ACS Measurement Science Au最新文献

Accurate and rapid analysis of chirality is crucial for understanding biological processes and molecular interactions, yet traditional vibrational circular dichroism (VCD) techniques are limited by long acquisition times and low throughput. We present a quantum cascade laser (QCL)-based VCD system that integrates a photoelastic modulator (PEM) with pulsed laser sources, using precise temporal synchronization and a novel calibration method based on Welch's power spectral density analysis. This hardware-software integration enables real-time demodulation without the need for conventional lock-in amplifiers and achieves accurate, high-SNR VCD spectra of α-pinene (±) mixtures with high reproducibility. Real-time enantiomeric excess determination is achieved with a 10× improvement in speed and a 5× enhancement in SNR compared to conventional VCD methods. These advancements pave the way for high-throughput and nondestructive chiral analysis, with potential applications in biosensing, structural biology, and pharmaceutical research.

In order to increase the lifetime of polymer electrolyte membrane (PEM) fuel cells (PEMFCs) and water electrolyzers (PEMWEs), understanding local degeneration processes in membrane electrode assemblies (MEAs) is crucial. By a combination of scanning electrochemical microscopy (SECM) with a flow-through diffusion cell (DiffC-DC-SECM) and ferrocyanide and protons as redox mediators, a spatially resolved analytical method was developed that can differentiate between different functional and structural degeneration phenomena in the aging process of a membrane. An SECM scan at cathodic potential detects the diffusion of protons through the membrane and thus its through-plane proton conductivity, while a second SECM scan at anodic potential visualizes the diffusion of the iron complex through the membrane, thus perforating structural damage such as cracks and holes. The method was successfully validated for the spatially resolved differentiation of membrane damage in pristine PEMs and catalyst-coated membranes (CCMs) with artificial holes, chemically aged CCMs, and MEAs in fully assembled operational PEMFCs aged by an open-circuit voltage membrane accelerated stress test. DiffC-DC-SECM thus provides a powerful technique with high local resolution for membrane integrity testing under realistic operation conditions to develop long-term durable materials for PEMFCs and PEMWEs.

The contamination of natural basins by agricultural or industrial activities, and the growing need for potable water due to climate changes accelerate the drive to find versatile, fast, practical, and easy-to-use methods for water analysis. A potentially versatile technique suitable for water analysis is Raman Spectroscopy (RS). Featured by good resolution but low sensitivity, RS detects molecular vibrational modes of an analyte in water. Nitrate is an indicator of chemical and/or biological pollution, it displays Raman active vibrational modes affected by the interaction with other systems in solution, allowing a wide range of applications. Concerning Nitrate analysis in water, a general introduction to the Raman effect and the basic instrumentation were herein discussed. RS is a potential solution to wastewater analysis. This review first reports the theoretical background of the technique and its basic working principles, then, the state-of-the-art scientific contributions related to Nitrate detection are investigated with a particular interest in the instrumental setup and the chemometric techniques employed to improve its sensitivity. In the studies hereby considered, instrumental setup (for example, laser frequency, laser power, acquisition times) and different technical solutions (for example, micro- versus macro-Raman instruments) to increase the technique’s sensitivity on Nitrate detection are described. Concisely, the use of deep-UV lasers, optically active Surface-Enhanced Raman Spectroscopy (SERS) or Fiber-Enhanced Raman spectroscopy (FERS) equipment, coupled with instrumental settings, i.e. acquisition time, variable temperature of acquisition, use of special sampling apparatus (cuvettes or immersion probes), or with ion exchange resins for analyte enrichment, have been reported. Remarkably, examples of large data correction of unwanted fluorescence by mathematical processing or chemical quenching were reported too, suggesting solutions for the Raman analysis of wastewaters. Finally, a short digression on Machine Learning (ML) applied to RS is proposed, showing the promising results reported in other fields. Data-driven methods could be a solution to improve the low sensitivity of the RS for Nitrate detection. Hence, an approach of ML methods for the typical RS spectra processing (spike removal, baseline correction, fluorescence curve elimination, instrumental noise correction) was hereby mentioned, suggesting an improvement in the detection capability of Nitrate ion in water.

A surface-acoustic-wave-driven microactuator that allows separation of the piezoelectric substrate and chip has been fabricated and characterized. By simply placing the microactuator on a disposable chip, the microactuator did not contaminate the substrate with any reagent and could easily transport droplets and powders. The microactuator also allowed mixing of heterophase materials, such as powder and droplets, in a microfluidic well to increase their chemical reaction. This microactuator will enable significant cost savings and automation of plants and research facilities.

Phosphorylation and glycosylation are two important protein post-transitional modifications (PTMs). However, quantification of these PTMs is challenging due to the lack of protein or peptide standards. In this study, we introduced a novel approach using coulometric mass spectrometry (CMS) for absolute quantitation of phosphopeptides and glycopeptides without using standards. First, phosphorylated tyrosine peptides such as TSTEPQpYQPGENL and RRLIEDAEpYAARG can be converted into electrochemically active tyrosine peptides via enzymatic phosphate removal using alkaline phosphatase prior to CMS quantitation. Accurate quantitation was obtained with small quantitation errors (0.3–6.6%). Alternatively, for electrochemically inactive phosphopeptides and glycopeptides, derivatization of their N-termini with an NHS ester reagent, 2,5-dioxo-1-pyrrolidinyl 3,4-dihydroxybenzene propanoate (DPDP), was conducted to introduce one electroactive catechol tag, allowing the DPDP-derivatized peptides to be quantified by CMS. This strategy was first validated using peptides RGD, GGYR, phosphopeptide RRApSVA, and glycopeptide NYIVGQPSS(β-GlcNAc)TGNL–OH, and successful quantification was achieved with quantification errors less than 6%. Taking one step further, we applied this approach to quantify glycopeptides generated from tryptic digestion of the NIST monoclonal antibody (mAb). Through hydrophilic interaction liquid chromatography column separation, five N297 glycopeptides were successfully derivatized, separated, and quantified by CMS without the use of standards. Due to the biological significance of PTMs, this study for quantifying peptides carrying PTMs would have a high potential for quantitative proteomics and biological research.

Screen-printed electrodes (SPEs) are an innovative technology in electrochemical sensors, offering advantages such as easy fabrication, large-scale production, low cost, and potential for miniaturization. These electrodes can be disposable and customized for various applications. Due to these advantages, SPEs are gaining attention in fields such as medicine and pharmacy. In this study, an electrochemical sensor was developed through screen-printing, using new conductive ink, compounded with carbon black, Chinese shellac, and acetone. The device was characterized by different approaches to analyze its characteristics, including scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry, and contact angle. Also, the electrochemical characterizations were performed by using cyclic voltammetry and impedance spectroscopy. The sensor was employed to detect melatonin, a sleep-regulating hormone, and, under optimized parameters, the analytical curve by differential pulse voltammetry exhibited a linear range from 1.0 to 100 μmol L^–1, with a limit of detection of 0.1 μmol L^–1. The device was applied to synthetic urine samples using the addition and recovery method, yielding recovery values from 86.7 to 110%. The results indicate that the conductive ink is suitable for manufacturing printed electrodes, and the device proved promising for melatonin detection.

The development of enzyme-based bioelectronic devices, including biosensors and biomimetic systems, has significantly advanced with the introduction of innovative materials such as hydrogels, deep eutectic solvents (DES), and ionic liquids (ILs). These materials offer unique advantages in enhancing biodevice performance, particularly in enzyme stabilization, biocompatibility, and electrochemical sensitivity. Hydrogels, known for their high water content and flexibility, provide an ideal matrix for enzyme immobilization in biological applications but are limited by low ionic conductivity. DES, with their green chemistry credentials and ability to stabilize enzymes under harsh conditions, show great promise, although scalability and performance in complex biological systems remain challenges. ILs, with their superior electron transfer capabilities, enable high sensitivity in electrochemical biosensors, though issues of viscosity and potential toxicity need to be addressed for broader biomedical use. This review provides a comparative analysis of the roles of these materials in enzyme-based biosensors and bioelectronics, including microbatteries and bioelectrosynthesis, highlighting their respective strengths, limitations, and future opportunities. The integration of these materials holds great potential for advancing bioelectronics technologies, with applications spanning medical diagnostics, environmental monitoring, and industrial processes. By addressing current challenges and optimizing these materials for large-scale use, the future of enzyme-based devices could see significant improvements in efficiency, sensitivity, and sustainability.

Tafel analysis is widely used to characterize electrode kinetics. The technique has found use in electrochemistry, catalysis, materials, and corrosion research. Accurate Tafel analysis is especially critical in comparison of electrocatalysts. However, classical Tafel analysis (CTA) relies on the user’s subjective selection of a linear range in the Tafel plot; dependent on linear regression of the user-selected range, kinetic parameters can vary by orders of magnitude. As use of CTA in the literature grows, a need is identified for more reliable, user-independent Tafel analysis. Here, Taffit, an algorithm constructed in the widely available Microsoft Excel, is presented. Taffit generates a Tafel plot from linear sweep voltammetric data and determines the exchange current density j₀, charge transfer coefficient α, and Tafel slopes by closest statistical fit. Comparisons between Taffit and CTA are made for the hydrogen evolution reaction (HER, 2H⁺ + 2e ⇌ H₂) on glassy carbon (GC) and platinum electrodes. Taffit finds log j₀ values of −7.2 and −3.9 for GC and Pt under H₂ at pH 0, as measured without resistive compensation. This is the first report of j₀ for HER on GC. Because algorithmic fitting in the low overpotential region uses both cathodic and anodic branches of the Tafel plot, Taffit has greater precision than CTA. Agreement is also shown between literature values reported by CTA and those obtained by Taffit for HER on metal phosphide and selenide electrocatalysts. The Taffit algorithm substantially reduces subjectivity to improve the accuracy and precision of Tafel analysis.

In the United States, ∼30,000 units of red blood cells (RBCs) are transfused daily to patient recipients. These RBCs are stored in one of multiple variations of media known as additive solutions, all of which contain glucose at concentrations well above physiological levels. Recently, strategies for storage of the RBCs in normoglycemic versions of the additive solutions whose glucose levels are maintained with periodic boluses of glucose were developed, resulting in benefits to the stored RBCs. Here, we describe a system capable of semiautonomous, Wi-Fi-enabled control of glucose delivery using a microperistaltic pump for maintenance of physiological concentrations of glucose in a closed RBC storage system. The RBCs stored in these normoglycemic conditions demonstrated reduced lysis and reduced hemoglobin glycation in comparison to those of the currently used hyperglycemic additive solutions. Furthermore, a novel single cell technique using pressure-induced conductivity mapping showed an improved Young’s modulus for those RBCs stored in normoglycemic solutions. These quantitative measurements of the RBCs’ chemical and physical properties coincide with improvements in cell functionality. Specifically, determinations of RBC-derived ATP using a 3D-printed microfluidic device show an increased release of ATP for RBCs stored in normoglycemic solutions in comparison to hyperglycemic storage, even for cells that were 2 weeks past a storage expiration of 42 days.