. Liquid film thickness adjacent to the heated surface and the droplet velocity are two other factors that positively affect the heat transfer. Decreasing the surface tension is shown to enhance the heat transfer rate. Moreover, an optimum value is found for the contact angle as 135° at which a 23 % heat transfer enhancement is achieved. Results also indicate that droplet size decreases with increase of contact angle while it slightly increases with increase of the surface tension and negligibly varies with the applied heat flux.

Inductance coil high-frequency contactless chemical sensor: Systematic study of its cationic sensitivity

Contactless sensors for chemical analysis, based on inexpensive and widely available electronic components, are a promising alternative to existing routine laboratory methods. We have proposed a novel type of a contactless sensor, composed of three simple components: an alternate current generator, an inductance coil, and a receiver. The sample, placed into the coil as a core of the inductor, modifies the current passing through the coil. Previously, we have demonstrated that this contactless sensor may have numerous applications for chemical analysis. In this work, we have explored the performance of the coil-based measuring platform further and performed the first systematic study of the response of inductance coil sensor to metal cations in aqueous solutions. Sixteen metal cations with different charge and radii were studied. Linear response ranges, sensitivity values and the comparison between univariate and multivariate regression modeling are presented. The largest linear response range was observed for transition metal cations Ni2+, Cu2+, Pb2+ and Nd3+ (10-3 – 10-1 M), the narrowest – for Li+ and Gd3+ (10-2 – 3.2x10-1 M) with R2 values larger than 0.94. The dependence of the response on the radius and the charge of the cation are discussed. The analytical characteristics of the device show its potential in contactless and low-cost chemical analysis and set the ground for the future research.

Synthesis of long straight‐chain alkane substituted ferrocene with ultra‐robust oil solubility as multifunctional organometallic additive

Tailoring of organometallics structure toward desirable properties continues to be both fascinating and challenging in the field of materials science. Herein, a novel ferrocene derivative with long straight‐chain alkane mono‐substituent is synthesized and used as multifunctional organometallic additive in the base oil. This ferrocene‐based organometallic compound (MFc) is synthesized via the Friedel‐Crafts acylation of ferrocene with myristyl chloride, followed by reduction with sodium borohydride. The chemical structure, crystallizability, surface morphology, and the thermal properties of the as‐synthesized compound are systematically characterized. As the iron‐containing standard substance, the MFc was preferable dissolve in lubricating oil with the iron element content as high as 2*105 ppm. Resultantly, the MFc/oil solutions exhibited excellent stability even after high‐speed centrifugal treatment, long‐term storage up to 3 months, and ultra‐low temperature treatment at −40°C for 24 h. Moreover, the MFc as a functional lubricant additive could reduce the average wear scar diameter, wear volume, and coefficient of friction with 40%, 73%, and 18%, respectively, as compared to the corresponding pure base oil. This synthetic strategy provides a novel perspective for the design of functional organometallics, and the as‐synthesized novel ferrocene derivative may find a wide range of advanced potential applications in analytical chemistry, tribology, and interfacial science.

Nano-Engineered HfO2-Au photonic sensor for ultra-sensitive refractive index detection

In this study, we introduce a novel hafnium dioxide (HfO2) and thin gold layer based photonic crystal fiber (HfAu-PCF) sensor for refractive index measurement and optimize in the spectrum of 1.3 µm to 1.6 µm. The proposed sensor incorporates a D-shaped geometry for enhanced light-matter interaction, and the core of the fiber is surrounded by periodic air holes to facilitate efficient coupling of the guided mode with surface plasmons. The proposed HfAu-PCF sensor is geometrically optimized using finite element method (FEM) by fine-tuning air hole diameter, core size, layer thickness dimensions of the fiber to achieve performance stability. Leveraging the unique optical properties of HfO2 and Au, the sensor demonstrates superior performance metrics, achieving confinement loss (<10−6 dB/m), propagation constant (β) ∼ 6 × 106, V-Parameter < 2.3, a peak relative sensitivity of 99.05 % across the tested wavelength of 1.3 µm to 1.6 µm. Our findings reveal that choosing suitable parameters could lead to further enhancements in sensitivity, making the sensor for applications in bio-sensing, environmental monitoring, and chemical analysis, etc.

On Ve-Degree and Ev-Degree Based Topological Invariants of Chemical Structures

In the realm of graph theory, recent developments have introduced novel concepts, notably the ν ε -degree and ε ν -degree, offering expedited computations compared to traditional degree-based topological indices (TIs). These TIs serve as indispensable molecular descriptors for assessing chemical compound characteristics. This manuscript aims to meticulously compute a spectrum of TIs for silicon carbide S i C 4 - I [ r , s ] , with a specific focus on the ε ν -degree Zagreb index, the ν ε -degree Geometric-Arithmetic index, the ε ν -degree Randić index, the ν ε -degree Atom-bond connectivity index, the ν ε -degree Harmonic index, and the ν ε -degree Sum connectivity index. This study contributes to the ongoing advancement of graph theory applications in chemical compound analysis, elucidating the nuanced structural properties inherent in silicon carbide molecules.

Monosaccharide composition of lignocellulosic matrix—Optimization of microwave-assisted acid hydrolysis condition

Compositional analysis of polysaccharides is crucial in many applications of analytical chemistry, and typically involves hydrolysis as initial step, to break glycosidic bonds and release individual monosaccharide units. We developed a new method for the microwave-assisted acid hydrolysis of polysaccharides, here applied for determining the composition of the polysaccharide fraction within the lignocellulosic matrix of Pinus sylvestris. The optimisation of reaction conditions was carried out using a GC–MS method after a double-step sugar derivatization process.Under the optimized conditions, specifically, employing 2 M TFA, 40 min, and 120 °C, a high depolymerisation yield was achieved with minimal degradation. Furthermore, the amount of polysaccharides detected in pine wood aligns with the results in existing literature, substantiating the determined chemical composition.The synergy of microwave-assisted acid hydrolysis and full factorial design not only facilitated the determination of the optimal hydrolysis conditions but also enabled the assessment of the parameters influencing the polysaccharide hydrolysis process and their relationships. This approach made it feasible to achieve maximum hydrolysis efficiency while minimizing analyte degradation, employing a method that reduces environmental impact through the use of microwave energy. This strategy effectively reduced the required reaction temperature, time, and reagent quantities.

Introducing UV–visible spectroscopy at high school level following the historical evolution of spectroscopic instruments: a proposal for chemistry teachers

Spectroscopy is a scientific topic at the interface between Chemistry and Physics, which is taught at high school level in relation with its fundamental applications in Analytical Chemistry. In the first part of the paper, the topic of spectroscopy is analyzed having in mind the well-known Johnstone’s triangle of chemistry education, putting in evidence the way spectroscopy is usually taught at the three levels of chemical knowledge: macroscopic/phenomenological, sub-microscopic/molecular and symbolic ones. Among these three levels, following Johnstone’s recommendations the macroscopic one is the most useful for high school students who learn spectroscopy for the first time. Starting from these premises, in the second part of the paper, we propose a didactic sequence which is inspired by the historical evolution of spectroscopic instruments from the first spectroscopes invented by Gustav Kirchhoff and Robert Bunsen in 1860 to the UV–vis spectrophotometers which became common since the 1960s. The idea behind our research is to analyze the conceptual advancements through the history of spectroscopy and to identify the key episodes/experiments and spectroscopic instruments. For each of them, a didactic activity, typically an experiment, is then proposed underlining the relevant aspects from the chemistry education point of view. The present paper is the occasion to reflect on the potentialities of an historical approach combined with a laboratorial one, and to discuss the role of historical instruments and related technological improvements to teach spectroscopy.

Numerical Simulations of Combined Dielectrophoresis and Alternating Current Electrothermal Flow for High-Efficient Separation of (Bio)Microparticles.

High-efficient separation of (bio)microparticles has important applications in chemical analysis, environmental monitoring, drug screening, and disease diagnosis and treatment. As a label-free and high-precision separation scheme, dielectrophoresis (DEP) has become a research hotspot in microparticle separation, especially for biological cells. When processing cells with DEP, relatively high electric conductivities of suspending media are sometimes required to maintain the biological activities of the biosample, which results in high temperature rises within the system caused by Joule heating. The induced temperature gradient generates a localized alternating current electrothermal (ACET) flow disturbance, which seriously impacts the DEP manipulation of cells. Based on this, we propose a novel design of the (bio)microparticle separator by combining DEP with ACET flow to intensify the separation process. A coupling model that incorporates electric, fluid flow, and temperature fields as well as particle tracking is established to predict (bio)microparticle trajectories within the separator. Numerical simulations reveal that both ACET flow and DEP motion act in the same plane but in different directions to achieve high-precision separation between particles. This work provides new design ideas for solving the very tricky Joule heating interference in the DEP separation process, which paves the way for further improving the throughput of the DEP-based (bio)microparticle separation system.

Direct observation and elemental analysis of material nanoparticles in solution using scanning electron-assisted dielectric microscopy and EDS

High-resolution observation and elemental analysis of various particles in solution are important in the fields of materials, analytical chemistry, and industrial applications. Analysis of slurries of raw materials is essential for the development of highly functional materials. Recently, we have developed an SEM-based scanning electron assisted dielectric microscope (SE-ADM), which can directly observe biological samples and organic materials in aqueous solutions. Here, we have developed an SE-ADM system with the addition of energy-dispersive x-ray spectrometry that enables direct observation and elemental analysis of nanoparticles in solution. Using this system, we were able to directly observe and conduct elemental analysis of ceramic slurries and to clarify the dispersion state of alumina particles in solution, the distribution of binder, and the bonding state of silica and magnesium particles. Furthermore, our system can be applied to diverse liquid samples across a broad range of scientific and industrial fields, for example, nanotubes, organic specimens, batteries, and catalytic materials.

Near-IR Photoinduced Electrochemiluminescence Imaging with Structured Silicon Photoanodes.

Infrared (IR) imaging devices that convert IR irradiation (invisible to the human eye) to a visible signal are based on solid-state components. Here, we introduce an alternative concept based on light-addressable electrochemistry (i.e., electrochemistry spatially confined under the action of a light stimulus) that involves the use of a liquid electrolyte. In this method, the projection of a near-IR image (λexc = 850 or 840 nm) onto a photoactive Si-based photoanode, immersed into a liquid phase, triggers locally the photoinduced electrochemiluminescence (PECL) of the efficient [Ru(bpy)3]2+-TPrA system. This leads to the local conversion of near-IR light to visible (λPECL = 632 nm) light. We demonstrate that compared to planar Si photoanodes, the use of a micropillar Si array leads to a large enhancement of local light generation and considerably improves the resolution of the PECL image by preventing photogenerated minority carriers from diffusing laterally. These results are important for the design of original light conversion devices and can lead to important applications in photothermal imaging and analytical chemistry.

An all-inorganic lead-free metal halide double perovskite for the highly selective detection of norfloxacin in aqueous solution.

Lead-based perovskites are highly susceptible to environmental influences, and their application in analytical chemistry, especially in aqueous solution, has been reported rarely. All-inorganic lead-free metal halide perovskites have been considered as a substitute for lead-based perovskites. Herein, a Cs2RbTbCl6 perovskite microcrystal (PMCs), which emits strong yellow-green fluorescence with a maximum emission wavelength at 547nm, was for the first time synthesized and characterized. The Cs2RbTbCl6 PMCs could be well dispersed in N,N-dimethylacetamide (DMF), and its fluorescence could be significantly enhanced by the addition of norfloxacin (NOR) in the aqueous solution. We found that the Cs2RbTbCl6 PMCs can be used as fluorescent probes (excitation, 365nm; emission, 547nm) to selectively detect NOR in a concentration range from 10.0 to 200.0μM with the limit of detection (LOD) being 0.04μM. The Cs2RbTbCl6 PMCs could also be adsorbed on filter paper to fabricate as a fluorescent test paper for visual detection of NOR under 365-nm ultraviolet (UV) lamp irradiation. The proposed method has the potential to establish a new analytical method to visualize the detection of NOR in aqueous environments and also promotes the application of all-inorganic lead-free perovskites for analytical detection in aqueous environments.

Visualization-enhanced under-oil open microfluidic system for in situ characterization of multi-phase chemical reactions

Under-oil open microfluidic system, utilizing liquid-liquid boundaries for confinements, offers inherent advantages including clogging-free flow channels, flexible access to samples, and adjustable gas permeation, making it well-suited for studying multi-phase chemical reactions that are challenging for closed microfluidics. However, reports on the novel system have primarily focused on device fabrication and functionality demonstrations within biology, leaving their application in broader chemical analysis underexplored. Here, we present a visualization-enhanced under-oil open microfluidic system for in situ characterization of multi-phase chemical reactions with Raman spectroscopy. The enhanced system utilizes a semi-transparent silicon (Si) nanolayer over the substrate to enhance visualization in both inverted and upright microscope setups while reducing Raman noise from the substrate. We validated the system’s chemical stability and capability to monitor gas evolution and gas-liquid reactions in situ. The enhanced under-oil open microfluidic system, integrating Raman spectroscopy, offers a robust open-microfluidic platform for label-free molecular sensing and real-time chemical/biochemical process monitoring in multi-phase systems.

Reduced reverse degree-based topological indices of graphyne and graphdiyne nanoribbons with applications in chemical analysis

Graphyne and Graphdiyne Nanoribbons reveal significant prospective with diverse applications. In electronics, they propose unique electronic properties for high-performance nanoscale devices, while in catalysis, their excellent surface area and reactivity sort them valuable catalyst supports for numerous chemical reactions, contributing to progresses in sustainable energy and environmental remediation. The topological indices (TIs) are numerical invariants that provide important information about the molecular topology of a given molecular graph. These indices are essential in QSAR/QSPR analysis and play a significant role in predicting various physico-chemical characteristics. In this article, we present a formula for computing reduced reverse (RR) degree-based topological indices for graphyne and graphdiyne nanoribbons, including the RR Zagreb indices, RR hyper-Zagreb indices, RR forgotten index, RR atom bond connectivity index, and RR Geometric-arithmetic index. We also execute a graph-theoretical analysis and comparison to demonstrate the critical significance and validate the acquired results. Our findings provide insights into the structural and chemical properties of these nanoribbons and contribute to the development of new materials for various applications.

A bimetallic PtAu-modified carbon fiber electrochemical sensor for simultaneous and highly sensitive detection of catechol and hydroquinone in environmental water.

In this study, we report the development of a novel electrochemical sensor capable of the simultaneous detection of catechol (CC) and hydroquinone (HQ) through differential pulse voltammetry. The sensor is constructed using carbon fiber (CF) that has been intricately modified with bimetallic PtAu nanoparticles. The fabrication process involves subjecting CF to ultrasound treatment in an acidic mixture, resulting in the formation of activated carbon fiber (ACF). This activation step not only enhances surface roughness but also facilitates subsequent modification, ensuring the stability of the material. Bimetallic PtAu nanoparticles are then uniformly deposited onto the ACF surface through co-deposition from a metal precursor solution. The modified ACF, adorned with bimetallic PtAu nanoparticles, exhibits excellent conductivity and efficiently catalyzes both CC and HQ in a 10 mM phosphate-buffered saline solution at pH 7.0, thereby enabling their simultaneous detection. Under optimized experimental conditions, this electrochemical sensor achieves impressive detection limits of 0.019 μM for CC and 0.28 μM for HQ within the same concentration range of 0.5-50 μM, respectively. The practicality of the sensor is further demonstrated through recovery experiments using real water samples. This electrochemical sensor, with its superior performance and versatility, shows great potential for applications in analytical chemistry and environmental monitoring.

Cr2TiC2Tx MXene as an Adsorbent Material in Ultrasonic-Assisted d-µ-Solid Phase Extraction for Trace Detection of Heavy Metals

MXenes are a large family of two-dimensional transition metal carbides, nitrides, and carbonitrides. While MXenes have great potential for applications in analytical chemistry, most of the studies in this field...

Greenness assessment of analytical methods for determination of cannabinoids in oils using NEMI, Analytical Eco-Scale, AGREE and GAPI.

The cannabis plant is being increasingly researched due to its numerous therapeutic properties leading to the need for analytical techniques to assess substances present in extracts of the cannabis plant in carrier oils, such as medium chain triglycerides (MCT) oil. Awareness of the environmental impact of activities related to analysis led to the development of greenness assessment metrics. This study aimed to assess the environmental impact of analytical techniques applied in the analysis of cannabinoids in oil using Green Analytical Chemistry metrics. The first phase of the study consisted of a systematic literature review to identify high performance liquid chromatography and ultra high performance liquid chromatographic methods of analysis for cannabinoids in oil. In the second phase, the identified methods were assessed using the National Environmental Method Index (NEMI), Analytical Eco-scale, Analytical Greenness Calculator (AGREE) and Green Analytical Procedure Index (GAPI). Out of 124 identified studies, 8 were considered for the comparative analysis. The identified analytical methods consisted of high performance liquid chromatography (HPLC) using high resolution MS (n = 1), DAD (n = 2), UV (n = 1), UV and MS (n = 2) and MS/MS (n = 2) as detectors. When the analytical methods were assessed using the Analytical Eco-Scale, 7 out of 8 methods achieved a score ranging between 50 and 73, categorising them as acceptable green methods of analysis. One method achieved a total score of 80, categorising the method as an excellent green analysis. The application of Green Analytical Chemistry and respective metrics during the development of analytical methods contributes towards a reduction in the environmental footprint which results from related activities.

Intensified electrochemiluminescence and photoluminescence via supramolecular anion recognition interactions.

Herein, intensified electrochemiluminescence (ECL) and photoluminescence (PL) via supramolecular anion recognition interactions are demonstrated. A bisindolylpyrrole derivative with a structure containing two indole groups and 2-hexyl-pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione, BIPPD, was designed and synthesized de novo to induce the enhanced ECL and PL emission based on hydrogen bonding interactions with the dihydrogen phosphate anion. Remarkably, the ECL quantum efficiency and PL quantum yield were discovered to increase up to 5.5-fold and 1.5-fold, respectively, via this anion coordination. Dopant PF6 - was found not to form hydrogen bonds, while HSO4 - doping does slightly with the receptor molecule. There was no enhancement in either ECL or PL in both scenarios, revealing great recognition selectivity of the synthesized BIPPD. Mechanistic studies via 1H NMR, ECL, and PL spectra illustrated that the ECL processes varied in the presence and absence of H2PO4 - doping, thus leading to the understanding of enhanced efficiency. The bisindolylpyrrole derivative will find applications in supramolecular and analytical chemistry via controlled hydrogen bonding interactions.